Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18874094  32 DVSQYHVNHLVTFCLGEEDGVHTVEDASRKLAVMDSQGRVWAQEMLLRVSPSQVTLLDPVSKEELESYPLDAIVRCDAVM 111
Cdd:cd01210   1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETKEELESFPLSSIQECTAVL 80

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|.
gi 18874094 112 PRGRSRSLLLLVCQEPERAQPDVHFFQGLLLGAELIREDIQGALQNYRSGR 162
Cdd:cd01210  81 STCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

Src Homology 3 domain of Epidermal growth factor receptor kinase substrate 8 and similar proteins; This group is composed of Eps8 and Eps8-like proteins including Eps8-like 1-3, among others. These proteins contain N-terminal Phosphotyrosine-binding (PTB), central SH3, and C-terminal effector domains. Eps8 binds either Abi1 (also called E3b1) or Rab5 GTPase activating protein RN-tre through its SH3 domain. With Abi1 and Sos1, it becomes part of a trimeric complex that is required to activate Rac. Together with RN-tre, it inhibits the internalization of EGFR. The SH3 domains of Eps8 and similar proteins recognize peptides containing a PxxDY motif, instead of the classical PxxP motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|...
gi 18874094 481 WVLCNYDFQARNGSELSVKHRDVLEVLDDRRKWWKVRDHQGQEGYVPYNILTP 533
Cdd:cd11764   1 YVRVLYDFTARNSKELSVLKGEYLEVLDDSRQWWKVRNSRGQVGYVPHNILEP 53

Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18874094  32 DVSQYHVNHLVTFCLGEEDGVHTVEDASRKLAVMDSQGRVWAQEMLLRVSPSQVTLLDPVSKEELESYPLDAIVRCDAVM 111
Cdd:cd01210   1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETKEELESFPLSSIQECTAVL 80

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|.
gi 18874094 112 PRGRSRSLLLLVCQEPERAQPDVHFFQGLLLGAELIREDIQGALQNYRSGR 162
Cdd:cd01210  81 STCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

SAM domain of EPS8-like subfamily; SAM (sterile alpha motif) domain of EPS8-like subfamily is a putative protein-protein interaction domain. This subfamily includes epidermal growth factor receptor kinase substrate 8 proteins (EPS8) and epidermal growth factor receptor kinase substrate 8-like (EPSL8) 1, 2, 3 proteins with the SAM domain located in the C-terminal effector region. This region is responsible for intracellular protein localization and is involved in small GTPases (such as Rac and Rab5) activation/inhibition. Proteins belonging to this group participate in coordination and integration of multiple signaling pathways; in particular, they play a role in the control of actin dynamics and in receptor endocytosis. They can form complexes with other proteins; for example, in the actin signaling network they interact with SOS1 and E3b1 (Abl1) proteins as well as with CRIB (via SH3 domains) during the actin filament formation, and in the receptor endocytosis their partner is RN-tre protein.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 18874094 622 QLSPRSEASVVRAWLQTKGFSSGTVEALGVLTGAQLFSLQKEELRAVCPEEGARVYSQVTVQRALL 687
Cdd:cd09540   1 PLTYDSSPEEVKAWLQAKGFSKITVRSLGVLTGAQLFSLNKEELKTVCPEEGARVYSQLTVQKSAL 66

SAM domain (Sterile alpha motif);

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 18874094   620 EPQLSPRSEASVVRAWLQTKGFSSGTVEALGVLTGAQLFSLQKEELRAVCP-EEGARVYSQVT 681
Cdd:pfam18016   3 SINITPKSTPEEVQAWLTAKGFSKKTVKSLGTLSGAQLFSLSKEELKQICGpAEGIRLYSQLL 65

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|...
gi 18874094   486 YDFQARNGSELSVKHRDVLEVLDD-RRKWWKVRDHQGQEGYVP 527
Cdd:pfam00018   4 YDYTAQEPDELSFKKGDIIIVLEKsEDGWWKGRNKGGKEGLIP 46

Uncharacterized conserved protein YgiM, contains N-terminal SH3 domain, DUF1202 family [General function prediction only];

                        10        20        30        40
                ....*....|....*....|....*....|....*....|...
gi 18874094 497 SVKHRDVLEVLDDRRKWWKVRDHQGQEGYVPYNILTPHPGPQV 539
Cdd:COG3103  29 TLPKGEKVTVLGRSGGWYKVRYSNGKTGWVSSRYLTVTPSARE 71

Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18874094  32 DVSQYHVNHLVTFCLGEEDGVHTVEDASRKLAVMDSQGRVWAQEMLLRVSPSQVTLLDPVSKEELESYPLDAIVRCDAVM 111
Cdd:cd01210   1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETKEELESFPLSSIQECTAVL 80

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|.
gi 18874094 112 PRGRSRSLLLLVCQEPERAQPDVHFFQGLLLGAELIREDIQGALQNYRSGR 162
Cdd:cd01210  81 STCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

SAM domain of EPS8-like subfamily; SAM (sterile alpha motif) domain of EPS8-like subfamily is a putative protein-protein interaction domain. This subfamily includes epidermal growth factor receptor kinase substrate 8 proteins (EPS8) and epidermal growth factor receptor kinase substrate 8-like (EPSL8) 1, 2, 3 proteins with the SAM domain located in the C-terminal effector region. This region is responsible for intracellular protein localization and is involved in small GTPases (such as Rac and Rab5) activation/inhibition. Proteins belonging to this group participate in coordination and integration of multiple signaling pathways; in particular, they play a role in the control of actin dynamics and in receptor endocytosis. They can form complexes with other proteins; for example, in the actin signaling network they interact with SOS1 and E3b1 (Abl1) proteins as well as with CRIB (via SH3 domains) during the actin filament formation, and in the receptor endocytosis their partner is RN-tre protein.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 18874094 622 QLSPRSEASVVRAWLQTKGFSSGTVEALGVLTGAQLFSLQKEELRAVCPEEGARVYSQVTVQRALL 687
Cdd:cd09540   1 PLTYDSSPEEVKAWLQAKGFSKITVRSLGVLTGAQLFSLNKEELKTVCPEEGARVYSQLTVQKSAL 66

SAM domain (Sterile alpha motif);

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 18874094   620 EPQLSPRSEASVVRAWLQTKGFSSGTVEALGVLTGAQLFSLQKEELRAVCP-EEGARVYSQVT 681
Cdd:pfam18016   3 SINITPKSTPEEVQAWLTAKGFSKKTVKSLGTLSGAQLFSLSKEELKQICGpAEGIRLYSQLL 65

First Src Homology 3 domain of Nck adaptor proteins; Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2 (also called Nckbeta or Growth factor receptor-bound protein 4, Grb4), which show partly overlapping functions but also bind distinct targets. Their SH3 domains are involved in recruiting downstream effector molecules, such as the N-WASP/Arp2/3 complex, which when activated induces actin polymerization that results in the production of pedestals, or protrusions of the plasma membrane. The first SH3 domain of Nck proteins preferentially binds the PxxDY sequence, which is present in the CD3e cytoplasmic tail. This binding inhibits phosphorylation by Src kinases, resulting in the downregulation of TCR surface expression. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*...
gi 18874094 482 VLCNYDFQARNGSELSVKHRDVLEVLDDRRKWWKVRDHQGQEGYVPYN 529
Cdd:cd11765   2 VVAKYDYTAQGDQELSIKKNEKLTLLDDSKHWWKVQNSSNQTGYVPSN 49

Src Homology 3 domain of Tec-like Protein Tyrosine Kinases; The Tec (Tyrosine kinase expressed in hepatocellular carcinoma) subfamily is composed of Tec, Btk, Bmx (Etk), Itk (Tsk, Emt), Rlk (Txk), and similar proteins. They are cytoplasmic (or nonreceptor) tyr kinases containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Most Tec subfamily members (except Rlk) also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. In addition, some members contain the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. Tec kinases are expressed mainly by haematopoietic cells, although Tec and Bmx are also found in endothelial cells. B-cells express Btk and Tec, while T-cells express Itk, Txk, and Tec. Collectively, Tec kinases are expressed in a variety of myeloid cells such as mast cells, platelets, macrophages, and dendritic cells. Each Tec kinase shows a distinct cell-type pattern of expression. The function of Tec kinases in lymphoid cells have been studied extensively. They play important roles in the development, differentiation, maturation, regulation, survival, and function of B-cells and T-cells. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*....
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRK-WWKVRDHQGQEGYVPYNILTP 533
Cdd:cd11768   6 YDFQPIEPGDLPLEKGEEYVVLDDSNEhWWRARDKNGNEGYIPSNYVTE 54

Src homology 3 domain of Src kinase-like Protein Tyrosine Kinases; Src subfamily members include Src, Lck, Hck, Blk, Lyn, Fgr, Fyn, Yrk, Yes, and Brk. Src (or c-Src) proteins are cytoplasmic (or non-receptor) PTKs which are anchored to the plasma membrane. They contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Brk lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. They were identified as the first proto-oncogene products, and they regulate cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Src kinases are overexpressed in a variety of human cancers, making them attractive targets for therapy. They are also implicated in acute inflammatory responses and osteoclast function. Src, Fyn, Yes, and Yrk are widely expressed, while Blk, Lck, Hck, Fgr, Lyn, and Brk show a limited expression pattern. This subfamily also includes Drosophila Src42A, Src oncogene at 42A (also known as Dsrc41) which accumulates at sites of cell-cell or cell-matrix adhesion, and participates in Drosphila development and wound healing. It has been shown to promote tube elongation in the tracheal system, is essential for proper cell-cell matching during dorsal closure, and regulates cell-cell contacts in developing Drosophila eyes. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*..
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRdHQ--GQEGYVPYN 529
Cdd:cd11845   6 YDYEARTDDDLSFKKGDRLQILDDSDgDWWLAR-HLstGKEGYIPSN 51

Phosphotyrosine-binding domain, phosphotyrosine-interaction (PI) domain; PTB/PI domain structure similar to those of pleckstrin homology (PH) and IRS-1-like PTB domains.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 18874094     35 QYHVNHLVTFCLGEEDGVHTVEDASRKLAVMDSQGRVWAQEMLLRVSPSQVTLLDPVSKEELESYPLDAIVRCDAVMPRG 114
Cdd:smart00462   5 SFRVKYLGSVEVPEARGLQVVQEAIRKLRAAQGSEKKEPQKVILSISSRGVKLIDEDTKAVLHEHPLRRISFCAVGPDDL 84

                           90       100
                   ....*....|....*....|....
gi 18874094    115 RsrsLLLLVCQEPERAQPDVHFFQ 138
Cdd:smart00462  85 D---VFGYIARDPGSSRFACHVFR 105

Src homology 3 domain of Apoptosis Stimulating of p53 proteins (ASPP); The ASPP family of proteins bind to important regulators of apoptosis (p53, Bcl-2, and RelA) and cell growth (APCL, PP1). They share similarity at their C-termini, where they harbor a proline-rich region, four ankyrin (ANK) repeats, and an SH3 domain. Vertebrates contain three members of the family: ASPP1, ASPP2, and iASPP. ASPP1 and ASPP2 activate the apoptotic function of the p53 family of tumor suppressors (p53, p63, and p73), while iASPP is an oncoprotein that specifically inhibits p53-induced apoptosis. The expression of ASPP proteins is altered in tumors; ASPP1 and ASPP2 are downregulated whereas iASPP is upregulated is some cancer types. ASPP proteins also bind and regulate protein phosphatase 1 (PP1), and this binding is competitive with p53 binding. The SH3 domain and the ANK repeats of ASPP contribute to the p53 binding site; they bind to the DNA binding domain of p53. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL----DDRRKWWKVRdHQGQEGYVPYNIL 531
Cdd:cd11807   7 FDYEAENGDELSFREGDELTVLrkgdDDETEWWWAR-LNDKEGYVPRNLL 55

First Src Homology 3 domain of FCH and double SH3 domains proteins; This group is composed of FCH and double SH3 domains protein 1 (FCHSD1) and FCHSD2. These proteins have a common domain structure consisting of an N-terminal F-BAR (FES-CIP4 Homology and Bin/Amphiphysin/Rvs), two SH3, and C-terminal proline-rich domains. They have only been characterized in silico and their functions remain unknown. This group also includes the insect protein, nervous wreck, which acts as a regulator of synaptic growth signaling. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*....
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL--DDRRKWWKVRDHQGQEGYVPYNILT 532
Cdd:cd11761   8 YSYEAQRPDELTITEGEELEVIedGDGDGWVKARNKSGEVGYVPENYLQ 56

First Src Homology 3 domain of Nck2 adaptor protein; Nck2 (also called Nckbeta or Growth factor receptor-bound protein 4, Grb4) plays a crucial role in connecting signaling pathways of tyrosine kinase receptors and important effectors in actin dynamics and cytoskeletal remodeling. It binds neuronal signaling proteins such as ephrinB and Disabled-1 (Dab-1) exclusively. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2, which show partly overlapping functions but also bind distinct targets. The first SH3 domain of Nck2 binds the PxxDY sequence in the CD3e cytoplasmic tail; this binding inhibits phosphorylation by Src kinases, resulting in the downregulation of TCR surface expression. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*...
gi 18874094 482 VLCNYDFQARNGSELSVKHRDVLEVLDDRRKWWKVRDHQGQEGYVPYN 529
Cdd:cd11899   6 VIAKWDYTAQQDQELDIKKNERLWLLDDSKTWWRVRNAANRTGYVPSN 53

Second C-terminal Src homology 3 domain of Dynamin Binding Protein, also called Tuba, and similar domains; DNMBP or Tuba is a cdc42-specific guanine nucleotide exchange factor (GEF) that contains four N-terminal SH3 domains, a central RhoGEF [or Dbl homology (DH)] domain followed by a Bin/Amphiphysin/Rvs (BAR) domain, and two C-terminal SH3 domains. It provides a functional link between dynamin, Rho GTPase signaling, and actin dynamics. It plays an important role in regulating cell junction configuration. The C-terminal SH3 domains of DNMBP bind to N-WASP and Ena/VASP proteins, which are key regulatory proteins of the actin cytoskeleton. Also included in this subfamily is the second C-terminal SH3 domain of Rho guanine nucleotide exchange factor 37 (ARHGEF37), whose function is still unknown. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|...
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLD--DRR---KWWKVRDHqGQEGYVPYNILTP 533
Cdd:cd11800   6 YTFEARSPGELSVTEGQVVTVLEkhDLKgnpEWWLVEDR-GKQGYVPSNYLAK 57

Src Homology 3 domain of Tec (Tyrosine kinase expressed in hepatocellular carcinoma); Tec is a cytoplasmic (or nonreceptor) tyr kinase containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation, and the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. It is more widely-expressed than other Tec subfamily kinases. Tec is found in endothelial cells, both B- and T-cells, and a variety of myeloid cells including mast cells, erythroid cells, platelets, macrophages and neutrophils. Tec is a key component of T-cell receptor (TCR) signaling, and is important in TCR-stimulated proliferation, IL-2 production and phospholipase C-gamma1 activation. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|..
gi 18874094 482 VLCNYDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRDHQGQEGYVPYNILT 532
Cdd:cd11905   3 VVAMYDFQPTEPHDLRLETGEEYVILEKNDvHWWKARDKYGKEGYIPSNYVT 54

Src homology 3 domain of Signal Transducing Adaptor Molecules; STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. There are two vertebrate STAMs, STAM1 and STAM2, which may be functionally redundant; vertebrate STAMs contain ITAM motifs. They are part of the endosomal sorting complex required for transport (ESCRT-0). STAM2 deficiency in mice did not cause any obvious abnormality, while STAM1 deficiency resulted in growth retardation. Loss of both STAM1 and STAM2 in mice proved lethal, indicating that STAMs are important for embryonic development. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*...
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRDHQGqEGYVPYNILT 532
Cdd:cd11820   7 YDFEAAEDNELTFKAGEIITVLDDSDpNWWKGSNHRG-EGLFPANFVT 53

Src homology 3 domain of Signal Transducing Adaptor Molecule 1; STAM1 is part of the endosomal sorting complex required for transport (ESCRT-0) and is involved in sorting ubiquitinated cargo proteins from the endosome. It may also be involved in the regulation of IL2 and GM-CSF mediated signaling, and has been implicated in neural cell survival. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|..
gi 18874094 482 VLCNYDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRDHQGQeGYVPYNILT 532
Cdd:cd11964   3 VRAIYDFEAAEDNELTFKAGDIITILDDSDpNWWKGETPQGT-GLFPSNFVT 53

N-terminal Src homology 3 domain of GRB2-related adaptor protein 2; GRAP2 is also called GADS (GRB2-related adapter downstream of Shc), GrpL, GRB2L, Mona, or GRID (Grb2-related protein with insert domain). It is expressed specifically in the hematopoietic system. It plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. It also have roles in antigen-receptor and tyrosine kinase mediated signaling. GRAP2 is unique from other GRB2-like adaptor proteins in that it can be regulated by caspase cleavage. It contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The N-terminal SH3 domain of the related protein GRB2 binds to Sos and Sos-derived proline-rich peptides. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*.
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRKWWKVRDHqGQEGYVPYNIL 531
Cdd:cd11947   6 FDFTASGEDELSFKKGDVLKILSSDDIWFKAELN-GEEGYVPKNFV 50

Src Homology 3 domain of C-terminal Src kinase; CSK is a cytoplasmic (or nonreceptor) tyr kinase containing the Src homology domains, SH3 and SH2, N-terminal to the catalytic tyr kinase domain. They negatively regulate the activity of Src kinases that are anchored to the plasma membrane. To inhibit Src kinases, CSK is translocated to the membrane via binding to specific transmembrane proteins, G-proteins, or adaptor proteins near the membrane. CSK catalyzes the tyr phosphorylation of the regulatory C-terminal tail of Src kinases, resulting in their inactivation. It is expressed in a wide variety of tissues and plays a role, as a regulator of Src, in cell proliferation, survival, and differentiation, and consequently, in cancer development and progression. In addition, CSK also shows Src-independent functions. It is a critical component in G-protein signaling, and plays a role in cytoskeletal reorganization and cell migration. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 482 VLCNYDFQARNGSELSVKHRDVLEVLDDRR--KWWKVRDHQGQEGYVPYN 529
Cdd:cd11769   4 CIAKYNFNGASEEDLPFKKGDILTIVAVTKdpNWYKAKNKDGREGMIPAN 53

Src homology 3 domain of Brk (Breast tumor kinase) Protein Tyrosine Kinase (PTK), also called PTK6; Brk is a cytoplasmic (or non-receptor) PTK with limited homology to Src kinases. It has been found to be overexpressed in a majority of breast tumors. It plays roles in normal cell differentiation, proliferation, survival, migration, and cell cycle progression. Brk substrates include RNA-binding proteins (SLM-1/2, Sam68), transcription factors (STAT3/5), and signaling molecules (Akt, paxillin, IRS-4). Src kinases in general contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr; they are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Brk lacks the N-terminal myristoylation site. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|.
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRKWWKVR--DHQGQ---EGYVPYNIL 531
Cdd:cd11847   6 WDFKARGDEELSFQAGDQFRIAERSGDWWTALklDRAGGvvaQGFVPNNYL 56

N-terminal Src homology 3 domain of Growth factor receptor-bound protein 2 (GRB2) and related proteins; This family includes the adaptor protein GRB2 and related proteins including Drosophila melanogaster Downstream of receptor kinase (DRK), Caenorhabditis elegans Sex muscle abnormal protein 5 (Sem-5), GRB2-related adaptor protein (GRAP), GRAP2, and similar proteins. Family members contain an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. GRB2/Sem-5/DRK is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. GRAP2 plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. GRAP acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. The N-terminal SH3 domain of GRB2 binds to Sos and Sos-derived proline-rich peptides. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*.
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL--DDRRKWWKVrDHQGQEGYVPYN 529
Cdd:cd11804   6 HDFKATAEDELSFKKGSILKVLnmEDDPNWYKA-ELDGKEGLIPKN 50

Src Homology 3 domain of Bruton's tyrosine kinase; BTK is a cytoplasmic (or nonreceptor) tyr kinase containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation, and the Tec homology (TH) domain with proline-rich and zinc-binding regions. Btk is expressed in B-cells, and a variety of myeloid cells including mast cells, platelets, neutrophils, and dendrictic cells. It interacts with a variety of partners, from cytosolic proteins to nuclear transcription factors, suggesting a diversity of functions. Stimulation of a diverse array of cell surface receptors, including antigen engagement of the B-cell receptor (BCR), leads to PH-mediated membrane translocation of Btk and subsequent phosphorylation by Src kinase and activation. Btk plays an important role in the life cycle of B-cells including their development, differentiation, proliferation, survival, and apoptosis. Mutations in Btk cause the primary immunodeficiency disease, X-linked agammaglobulinaemia (XLA) in humans. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|....
gi 18874094 480 KWVLCNYDFQARNGSELSVKHRDVLEVLDD-RRKWWKVRDHQGQEGYVPYNILT 532
Cdd:cd11906   1 KKVVALYDYTPMNAQDLQLRKGEEYVILEEsNLPWWRARDKNGREGYIPSNYVT 54

Src homology 3 domain of Yes Protein Tyrosine Kinase; Yes (or c-Yes) is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. c-Yes kinase is the cellular homolog of the oncogenic protein (v-Yes) encoded by the Yamaguchi 73 and Esh sarcoma viruses. It displays functional overlap with other Src subfamily members, particularly Src. It also shows some unique functions such as binding to occludins, transmembrane proteins that regulate extracellular interactions in tight junctions. Yes also associates with a number of proteins in different cell types that Src does not interact with, like JAK2 and gp130 in pre-adipocytes, and Pyk2 in treated pulmonary vein endothelial cells. Although the biological function of Yes remains unclear, it appears to have a role in regulating cell-cell interactions and vesicle trafficking in polarized cells. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRD-HQGQEGYVPYNILTP 533
Cdd:cd12007   7 YDYEARTTEDLSFKKGERFQIINNTEgDWWEARSiATGKNGYIPSNYVAP 56

Third Src Homology 3 domain of Nck1 adaptor protein; Nck1 (also called Nckalpha) plays a crucial role in connecting signaling pathways of tyrosine kinase receptors and important effectors in actin dynamics and cytoskeletal remodeling. It binds and activates RasGAP, resulting in the downregulation of Ras. It is also involved in the signaling of endothilin-mediated inhibition of cell migration. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2, which show partly overlapping functions but also bind distinct targets. The third SH3 domain of Nck appears to prefer ligands with a PxAPxR motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLD---DRRKWWKVRDHQGQEGYVPYNILT 532
Cdd:cd11904   7 YPFSSSNDEELNFEKGEVMDVIEkpeNDPEWWKCRKANGQVGLVPKNYVT 56

Src Homology 3 domain of Nephrocystin (or Nephrocystin-1); Nephrocystin contains an SH3 domain involved in signaling pathways that regulate cell adhesion and cytoskeletal organization. It is a protein that in humans is associated with juvenile nephronophthisis, an inherited kidney disease characterized by renal fibrosis that lead to chronic renal failure in children. It is localized in cell-cell junctions in renal duct cells, and is known to interact with Ack1, an activated Cdc42-associated kinase. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|...
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRK-WWKVRDHQGQEGYVP 527
Cdd:cd11770   6 SDFQAEQEGDLSFKKGEVLRIISKRADgWWLAENSKGNRGLVP 48

Src Homology 3 domain of Sorting Nexin 9 and similar proteins; Sorting nexins (SNXs) are Phox homology (PX) domain containing proteins that are involved in regulating membrane traffic and protein sorting in the endosomal system. SNXs differ from each other in their lipid-binding specificity, subcellular localization and specific function in the endocytic pathway. This subfamily consists of SH3 domain containing SNXs including SNX9, SNX18, SNX33, and similar proteins. SNX9 is localized to plasma membrane endocytic sites and acts primarily in clathrin-mediated endocytosis, while SNX18 is localized to peripheral endosomal structures, and acts in a trafficking pathway that is clathrin-independent but relies on AP-1 and PACS1. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*
gi 18874094 485 NYDFQARNGSELSVKHRDVLEVL--DDRRKWWKVRDHQGQEGYVP 527
Cdd:cd11763   5 LYDFDSQPSGELSLRAGEVLTITrqDVGDGWLEGRNSRGEVGLFP 49

N-terminal Src homology 3 domain of GRB2-related adaptor protein; GRAP is a GRB-2 like adaptor protein that is highly expressed in lymphoid tissues. It acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. It has been identified as a regulator of TGFbeta signaling in diabetic kidney tubules and may have a role in the pathogenesis of the disease. GRAP contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The N-terminal SH3 domain of the related protein GRB2 binds to Sos and Sos-derived proline-rich peptides. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*.
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL--DDRRKWWKVrDHQGQEGYVPYN 529
Cdd:cd11948   6 YSFQATESDELPFQKGDILKILnmEDDQNWYKA-ELQGREGYIPKN 50

Src homology 3 domain of SH3 protein interacting with Nck, 90 kDa (SPIN90); SPIN90 is also called NCK interacting protein with SH3 domain (NCKIPSD), Dia-interacting protein (DIP), 54 kDa vimentin-interacting protein (VIP54), or WASP-interacting SH3-domain protein (WISH). It is an F-actin binding protein that regulates actin polymerization and endocytosis. It associates with the Arp2/3 complex near actin filaments and determines filament localization at the leading edge of lamellipodia. SPIN90 is expressed in the early stages of neuronal differentiation and plays a role in regulating growth cone dynamics and neurite outgrowth. It also interacts with IRSp53 and regulates cell motility by playing a role in the formation of membrane protrusions. SPIN90 contains an N-terminal SH3 domain, a proline-rich domain, and a C-terminal VCA (verprolin-homology and cofilin-like acidic) domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*...
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRK-WWKVRDHQGQEGYVPYNILT 532
Cdd:cd11849   6 YDFKSAEPNTLSFSEGETFLLLERSNAhWWLVTNHSGETGYVPANYVK 53

Src homology 3 domains of the p47phox subunit of NADPH oxidase and similar domains; This family is composed of the tandem SH3 domains of p47phox subunit of NADPH oxidase and Nox Organizing protein 1 (NoxO1), the four SH3 domains of Tks4 (Tyr kinase substrate with four SH3 domains), the five SH3 domains of Tks5, the SH3 domain of obscurin, Myosin-I, and similar domains. Most members of this group also contain Phox homology (PX) domains, except for obscurin and Myosin-I. p47phox and NoxO1 are regulators of the phagocytic NADPH oxidase complex (also called Nox2 or gp91phox) and nonphagocytic NADPH oxidase Nox1, respectively. They play roles in the activation of their respective NADPH oxidase, which catalyzes the transfer of electrons from NADPH to molecular oxygen to form superoxide. Tks proteins are Src substrates and scaffolding proteins that play important roles in the formation of podosomes and invadopodia, the dynamic actin-rich structures that are related to cell migration and cancer cell invasion. Obscurin is a giant muscle protein that plays important roles in the organization and assembly of the myofibril and the sarcoplasmic reticulum. Type I myosins (Myosin-I) are actin-dependent motors in endocytic actin structures and actin patches. They play roles in membrane traffic in endocytic and secretory pathways, cell motility, and mechanosensing. Myosin-I contains an N-terminal actin-activated ATPase, a phospholipid-binding TH1 (tail homology 1) domain, and a C-terminal extension which includes an F-actin-binding TH2 domain, an SH3 domain, and an acidic peptide that participates in activating the Arp2/3complex. The SH3 domain of myosin-I is required for myosin-I-induced actin polymerization. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*....
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLD-DRRKWWKVRDHqGQEGYVPYNILTP 533
Cdd:cd11856   6 ADYEAQGDDEISLQEGEVVEVLEkNDSGWWYVRKG-DKEGWVPASYLEP 53

C-terminal Src homology 3 domain of GRB2-related adaptor protein 2; GRAP2 is also called GADS (GRB2-related adapter downstream of Shc), GrpL, GRB2L, Mona, or GRID (Grb2-related protein with insert domain). It is expressed specifically in the hematopoietic system. It plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. It also has roles in antigen-receptor and tyrosine kinase mediated signaling. GRAP2 is unique from other GRB2-like adaptor proteins in that it can be regulated by caspase cleavage. It contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The C-terminal SH3 domain of GRAP2 binds to different motifs found in substrate peptides including the typical PxxP motif in hematopoietic progenitor kinase 1 (HPK1), the RxxK motif in SLP-76 and HPK1, and the RxxxxK motif in phosphatase-like protein HD-PTP. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*....|....
gi 18874094 481 WVLCNYDFQARNGSELSVKHRDVLEVLD-DRRKWWKVRDHqGQEGYVPYNILTP 533
Cdd:cd11950   1 QVRALYDFEALEDDELGFNSGDVIEVLDsSNPSWWKGRLH-GKLGLFPANYVAP 53

C-terminal (or second) Src homology 3 domain of VAV1 protein; VAV1 is expressed predominantly in the hematopoietic system and it plays an important role in the development and activation of B and T cells. It is activated by tyrosine phosphorylation to function as a guanine nucleotide exchange factor (GEF) for Rho GTPases following cell surface receptor activation, triggering various effects such as cytoskeletal reorganization, transcription regulation, cell cycle progression, and calcium mobilization. It also serves as a scaffold protein and has been shown to interact with Ku70, Socs1, Janus kinase 2, SIAH2, S100B, Abl gene, ZAP-70, SLP76, and Syk, among others. VAV proteins contain several domains that enable their function: N-terminal calponin homology (CH), acidic, RhoGEF (also called Dbl-homologous or DH), Pleckstrin Homology (PH), C1 (zinc finger), SH2, and two SH3 domains. The C-terminal SH3 domain of Vav1 interacts with a wide variety of proteins including cytoskeletal regulators (zyxin), RNA-binding proteins (Sam68), transcriptional regulators, viral proteins, and dynamin 2. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*.
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDR--RKWWKVRDHqGQEGYVPYN 529
Cdd:cd11976   6 YDFCARDRSELSLKEGDIIKILNKKgqQGWWRGEIY-GRVGWFPAN 50

Second or C-terminal Src homology 3 domain of NADPH oxidase (Nox) Organizing protein 1; Nox Organizing protein 1 (NoxO1) is a critical regulator of enzyme kinetics of the nonphagocytic NADPH oxidase Nox1, which catalyzes the transfer of electrons from NADPH to molecular oxygen to form superoxide. Nox1 is expressed in colon, stomach, uterus, prostate, and vascular smooth muscle cells. NoxO1 is involved in targeting activator subunits (such as NoxA1) to Nox1. It is co-localized with Nox1 in the membranes of resting cells and directs the subcellular localization of Nox1. NoxO1 contains an N-terminal Phox homology (PX) domain, tandem SH3 domains (N-SH3 and C-SH3), and a C-terminal proline-rich region (PRR). This model characterizes the second SH3 domain (or C-SH3) of NoxO1. The tandem SH3 domains of NoxO1 interact with the PRR of p22phox, which also complexes with Nox1. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*..
gi 18874094 488 FQARNGSELSVKHRDVLEVLDDR-RKWWKVRdHQGQEGYVPYNILTP 533
Cdd:cd12024   8 YEAQKEDELSVPAGVVVEVLQKSdNGWWLIR-YNGRAGYVPSMYLQP 53

Variant SH3 domain;

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                  ....*....|....*....|....*....|....*....|....*...
gi 18874094   486 YDFQARNGSELSVKHRDVLEVLDDRRK-WWKVRDHqGQEGYVPYNILT 532
Cdd:pfam14604   3 YPYEPKDDDELSLQRGDVITVIEESEDgWWEGINT-GRTGLVPANYVE 49

Src homology 3 domain of Myosins Ie, If, and similar proteins; Myosins Ie (MyoIe) and If (MyoIf) are nonmuscle, unconventional, long tailed, class I myosins containing an N-terminal motor domain and a myosin tail with TH1, TH2, and SH3 domains. MyoIe interacts with the endocytic proteins, dynamin and synaptojanin-1, through its SH3 domain; it may play a role in clathrin-dependent endocytosis. In the kidney, MyoIe is critical for podocyte function and normal glomerular filtration. Mutations in MyoIe is associated with focal segmental glomerulosclerosis, a disease characterized by massive proteinuria and progression to end-stage kidney disease. MyoIf is predominantly expressed in the immune system; it plays a role in immune cell motility and innate immunity. Mutations in MyoIf may be associated with the loss of hearing. The MyoIf gene has also been found to be fused to the MLL (Mixed lineage leukemia) gene in infant acute myeloid leukemias (AML). SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL-DDRRKWWKVRDHqGQEGYVPYN 529
Cdd:cd11827   6 YAYDAQDTDELSFNEGDIIEILkEDPSGWWTGRLR-GKEGLFPGN 49

Src homology 3 domain of Type I fungal Myosins; Type I myosins (myosin-I) are actin-dependent motors in endocytic actin structures and actin patches. They play roles in membrane traffic in endocytic and secretory pathways, cell motility, and mechanosensing. Saccharomyces cerevisiae has two myosins-I, Myo3 and Myo5, which are involved in endocytosis and the polarization of the actin cytoskeleton. Myosin-I contains an N-terminal actin-activated ATPase, a phospholipid-binding TH1 (tail homology 1) domain, and a C-terminal extension which includes an F-actin-binding TH2 domain, an SH3 domain, and an acidic peptide that participates in activating the Arp2/3complex. The SH3 domain of myosin-I is required for myosin-I-induced actin polymerization. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 486 YDFQARNGSELSVKHRDVLEVL-DDRRKWWKVRDHQGQ-EGYVPYNILTP 533
Cdd:cd11858   6 YDFAGSVANELSLKKDDIVYIVqKEDNGWWLAKKLDESkEGWVPAAYLEE 55

C-terminal Src homology 3 domain of Growth factor receptor-bound protein 2 (GRB2) and related proteins; This family includes the adaptor protein GRB2 and related proteins including Drosophila melanogaster Downstream of receptor kinase (DRK), Caenorhabditis elegans Sex muscle abnormal protein 5 (Sem-5), GRB2-related adaptor protein (GRAP), GRAP2, and similar proteins. Family members contain an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. GRB2/Sem-5/DRK is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. GRAP2 plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. GRAP acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. The C-terminal SH3 domains (SH3c) of GRB2 and GRAP2 have been shown to bind to classical PxxP motif ligands, as well as to non-classical motifs. GRB2 SH3c binds Gab2 (Grb2-associated binder 2) through epitopes containing RxxK motifs, while the SH3c of GRAP2 binds to the phosphatase-like protein HD-PTP via a RxxxxK motif. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 18874094 486 YDFQARNGSELSVKHRDVLEVLD-DRRKWWKVRDHqGQEGYVPYNILTP 533
Cdd:cd11805   6 YDFNPQEPGELEFRRGDIITVLDsSDPDWWKGELR-GRVGIFPANYVQP 53

First Src homology 3 domain of the RhoGEF kinase, Kalirin; Kalirin, also called Duo, Duet, or TRAD, is a large neuronal dual Rho guanine nucleotide exchange factor (RhoGEF) that activates Rac1, RhoA, and RhoG using two RhoGEF domains. Kalirin exists in many isoforms generated by alternative splicing and the use of multiple promoters; the major isoforms are kalirin-7, -9, and -12, which differ at their C-terminal ends. Kalirin-12, the longest isoform, contains an N-terminal Sec14p domain, spectrin-like repeats, two RhoGEF domains, two SH3 domains, as well as Ig, FNIII, and kinase domains at the C-terminal end. Kalirin-7 contains only a single RhoGEF domain and does not contain an SH3 domain. Kalirin, through its many isoforms, interacts with many different proteins and is able to localize to different locations within the cell. It influences neurite initiation, axon growth, dendritic morphogenesis, vesicle trafficking, neuronal maintenance, and neurodegeneration. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 18874094 481 WVLcnYDFQARNGSELSVKHR---DVLEVLDDRRKWWKVR-----DHQGQEGYVPYNILTP 533
Cdd:cd11852   4 VVI--EDFEATSSQELTVSKGqtvEVLERPSSRPDWCLVRtleqdNSPPQEGLVPSSILCI 62

Src Homology 3 domain of metazoan osteoclast stimulating factor 1; OSTF1, also named OSF or SH3P2, is a signaling protein containing SH3 and ankyrin-repeat domains. It acts through a Src-related pathway to enhance the formation of osteoclasts and bone resorption. It also acts as a negative regulator of cell motility. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRK-WWKVRdHQGQEGYVPYNILTP 533
Cdd:cd11772   6 YDYEAQHPDELSFEEGDLLYISDKSDPnWWKAT-CGGKTGLIPSNYVEE 53

Src homology 3 domain of Src Protein Tyrosine Kinase; Src (or c-Src) is a cytoplasmic (or non-receptor) PTK and is the vertebrate homolog of the oncogenic protein (v-Src) from Rous sarcoma virus. Together with other Src subfamily proteins, it is involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. Src also play a role in regulating cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Elevated levels of Src kinase activity have been reported in a variety of human cancers. Several inhibitors of Src have been developed as anti-cancer drugs. Src is also implicated in acute inflammatory responses and osteoclast function. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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                ....*....|....*....|....*....|....*....|....*....|
gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRR-KWWKVRD-HQGQEGYVPYNILTP 533
Cdd:cd12008   6 YDYESRTETDLSFKKGERLQIVNNTEgDWWLAHSlTTGQTGYIPSNYVAP 55

C-terminal Src homology 3 domain of GRB2-related adaptor protein; GRAP is a GRB-2 like adaptor protein that is highly expressed in lymphoid tissues. It acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. It has been identified as a regulator of TGFbeta signaling in diabetic kidney tubules and may have a role in the pathogenesis of the disease. GRAP contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The C-terminal SH3 domains (SH3c) of the related proteins, GRB2 and GRAP2, have been shown to bind to classical PxxP motif ligands, as well as to non-classical motifs. GRB2 SH3c binds Gab2 (Grb2-associated binder 2) through epitopes containing RxxK motifs, while the SH3c of GRAP2 binds to the phosphatase-like protein HD-PTP via a RxxxxK motif. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 18874094 481 WVLCNYDFQARNGSELSVKHRDVLEVLD-DRRKWWKVRDHqGQEGYVPYNILTP 533
Cdd:cd11951   1 FVQAQYDFSAEDPSQLSFRRGDIIEVLDcPDPNWWRGRIS-GRVGFFPRNYVHP 53

Src homology 3 domain of Srms Protein Tyrosine Kinase; Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites (Srms) is a cytoplasmic (or non-receptor) PTK with limited homology to Src kinases. Src kinases in general contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr; they are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Srms lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 18874094 486 YDFQARNGSELSVKHRDVLEVLDDRRKWWKVRDHQGQ--EGYVPYN 529
Cdd:cd11846   6 YDFTARSTHELSVEQGDKLCVIEEEGDYIFARKLTGNpeSGLVPAS 51