First immunoglobulin (Ig)-like domain of carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM); The members here are composed of the immunoglobulin (Ig)-like domain 1 in carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) proteins. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions: it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two (D1, D4) or four (D1-D4) Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 278 LIIDPMPRYAAEGESILLRVLNLPEDFQVFCWYKGALIFQIFKIAEYSRARNSITKGPAQSRTERVYTNGSLLLQDVTEK 357
Cdd:cd05774     1 LTIELVPPQVAEGENVLLLVHNLPENLLAYAWYKGKTVSPNFLIASYIISTNSSTPGPAYSGRETIYPNGSLLIQNVTQK 80

                          90       100
                  ....*....|....*....|....*
gi 1720422726 358 DTGLYTLQTIDRNFKIEKAHVQIQV 382
Cdd:cd05774    81 DTGFYTLQTITADLQTEQASVHLQV 105

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 388 QPFMRV-TDSTVRVQSSVVFTCFSDNTGVSIHWLFNNQSLQLTERITLSPSKCQLRINPVRKEDGGEYQCEVFNLASSKS 466
Cdd:cd05740     1 KPFISSnNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANR 80

                  ....*....
gi 1720422726 467 SLPVSLAVM 475
Cdd:cd05740    81 SDPVTLDVI 89

First immunoglobulin (Ig)-like domain of carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM); The members here are composed of the immunoglobulin (Ig)-like domain 1 in carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) proteins. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions: it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two (D1, D4) or four (D1-D4) Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 278 LIIDPMPRYAAEGESILLRVLNLPEDFQVFCWYKGALIFQIFKIAEYSRARNSITKGPAQSRTERVYTNGSLLLQDVTEK 357
Cdd:cd05774     1 LTIELVPPQVAEGENVLLLVHNLPENLLAYAWYKGKTVSPNFLIASYIISTNSSTPGPAYSGRETIYPNGSLLIQNVTQK 80

                          90       100
                  ....*....|....*....|....*
gi 1720422726 358 DTGLYTLQTIDRNFKIEKAHVQIQV 382
Cdd:cd05774    81 DTGFYTLQTITADLQTEQASVHLQV 105

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 388 QPFMRV-TDSTVRVQSSVVFTCFSDNTGVSIHWLFNNQSLQLTERITLSPSKCQLRINPVRKEDGGEYQCEVFNLASSKS 466
Cdd:cd05740     1 KPFISSnNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANR 80

                  ....*....
gi 1720422726 467 SLPVSLAVM 475
Cdd:cd05740    81 SDPVTLDVI 89

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 280 IDPMPRYAAEGESILLRVLNLP---EDFQVFCWYKGALIFQI-FKIAEYSRARN-SITKGPAQSRTERVYTNGSLLLQDV 354
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSsmsEASTSVYWYRQPPGKGPtFLIAYYSNGSEeGVKKGRFSGRGDPSNGDGSLTIQNL 80

                          90       100
                  ....*....|....*....|....*...
gi 1720422726 355 TEKDTGLYTLQTIDRNFKIEKAHVQIQV 382
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTV 108

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1720422726 397 TVRVQSSVVFTCFS--DNTGVSIHWLFNNQSLQLTERITLSP---SKCQLRINPVRKEDGGEYQCEVFNLASSKSS 467
Cdd:pfam00047   7 TVLEGDSATLTCSAstGSPGPDVTWSKEGGTLIESLKVKHDNgrtTQSSLLISNVTKEDAGTYTCVVNNPGGSATL 82

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726   51 VVEGENVLL--RVDNLPENLITlaWYRGLRKIVVYTLNTKVSVMGqmysgreivsSNGSLWIHNVTRKDTGLYTLRTVNR 128
Cdd:smart00410   6 VKEGESVTLscEASGSPPPEVT--WYKQGGKLLAESGRFSVSRSG----------STSTLTISNVTPEDSGTYTCAATNS 73

                           90
                   ....*....|....
gi 1720422726  129 RGEIvsTSFTFLYV 142
Cdd:smart00410  74 SGSA--SSGTTLTV 85

First immunoglobulin (Ig)-like domain of carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM); The members here are composed of the immunoglobulin (Ig)-like domain 1 in carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) proteins. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions: it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two (D1, D4) or four (D1-D4) Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 278 LIIDPMPRYAAEGESILLRVLNLPEDFQVFCWYKGALIFQIFKIAEYSRARNSITKGPAQSRTERVYTNGSLLLQDVTEK 357
Cdd:cd05774     1 LTIELVPPQVAEGENVLLLVHNLPENLLAYAWYKGKTVSPNFLIASYIISTNSSTPGPAYSGRETIYPNGSLLIQNVTQK 80

                          90       100
                  ....*....|....*....|....*
gi 1720422726 358 DTGLYTLQTIDRNFKIEKAHVQIQV 382
Cdd:cd05774    81 DTGFYTLQTITADLQTEQASVHLQV 105

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 388 QPFMRV-TDSTVRVQSSVVFTCFSDNTGVSIHWLFNNQSLQLTERITLSPSKCQLRINPVRKEDGGEYQCEVFNLASSKS 466
Cdd:cd05740     1 KPFISSnNSNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANR 80

                  ....*....
gi 1720422726 467 SLPVSLAVM 475
Cdd:cd05740    81 SDPVTLDVI 89

Immunoglobulin (Ig)-like domain of carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain in carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) and related domains. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions: it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two (D1, D4) or four (D1-D4) Ig-like domains on the cell surface. This family corresponds to the D1 Ig-like domain. Also belonging to this group is the N-terminal immunoglobulin (Ig)-like domain of the signaling lymphocyte activation molecule (SLAM) family, CD84-like family. The SLAM family is a group of immune-cell specific receptors that can regulate both adaptive and innate immune responses. SLAM family proteins are organized as an extracellular domain with having two or four Ig-like domains, a single transmembrane segment, and a cytoplasmic region having Tyr-based motifs. The extracellular domain is organized as a membrane-distal Ig variable (IgV) domain that is responsible for ligand recognition and a membrane-proximal truncated Ig constant-2 (IgC2) domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 286 YAAEGESILLRVLNLPEDFQVFCWYKGALIFQIFKIAEYSRARNSITKGPAQSRTERVYTNGSLLLQDVTEKDTGLYTLQ 365
Cdd:cd05741     6 YGAEGKNVLLLVPNLQTPLKSVSWYKGKQVSRNDEIAEYENSSDEFRAGSAFSGREYIYTNGSLLIQNITLSDTGFYTLE 85

                          90
                  ....*....|....*..
gi 1720422726 366 TIDRNFKIEKAHVQIQV 382
Cdd:cd05741    86 STNIGGKTESATFQLHV 102

N-terminal immunoglobulin (Ig)-like domain of T-cell surface antigen CD2, and similar domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain (or domain 1) of T-cell surface antigen Clusters of Differentiation (CD) 2 and similar proteins. CD2 is a T-cell specific surface glycoprotein and is critically important for mediating adhesion between T cells and antigen-presenting cells or between cytolytic T cells and target cells. CD2 is located on chromosome 1 at 1p13 in humans and on chromosome 3 in mice. CD2 contains an extracellular domain with two or Ig-like domains, a single transmembrane segment, and a cytoplasmic region rich in proline and basic residues.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726  52 VEGENVLLRVDNLPENLITLAWYRGLRKIVVYTLNTKVSVMGQmYSGR-EIVSSNGSLWIHNVTRKDTGLYTLRTVNRRG 130
Cdd:cd05775     8 ALGGNVTLTISSLQDDIDEIKWKKTKDKIVEWENNIGPTYFGS-FKDRvLLDKESGSLTIKNLTKEDSGTYELEITSTNG 86

                          90
                  ....*....|...
gi 1720422726 131 EIVSTSFTfLYVY 143
Cdd:cd05775    87 KVLSSKFT-LEVL 98

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 280 IDPMPRYAAEGESILLRVLNLP---EDFQVFCWYKGALIFQI-FKIAEYSRARN-SITKGPAQSRTERVYTNGSLLLQDV 354
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSsmsEASTSVYWYRQPPGKGPtFLIAYYSNGSEeGVKKGRFSGRGDPSNGDGSLTIQNL 80

                          90       100
                  ....*....|....*....|....*...
gi 1720422726 355 TEKDTGLYTLQTIDRNFKIEKAHVQIQV 382
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTV 108

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1720422726 404 VVFTC-FSDNTGVSIHWLFNNQSLQLT--ERITLSPSKCQLRINPVRKEDGGEYQCEVFNLASSKSS 467
Cdd:cd00096     1 VTLTCsASGNPPPTITWYKNGKPLPPSsrDSRRSELGNGTLTISNVTLEDSGTYTCVASNSAGGSAS 67

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1720422726 397 TVRVQSSVVFTCFS--DNTGVSIHWLFNNQSLQLTERITLSP---SKCQLRINPVRKEDGGEYQCEVFNLASSKSS 467
Cdd:pfam00047   7 TVLEGDSATLTCSAstGSPGPDVTWSKEGGTLIESLKVKHDNgrtTQSSLLISNVTKEDAGTYTCVVNNPGGSATL 82

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 394 TDSTVRVQSSVVFTCFSD-NTGVSIHWLFNNQSL--QLTERITLSPSKCQLRINPVRKEDGGEYQCEVFN 460
Cdd:pfam13927   9 SSVTVREGETVTLTCEATgSPPPTITWYKNGEPIssGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 78

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726   51 VVEGENVLL--RVDNLPENLITlaWYRGLRKIVVYTLNTKVSVMGqmysgreivsSNGSLWIHNVTRKDTGLYTLRTVNR 128
Cdd:smart00410   6 VKEGESVTLscEASGSPPPEVT--WYKQGGKLLAESGRFSVSRSG----------STSTLTISNVTPEDSGTYTCAATNS 73

                           90
                   ....*....|....
gi 1720422726  129 RGEIvsTSFTFLYV 142
Cdd:smart00410  74 SGSA--SSGTTLTV 85

Fourth immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; Members here are composed the fourth immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, Robo3), and three mammalian Slit homologs (Slit-1, Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, and Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 386 VTQPfmrvTDSTVRVQSSVVFTCFSD-NTGVSIHW--------LFNNQSLQLTERITLSPSKcQLRINPVRKEDGGEYQC 456
Cdd:cd05726     3 VVKP----RDQVVALGRTVTFQCETKgNPQPAIFWqkegsqnlLFPYQPPQPSSRFSVSPTG-DLTITNVQRSDVGYYIC 77

                  ....*...
gi 1720422726 457 EVFNLASS 464
Cdd:cd05726    78 QALNVAGS 85

IL-beta-binding protein; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 331 ITKGPAQSRTERV--YTNGSLLLQDVTEKDTGLYT--LQTI--DRNFKIEKAhVQIQVNKPVTQPFMRVTDSTV-RVQSS 403
Cdd:PHA02785  159 IWSGHRRLRNKRLkqRTPGIITIEDVRKNDAGYYTcvLKYIygDKTYNVTRI-VKLEVRDRIIPPTMQLPEGVVtSIGSN 237

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 404 VVFTCFSD----NTGVSIHWLFNNQ-----------SLQLTERITLSPSK----CQLRINPVRKEDGGEYQCEVFNLASS 464
Cdd:PHA02785  238 LTIACRVSlrppTTDADVFWISNGMyyeeddedgdgRISVANKIYTTDKRrvitSRLNINPVKEEDATTFTCMAFTIPSI 317

                  ....*...
gi 1720422726 465 KSSLPVSL 472
Cdd:PHA02785  318 SKTVTISI 325

agrin-responsive second immunoglobulin-like domains (Ig2) of the Muscle-specific kinase (MuSK) ectodomain; a member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin-like (Ig) domains of the Muscle-specific kinase (MuSK) ectodomain. MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 394 TDSTVRVQSSVVFTCFS-DNTGVSIHWLFNNQSLQLTERITLSPSKcQLRINPVRKEDGGEYQCEVFNLASSKSSLPVSL 472
Cdd:cd20968     7 TNVTIIEGLKAVLPCTTmGNPKPSVSWIKGDDLIKENNRIAVLESG-SLRIHNVQKEDAGQYRCVAKNSLGIAYSKPVTI 85

                  ..
gi 1720422726 473 AV 474
Cdd:cd20968    86 EV 87

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1720422726 394 TDSTVRVQSSVVFTCfsDNTGV---SIHWLFNNQSLQ-LTERITLSpsKCQLRINPVRKEDGGEYQCEVFN 460
Cdd:cd20978     9 KNVVVKGGQDVTLPC--QVTGVpqpKITWLHNGKPLQgPMERATVE--DGTLTIINVQPEDTGYYGCVATN 75

Fifth immunoglobulin (Ig) domain of contactin; The members here are composed of the fifth immunoglobulin (Ig) domain of contactins. Contactins are neural cell adhesion molecules and are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. The first four Ig domains form the intermolecular binding fragment, which arranges as a compact U-shaped module via contacts between Ig domains 1 and 4, and between Ig domains 2 and 3. Contactin-2 (TAG-1, axonin-1) may play a part in the neuronal processes of neurite outgrowth, axon guidance and fasciculation, and neuronal migration. This group also includes contactin-1 and contactin-5. The different contactins show different expression patterns in the central nervous system. During development and in adulthood, contactin-2 is transiently expressed in subsets of central and peripheral neurons. Contactin-5 is expressed specifically in the rat postnatal nervous system, peaking at about 3 weeks postnatal, and a lack of contactin-5 (NB-2) results in an impairment of neuronal activity in the rat auditory system. Contactin-5 is highly expressed in the adult human brain in the occipital lobe and in the amygdala. Contactin-1 is differentially expressed in tumor tissues and may, through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma.

                          10        20        30
                  ....*....|....*....|....*....|....*....
gi 1720422726  97 SGREIVSSNGSLWIHNVTRKDTGLYTLRTVNRRGEIVST 135
Cdd:cd04969    46 SSRICILPDGSLKIKNVTKSDEGKYTCFAVNFFGKANST 84

Fifth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726  51 VVEGENVLLR--VDNLPENLITlaWYRGLRKIVVytlntkvsvmgqmySGREIVSSNGSLWIHNVTRK-DTGLYTLRTVN 127
Cdd:cd20958    12 AVAGQTLRLHcpVAGYPISSIT--WEKDGRRLPL--------------NHRQRVFPNGTLVIENVQRSsDEGEYTCTARN 75

                          90
                  ....*....|
gi 1720422726 128 RRGEIVSTSF 137
Cdd:cd20958    76 QQGQSASRSV 85

N-terminal immunoglobulin (Ig)-like domain of T-cell surface antigen CD2, and similar domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain (or domain 1) of T-cell surface antigen Clusters of Differentiation (CD) 2 and similar proteins. CD2 is a T-cell specific surface glycoprotein and is critically important for mediating adhesion between T cells and antigen-presenting cells or between cytolytic T cells and target cells. CD2 is located on chromosome 1 at 1p13 in humans and on chromosome 3 in mice. CD2 contains an extracellular domain with two or Ig-like domains, a single transmembrane segment, and a cytoplasmic region rich in proline and basic residues.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1720422726 168 AEGGSVLLRVHNLQDKLRGLSWYKGAHVSRNLEIARQIIAKNSSvpgpahSGRETV-YSNGSLLLQNVTRNDTGFYTLQT 246
Cdd:cd05775     8 ALGGNVTLTISSLQDDIDEIKWKKTKDKIVEWENNIGPTYFGSF------KDRVLLdKESGSLTIKNLTKEDSGTYELEI 81

                  ....*.
gi 1720422726 247 LSRHRK 252
Cdd:cd05775    82 TSTNGK 87