Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436  513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKG 592
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGKYTCVATNSAG 80

                          90
                  ....*....|
gi 240849436  593 SAASTCILTI 602
Cdd:pfam07679  81 EAEASAELTV 90

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436  513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKG 592
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGKYTCVATNSAG 80

                          90
                  ....*....|
gi 240849436  593 SAASTCILTI 602
Cdd:pfam07679  81 EAEASAELTV 90

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436   520 RNTSVVDSEPVRFTVKVTGEPKPEITWWFEG-EILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGSAASTC 598
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGgKLLAESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGT 81

                   ....
gi 240849436   599 ILTI 602
Cdd:smart00410  82 TLTV 85

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436  513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKG 592
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGKYTCVATNSAG 80

                          90
                  ....*....|
gi 240849436  593 SAASTCILTI 602
Cdd:pfam07679  81 EAEASAELTV 90

Second Ig-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk and similar proteins. Titin is a key component in the assembly and functioning of vertebrate striated muscles. By providing connections at the level of individual microfilaments, it contributes to the fine balance of forces between the two halves of the sarcomere. 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 titin Z1z2 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 240849436 512 APWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNK 591
Cdd:cd20972    1 PPQFIQKLRSQEVAEGSKVRLECRVTGNPTPVVRWFCEGKELQNSPDIQIHQEGDLHSLIIAEAFEEDTGRYSCLATNSV 80

                 ....*.
gi 240849436 592 GSAAST 597
Cdd:cd20972   81 GSDTTS 86

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 240849436  518 PLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVN 589
Cdd:pfam13927   7 SPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 78

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 240849436 530 VRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGSAAST 597
Cdd:cd00096    1 VTLTCSASGNPPPTITWYKNGKPLPPSSRDSRRSELGNGTLTISNVTLEDSGTYTCVASNSAGGSASA 68

First C-terminal immunoglobulin (Ig)-like domain of palladin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of palladin. Palladin belongs to the palladin-myotilin-myopalladin family. Proteins belonging to this family contain multiple Ig-like domains and function as scaffolds, modulating actin cytoskeleton. Palladin binds to alpha-actinin ezrin, vasodilator-stimulated phosphoprotein VASP, SPIN90 (also known as DIP or mDia interacting protein), and Src. Palladin also binds F-actin directly, via its Ig3 domain. Palladin is expressed as several alternatively spliced isoforms, having various combinations of Ig-like domains, in a cell-type-specific manner. It has been suggested that palladin's different Ig-like domains may be specialized for distinct functions. 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 240849436 513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIER--GETYCLYLPETFPEDGGEYMCKAVNN 590
Cdd:cd05893    1 PFFEMKLKHYKIFEGMPVTFTCRVAGNPKPKIYWFKDGKQISPKSDHYTIQRdlDGTCSLHTTASTLDDDGNYTIMAANP 80

                         90
                 ....*....|..
gi 240849436 591 KGSAASTCILTI 602
Cdd:cd05893   81 QGRISCTGRLMV 92

Immunoglobulin (Ig)-like domain of myotilin, palladin, and myopalladin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain in myotilin, palladin, and myopalladin. Myotilin, palladin, and myopalladin function as scaffolds that regulate actin organization. Myotilin and myopalladin are most abundant in skeletal and cardiac muscle; palladin is ubiquitously expressed in the organs of developing vertebrates and plays a key role in cellular morphogenesis. The three family members each interact with specific molecular partners with all three binding to alpha-actinin; In addition, palladin also binds to vasodilator-stimulated phosphoprotein (VASP) and ezrin, myotilin binds to filamin and actin, and myopalladin also binds to nebulin and cardiac ankyrin repeat protein (CARP). 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 240849436 513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQ-DGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNK 591
Cdd:cd05744    1 PHFLQAPGDLEVQEGRLCRFDCKVSGLPTPDLFWQLNGKPVRpDSAHKMLVRENGRHSLIIEPVTKRDAGIYTCIARNRA 80

                         90
                 ....*....|.
gi 240849436 592 GSAASTCILTI 602
Cdd:cd05744   81 GENSFNAELVV 91

First Ig-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk and similar proteins; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin (Ig)-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk and similar proteins. Titin is a key component in the assembly and functioning of vertebrate striated muscles. By providing connections at the level of individual microfilaments, it contributes to the fine balance of forces between the two halves of the sarcomere. 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 titin Z1z2 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 240849436 513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEI--LQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNN 590
Cdd:cd20974    1 PVFTQPLQSVVVLEGSTATFEAHVSGKPVPEVSWFRDGQVisTSTLPGVQISFSDGRAKLSIPAVTKANSGRYSLTATNG 80

                         90
                 ....*....|..
gi 240849436 591 KGSAASTCILTI 602
Cdd:cd20974   81 SGQATSTAELLV 92

Immunoglobulin (Ig)-like domain of titin and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain found in titin-like proteins and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is a giant protein; depending on isoform composition, it ranges from 2970 to 3700 kDa, and is of a length that spans half a sarcomere. Titin largely consists of multiple repeats of Ig-like and fibronectin type 3 (FN-III)-like domains. Titin connects the ends of myosin thick filaments to Z disks and extends along the thick filament to the H zone. It appears to function similarly to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. Within the sarcomere, titin is also attached to or is associated with myosin binding protein C (MyBP-C). MyBP-C appears to contribute to the generation of passive tension by titin and like titin has repeated Ig-like and FN-III domains. Also included in this group are worm twitchin and insect projectin, thick filament proteins of invertebrate muscle which also have repeated Ig-like and FN-III domains.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 240849436 528 EPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQyIERGETY-CLYLPETFPEDGGEYMCKAVNNKGSAASTCILTI 602
Cdd:cd05748    8 ESLRLDIPIKGRPTPTVTWSKDGQPLKETGRVQ-IETTASStSLVIKNAKRSDSGKYTLTLKNSAGEKSATINVKV 82

C-terminal immunoglobulin-like domain of the myosin-associated giant protein kinase Twitchin, and similar domains; member of the I-set IgSF domains; The members here are composed of the C-terminal immunoglobulin-like domain of the myosin-associated giant protein kinase Twitchin and similar proteins, including Caenorhabditis elegans and Aplysia californica Twitchin, Drosophila melanogaster Projectin, and similar proteins. These are very large muscle proteins containing multiple immunoglobulin (Ig)-like and fibronectin type III (FN3) domains and a single kinase domain near the C-terminus. In humans these proteins are called Titin. 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. The Ig-like domain of the Twitchin is a member of the I-set 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. 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.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 522 TSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGSAASTCILT 601
Cdd:cd20949    9 TTVKEGQSATILCEVKGEPQPNVTWHFNGQPISASVADMSKYRILADGLLINKVTQDDTGEYTCRAYQVNSIASDMQERT 88

                 .
gi 240849436 602 I 602
Cdd:cd20949   89 V 89

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor_like-1(FGFRL1); member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 is comprised of a signal peptide, three extracellular Ig-like modules, a transmembrane segment, and a short intracellular domain. FGFRL1 is expressed preferentially in skeletal tissues. Similar to FGF receptors, the expressed protein interacts specifically with heparin and with FGF2. FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 513 PWFKKPLRNTSVVDSEP----VRFTVKVTGEPKPEITWWFEGEILQDGEDYQyiERGETYCLYLPETFPEDGGEYMCKAV 588
Cdd:cd05856    1 PRFTQPAKMRRRVIARPvgssVRLKCVASGNPRPDITWLKDNKPLTPPEIGE--NKKKKWTLSLKNLKPEDSGKYTCHVS 78

                 ....*....
gi 240849436 589 NNKGSAAST 597
Cdd:cd05856   79 NRAGEINAT 87

Immunoglobulin (Ig)-like domain of human titin C terminus and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain from the C-terminus of human titin x and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is gigantic; depending on isoform composition it ranges from 2970 to 3700 kDa, and is of a length that spans half a sarcomere. Titin largely consists of multiple repeats of Ig-like and fibronectin type 3 (FN-III)-like domains. Titin connects the ends of myosin thick filaments to Z disks and extends along the thick filament to the H zone and appears to function similar to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. 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 240849436 517 KPlRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGSAAS 596
Cdd:cd05747    9 KP-RSLTVSEGESARFSCDVDGEPAPTVTWMREGQIIVSSQRHQITSTEYKSTFEISKVQMSDEGNYTVVVENSEGKQEA 87

                 ....*
gi 240849436 597 TCILT 601
Cdd:cd05747   88 QFTLT 92

C-terminal immunoglobulin (Ig)-like domain of myotilin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of myotilin. Mytolin belongs to the palladin-myotilin-myopalladin family. Proteins belonging to the latter family contain multiple Ig-like domains and function as scaffolds, modulating the actin cytoskeleton. Myotilin is most abundant in skeletal and cardiac muscle and is involved in maintaining sarcomere integrity. It binds to alpha-actinin, filamin, and actin. Mutations in myotilin lead to muscle disorders. 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 240849436 513 PWFKKPLRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGED----YQ----YIergetyCLYLPETFPEDGGEYM 584
Cdd:cd05892    1 PMFIQKPQNKKVLEGDPVRLECQISAIPPPQIFWKKNNEMLQYNTDrislYQdncgRI------CLLIQNANKKDAGWYT 74

                         90
                 ....*....|...
gi 240849436 585 CKAVNNKGSAAST 597
Cdd:cd05892   75 VSAVNEAGVVSCN 87

Immunoglobulin (Ig)-like domain of the human basement membrane heparan sulfate proteoglycan perlecan and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain of the human basement membrane heparan sulfate proteoglycan perlecan, also known as HSPG2, and similar proteins. Perlecan consists of five domains: domain I has three putative heparan sulfate attachment sites, domain II has four LDL receptor-like repeats, and one Ig-like repeat, domain III resembles the short arm of laminin chains, domain IV has multiple Ig-like repeats (21 repeats in human perlecan), and domain V resembles the globular G domain of the laminin A chain and internal repeats of EGF. Perlecan may participate in a variety of biological functions including cell binding, LDL-metabolism, basement membrane assembly and selective permeability, calcium binding, and growth- and neurite-promoting activities.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 528 EPVRFTVKVTGEPKPEITW---WfeGEILQDGEDYQYIERGeTYCLYLPETFPEDGGEYMCKAVNNKGS--AASTCILTI 602
Cdd:cd05743    2 ETVEFTCVATGVPTPIINWrlnW--GHVPDSARVSITSEGG-YGTLTIRDVKESDQGAYTCEAINTRGMvfGIPDGILTV 78

Fourth 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 fourth 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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 240849436 537 TGEPKPEITWWFEGEILQDGEDYQY----IERGET--YcLYLPETFPEDGGEYMCKAVNNKGSA 594
Cdd:cd20956   26 SGNPLPQITWTLDGFPIPESPRFRVgdyvTSDGDVvsY-VNISSVRVEDGGEYTCTATNDVGSV 88

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three IG-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 240849436 530 VRFTVKVTGEPKPEITWWFEG-EILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGSAAST 597
Cdd:cd05857   22 VKFRCPAAGNPTPTMRWLKNGkEFKQEHRIGGYKVRNQHWSLIMESVVPSDKGNYTCVVENEYGSINHT 90

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 240849436 521 NTSVVDSEPVRFTVKVTGePKPEITWWFEGEILQDGEDYQYIERGETycLYLPETFPEDGGEYMCKAVN 589
Cdd:cd05740    9 SNPVEDKDAVTLTCEPET-QNTSYLWWFNGQSLPVTPRLTLSNGNRT--LTLLNVTREDAGAYQCEISN 74

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM); The members here are composed of the third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains, five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 240849436 538 GEPKPEITWW-FEGEILQDGEDYQYIERgetyCLYLPETFPEDGGEYMCKAVNNKGSAASTCILTIE 603
Cdd:cd05876   21 GLPTPTVKWLrPSGPLPPDRVKYQNHNK----TLQLLNVGESDDGEYVCLAENSLGSARHAYYVTVE 83

Third immunoglobulin-like domain of the human WFIKKN (WAP, follistatin, immunoglobulin, Kunitz and NTR domain-containing protein), and similar domains; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin-like domain of the human WFIKKN (WAP, follistatin, immunoglobulin, Kunitz and NTR domain-containing protein) and similar proteins. WFIKKN is a secreted protein that consists of multiple types of protease inhibitory modules, including two tandem Kunitz-type protease inhibitor-domains. The Ig superfamily is a heterogenous group of proteins built on a common fold comprised of a sandwich of two beta sheets. Members of the Ig superfamily are components of immunoglobulin, neuroglia, cell surface glycoproteins, such as T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, such as 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. 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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 240849436 523 SVVDSEPVRFTVKVTGEPKPEITW--WFEGE---ILQDGEDYQYIERGETYCLYLPETFPEDGGEYMCKAVNNKGS 593
Cdd:cd05765   11 TVKVGETASFHCDVTGRPQPEITWekQVPGKenlIMRPNHVRGNVVVTNIGQLVIYNAQPQDAGLYTCTARNSGGL 86

Second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second 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 the 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, and 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, 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 Slit-2 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.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 538 GEPKPEITWWFEG-EILQDGEDYQYIERGEtycLYLPETFPEDGGEYMCKAVNNKGSAAS 596
Cdd:cd05724   24 GHPEPTVSWRKDGqPLNLDNERVRIVDDGN---LLIAEARKSDEGTYKCVATNMVGERES 80

Fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related); The members here are composed of the fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related). These proteins belong to the L1 subfamily of cell adhesion molecules (CAMs) and are comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. These molecules are primarily expressed in the nervous system. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 514 WFKKPlRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQD-GEDYQYIERGETycLYLPETFPEDGGEYMCKAVNNKG 592
Cdd:cd04978    2 WIIEP-PSLVLSPGETGELICEAEGNPQPTITWRLNGVPIEPaPEDMRRTVDGRT--LIFSNLQPNDTAVYQCNASNVHG 78

First immunoglobulin (Ig) domain of contactin; member of the I-set of (Ig) superfamily domains; The members here are composed of the first 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. This group belongs to the I-set of IgSF domains.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 240849436 526 DSEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGETYCLYLPETfPEDGGEYMCKAVNNKGSAAST 597
Cdd:cd04967   18 DEKKVALNCRARANPVPSYRWLMNGTEIDLESDYRYSLVDGTLVISNPSK-AKDAGHYQCLATNTVGSVLSR 88

Third immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the Constant 2 (C2)-set of IgSF domains; The members here are composed of the third 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. 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. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C, and C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 240849436 521 NTSVVD-SEPVRFTVKVTGEPKPEITWWFEGEILQDGEDYQYIERGEtycLYLPETFPEDGGEYMCKAVNNKGSAASTCI 599
Cdd:cd20957    9 PVQTVDfGRTAVFNCSVTGNPIHTVLWMKDGKPLGHSSRVQILSEDV---LVIPSVKREDKGMYQCFVRNDGDSAQATAE 85

                 ...
gi 240849436 600 LTI 602
Cdd:cd20957   86 LKL 88

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. 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, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -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, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -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 is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 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. 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

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gi 240849436 518 PLRNTSVVDSEPVrFTVKVTGEPKPEITWWFEG-EILQDGEDYQYIERGETYCLYLPEtfpEDGGEYMCKAVNNKGSAAS 596
Cdd:cd20952    6 PQNQTVAVGGTVV-LNCQATGEPVPTISWLKDGvPLLGKDERITTLENGSLQIKGAEK---SDTGEYTCVALNLSGEATW 81

                 ....*.
gi 240849436 597 TCILTI 602
Cdd:cd20952   82 SAVLDV 87

Immunoglobulin (Ig)-like I-set domain of Neural Cell Adhesion Molecule 1 (NCAM-1) and similar proteins; The members here are composed of the fourth immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions), through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain. Also included in this group is NCAM-2 (also known as OCAM/mamFas II and RNCAM) NCAM-2 is differentially expressed in the developing and mature olfactory epithelium (OE). One of the unique features of I-set domains is the lack of a C" strand. The structures of this group show that the Ig domain lacks this strand and thus is a member of the I-set of Ig domains.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 240849436 519 LRNTSVVDSEPVRFTVKVTGEPKPEITWWFEGEILQDGE---DYQYIERGE--TYCLYLPETFPEDGGEYMCKAVNNKG 592
Cdd:cd05732    8 LENQTAVELEQITLTCEAEGDPIPEITWRRATRGISFEEgdlDGRIVVRGHarVSSLTLKDVQLTDAGRYDCEASNRIG 86