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        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228  38 GGSIILQCHL-SSTTAQVTQVNWEQQD----QLLAICNADLGWHISPSFKDRV---APGPGL---GLTLQSLTVNDTGEY 106
Cdd:cd05718   14 GGSVTLPCSLtSPGTTKITQVTWMKIGagssQNVAVFHPQYGPSVPNPYAERVeflAARLGLrnaTLRIRNLRVEDEGNY 93

                         90       100
                 ....*....|....*....|
gi 256600228 107 FCIYHTYPDGTYTGRIFLEV 126
Cdd:cd05718   94 ICEFATFPQGNRQGTTWLRV 113

First immunoglobulin variable (IgV) domain of poliovirus receptor (PVR, also known as CD155 and necl-5), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (necl-5)). Poliovirus (PV) binds to its cellular receptor (PVR/CD155) to initiate infection. CD155 is a membrane-anchored, single-span glycoprotein; its extracellular region has three Ig-like domains. There are four different isotypes of CD155 (referred to as alpha, beta, gamma, and delta), that result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted; CD155-alpha and CD155-delta are membrane-bound and function as PV receptors. The virus recognition site is contained in the amino-terminal domain, D1. Having the virus attachment site on the receptor distal from the plasma membrane may be important for successful initiation of infection of cells by the virus. CD155 binds in the poliovirus "canyon" with a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the first Ig-like domain of nectin-1 (also known as poliovirus receptor related protein(PVRL)1; CD111), nectin-3 (also known as PVRL 3), nectin-4 (also known as PVRL4; LNIR receptor)and DNAX accessory molecule 1 (DNAM-1; CD226).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228  38 GGSIILQCHL-SSTTAQVTQVNWEQQD----QLLAICNADLGWHISPSFKDRV---APGPGL---GLTLQSLTVNDTGEY 106
Cdd:cd05718   14 GGSVTLPCSLtSPGTTKITQVTWMKIGagssQNVAVFHPQYGPSVPNPYAERVeflAARLGLrnaTLRIRNLRVEDEGNY 93

                         90       100
                 ....*....|....*....|
gi 256600228 107 FCIYHTYPDGTYTGRIFLEV 126
Cdd:cd05718   94 ICEFATFPQGNRQGTTWLRV 113

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 256600228    40 SIILQCHLSSTTAQVTQVNWEQQDQ-----LLAICNADLGWHISPSFKDRVA----PGPGLG-LTLQSLTVNDTGEYFC 108
Cdd:smart00406   1 SVTLSCKFSGSTFSSYYVSWVRQPPgkgleWLGYIGSNGSSYYQESYKGRFTiskdTSKNDVsLTISNLRVEDTGTYYC 79

First immunoglobulin variable (IgV) domain of poliovirus receptor (PVR, also known as CD155 and necl-5), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (necl-5)). Poliovirus (PV) binds to its cellular receptor (PVR/CD155) to initiate infection. CD155 is a membrane-anchored, single-span glycoprotein; its extracellular region has three Ig-like domains. There are four different isotypes of CD155 (referred to as alpha, beta, gamma, and delta), that result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted; CD155-alpha and CD155-delta are membrane-bound and function as PV receptors. The virus recognition site is contained in the amino-terminal domain, D1. Having the virus attachment site on the receptor distal from the plasma membrane may be important for successful initiation of infection of cells by the virus. CD155 binds in the poliovirus "canyon" with a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the first Ig-like domain of nectin-1 (also known as poliovirus receptor related protein(PVRL)1; CD111), nectin-3 (also known as PVRL 3), nectin-4 (also known as PVRL4; LNIR receptor)and DNAX accessory molecule 1 (DNAM-1; CD226).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228  38 GGSIILQCHL-SSTTAQVTQVNWEQQD----QLLAICNADLGWHISPSFKDRV---APGPGL---GLTLQSLTVNDTGEY 106
Cdd:cd05718   14 GGSVTLPCSLtSPGTTKITQVTWMKIGagssQNVAVFHPQYGPSVPNPYAERVeflAARLGLrnaTLRIRNLRVEDEGNY 93

                         90       100
                 ....*....|....*....|
gi 256600228 107 FCIYHTYPDGTYTGRIFLEV 126
Cdd:cd05718   94 ICEFATFPQGNRQGTTWLRV 113

First immunoglobulin variable (IgV) domain of nectin-2, nectin-like protein 5, and similar domains; The members here are composed of the second immunoglobulin (Ig) domain of nectin-2 (also known as poliovirus receptor related protein 2 or Cluster of Differentiation 112 (CD112)), nectin-like protein 5 (CD155), and similar proteins. Nectins and Nectin-like molecules are a family of Ca(2+)-independent immunoglobulin-like transmembrane glycoproteins belonging to the class of adhesion receptors, consisting of nine members (nectins 1 through 4 and nectin-like proteins 1 through 5). Nectins are synaptic cell adhesion molecules (CAMs) which facilitate adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. CD155 is the fifth member in the nectin-like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as Necl-5, or PVR. In contrast to all other family members, CD155 lacks self-adhesion capacity, yet it shares with nectins the feature to interact with other nectins. For instance, CD155 heterophilically trans-interacts with nectin-3, thereby contributing significantly to the establishment of adherens junctions between epithelial cells. This group belongs to the Constant 1 (C1)-set of IgSF domains, which has one beta-sheet that is formed by strands A-B-E-D and the other strands by G-F-C-C'.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228  38 GGSIILQCHLSS--TTAQVTQVNWEQQD--QLLAICNADLGwhisPSFK--DRVA-----PGPGL---GLTLQSLTVNDT 103
Cdd:cd20989   14 GGSVTLPCHLLPpnMVTHVSQVTWQRHDehGSVAVFHPKQG----PSFPesERLSfvaarLGAELrnaSLAMFGLRVEDE 89

                         90       100
                 ....*....|....*....|...
gi 256600228 104 GEYFCIYHTYPDGTYTGRIFLEV 126
Cdd:cd20989   90 GNYTCEFATFPQGSRSGDTWLRV 112

First immunoglobulin (Ig) domain of nectin-4, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-4 (also known as poliovirus receptor related protein 4 or LNIR receptor). Nectin-4 belongs to the nectin family, which is comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which participate in adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. For example nectin-4 trans-interacts with nectin-1. Nectin-4 has also been shown to interact with the actin filament-binding protein, afadin. Unlike the other nectins, which are widely expressed in adult tissues, nectin-4 is mainly expressed during embryogenesis, and is not detected in normal adult tissue or in serum. Nectin-4 is re-expressed in breast carcinoma, and patients having metastatic breast cancer have a circulating form of nectin-4 formed from the ectodomain

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228  33 ISAEKGGSIILQCHLS-STTAQVTQVNWEQQD-----QLLAICNADLGWHISPSFKDRV---APGPGL--GLTLQSLTVN 101
Cdd:cd05888    3 VTVVLGQDAKLPCFYRgDSGEQVGQVAWARVDagegaQEIALLHSKYGLHVFPAYEGRVeqpPPPRPAdgSVLLRNAVQA 82

                         90       100
                 ....*....|....*....|....*.
gi 256600228 102 DTGEYFCIYHTYPDGTYTGRIFLEVL 127
Cdd:cd05888   83 DEGEYECRVSTFPAGNFQAELRLRVL 108

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 256600228    40 SIILQCHLSSTTAQVTQVNWEQQDQ-----LLAICNADLGWHISPSFKDRVA----PGPGLG-LTLQSLTVNDTGEYFC 108
Cdd:smart00406   1 SVTLSCKFSGSTFSSYYVSWVRQPPgkgleWLGYIGSNGSSYYQESYKGRFTiskdTSKNDVsLTISNLRVEDTGTYYC 79

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228    31 GNISAEKGGSIILQCHLSSTTaqVTQVNWEQQDqllaicnadLGWHISPSFKDRVAPGPGLGLTLQSLTVNDTGEYFCIy 110
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSP--PPEVTWYKQG---------GKLLAESGRFSVSRSGSTSTLTISNVTPEDSGTYTCA- 69

                           90
                   ....*....|....*.
gi 256600228   111 HTYPDGTYTGRIFLEV 126
Cdd:smart00410  70 ATNSSGSASSGTTLTV 85

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        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 256600228   29 TTGNISAEKGGSIILQCHLSSTTAQVtQVNWEQQDQLLaicnaDLGWHISPSFKDRVapgpGLGLTLQSLTVNDTGEYFC 108
Cdd:pfam00047   2 APPTVTVLEGDSATLTCSASTGSPGP-DVTWSKEGGTL-----IESLKVKHDNGRTT----QSSLLISNVTKEDAGTYTC 71

                          90
                  ....*....|....*
gi 256600228  109 IYHTYPDGTYTGRIF 123
Cdd:pfam00047  72 VVNNPGGSATLSTSL 86

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 256600228  29 TTGNISAEKGGSIILqcHLSSTTAQVTQVNWEQQ------DQLLAICNADLGWHISPSFKDRVAPGPGLGLTLQSLTVND 102
Cdd:cd05741    1 SSEQFYGAEGKNVLL--LVPNLQTPLKSVSWYKGkqvsrnDEIAEYENSSDEFRAGSAFSGREYIYTNGSLLIQNITLSD 78

                 ....
gi 256600228 103 TGEY 106
Cdd:cd05741   79 TGFY 82