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 2462586432  27 VNTEENVYATLGSDVNLTCQTQTVGF--FVQMQWSKVTNKI-DLIAVYHPQYGFycAYGRPCESLVTFTETPENGSKWTL 103
Cdd:cd05718     3 VQVPTEVTGFLGGSVTLPCSLTSPGTtkITQVTWMKIGAGSsQNVAVFHPQYGP--SVPNPYAERVEFLAARLGLRNATL 80

                          90       100
                  ....*....|....*....|...
gi 2462586432 104 HLRNMSCSVSGRYECMLVLYPEG 126
Cdd:cd05718    81 RIRNLRVEDEGNYICEFATFPQG 103

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 2462586432  27 VNTEENVYATLGSDVNLTCQTQTVGF--FVQMQWSKVTNKI-DLIAVYHPQYGFycAYGRPCESLVTFTETPENGSKWTL 103
Cdd:cd05718     3 VQVPTEVTGFLGGSVTLPCSLTSPGTtkITQVTWMKIGAGSsQNVAVFHPQYGP--SVPNPYAERVEFLAARLGLRNATL 80

                          90       100
                  ....*....|....*....|...
gi 2462586432 104 HLRNMSCSVSGRYECMLVLYPEG 126
Cdd:cd05718    81 RIRNLRVEDEGNYICEFATFPQG 103

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 2462586432  27 VNTEENVYATLGSDVNLTCQTQTVGF--FVQMQWSKVTNKI-DLIAVYHPQYGFycAYGRPCESLVTFTETPENGSKWTL 103
Cdd:cd05718     3 VQVPTEVTGFLGGSVTLPCSLTSPGTtkITQVTWMKIGAGSsQNVAVFHPQYGP--SVPNPYAERVEFLAARLGLRNATL 80

                          90       100
                  ....*....|....*....|...
gi 2462586432 104 HLRNMSCSVSGRYECMLVLYPEG 126
Cdd:cd05718    81 RIRNLRVEDEGNYICEFATFPQG 103

First immunoglobulin variable (IgV) domain of nectin-3 (also known as poliovirus receptor related protein 3), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3 (PVRL3) or cluster of differentiation (CD) 113). Nectin-3 belongs to the nectin family 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, during spermatid development, the nectin-3,-2 trans-interaction is required for the formation of Sertoli cell-spermatid junctions in testis, and during morphogenesis of the ciliary body, the nectin-3,-1 trans-interaction is important for apex-apex adhesion between the pigment and non-pigment layers of the ciliary epithelia. Nectins also heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls); nectin-3 for example, trans-interacts with Necl-5, regulating cell movement and proliferation. Other proteins with which nectin-3 interacts include the actin filament-binding protein, afadin, integrin alpha-beta3, Par-3, and PDGF receptor; its interaction with PDGF receptor regulates the latter's signaling for anti-apoptosis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2462586432  30 EENVYATLGSDVNLTCQTQTVGFFVQMQWSKVTNKI-DLIAVYHPQYGFycAYGRPCESLVTFTETPENGSkwTLHLRNM 108
Cdd:cd05887     6 EPHVTAVWGKNVSLKCLIEVNETITQISWEKIHGKSsQTVAVHHPQYGI--SIQGEYQGRVSFKNYSLNDA--TITLHNV 81

                          90
                  ....*....|....*...
gi 2462586432 109 SCSVSGRYECMLVLYPEG 126
Cdd:cd05887    82 GFSDSGKYICKAVTFPLG 99