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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1214357801 147 PHCQIQGSQDIGSDVILLCSSEEGIPRPTYLWEKLDNTLKLPPTATQ---------DQVQGTVTIRNISALSSGAFF 214
Cdd:cd20950     1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRafsnssyslDPTTGELVFDPLSASDTGEYS 77

Immunoglobulin (Ig)-like domain of protein zero (P0) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of protein zero (P0), a myelin membrane adhesion molecule. P0 accounts for over 50% of the total protein in peripheral nervous system (PNS) myelin. P0 is a single-pass transmembrane glycoprotein with a highly basic intracellular domain and an extracellular Ig domain. The extracellular domain of P0 (P0-ED) is similar to the Ig variable domain, carrying one acceptor sequence for N-linked glycosylation. P0 plays a role in membrane adhesion in the spiral wraps of the myelin sheath. The intracellular domain is thought to mediate membrane apposition of the cytoplasmic faces and may, through electrostatic interactions, interact directly with lipid headgroups. It is thought that homophilic interactions of the P0 extracellular domain mediate membrane juxtaposition in the extracellular space of PNS myelin. This group also contains the Ig domain of sodium channel subunit beta-2 (SCN2B), and of epithelial V-like antigen 1 (EVA). EVA, also known as myelin protein zero-like 2, is an adhesion molecule, which may play a role in structural organization of the thymus and early lymphocyte development. SCN2B subunits play a role in determining sodium channel density and function in neurons,and in control of electrical excitability in the brain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  29 PGSIQVARGQPAVLPCTFTTSAALIN-LNVIWMVTPLsNANQPEQVILYQGGQMFDGAP-RFHGRVGFTGTMPATNVSIF 106
Cdd:cd05715     6 PRELNVLNGSDVRLTCTFTSCYTVGDaFSVTWTYQPE-GGNTTESMFHYSKGKPYILKVgRFKDRVSWAGNPSKKDASIV 84

                          90       100       110
                  ....*....|....*....|....*....|.
gi 1214357801 107 INNTQLSDTGTYQCLVNNLPDIggrnIGVTG 137
Cdd:cd05715    85 ISNLQFSDNGTYTCDVKNPPDI----VGGHG 111

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. 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 second Ig-like domain of JAM1 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, the A strand of the I-set is discontinuous but lacks 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1214357801 147 PHCQIQGSQDIGSDVILLCSSEEGIPRPTYLWEKLDNTLKLPPTATQ---------DQVQGTVTIRNISALSSGAFF 214
Cdd:cd20950     1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRafsnssyslDPTTGELVFDPLSASDTGEYS 77

Immunoglobulin (Ig)-like domain of protein zero (P0) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of protein zero (P0), a myelin membrane adhesion molecule. P0 accounts for over 50% of the total protein in peripheral nervous system (PNS) myelin. P0 is a single-pass transmembrane glycoprotein with a highly basic intracellular domain and an extracellular Ig domain. The extracellular domain of P0 (P0-ED) is similar to the Ig variable domain, carrying one acceptor sequence for N-linked glycosylation. P0 plays a role in membrane adhesion in the spiral wraps of the myelin sheath. The intracellular domain is thought to mediate membrane apposition of the cytoplasmic faces and may, through electrostatic interactions, interact directly with lipid headgroups. It is thought that homophilic interactions of the P0 extracellular domain mediate membrane juxtaposition in the extracellular space of PNS myelin. This group also contains the Ig domain of sodium channel subunit beta-2 (SCN2B), and of epithelial V-like antigen 1 (EVA). EVA, also known as myelin protein zero-like 2, is an adhesion molecule, which may play a role in structural organization of the thymus and early lymphocyte development. SCN2B subunits play a role in determining sodium channel density and function in neurons,and in control of electrical excitability in the brain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  29 PGSIQVARGQPAVLPCTFTTSAALIN-LNVIWMVTPLsNANQPEQVILYQGGQMFDGAP-RFHGRVGFTGTMPATNVSIF 106
Cdd:cd05715     6 PRELNVLNGSDVRLTCTFTSCYTVGDaFSVTWTYQPE-GGNTTESMFHYSKGKPYILKVgRFKDRVSWAGNPSKKDASIV 84

                          90       100       110
                  ....*....|....*....|....*....|.
gi 1214357801 107 INNTQLSDTGTYQCLVNNLPDIggrnIGVTG 137
Cdd:cd05715    85 ISNLQFSDNGTYTCDVKNPPDI----VGGHG 111

Immunoglobulin (Ig)-like domain of epithelial V-like antigen (EVA) 1; The members here are composed of the immunoglobulin (Ig) domain of epithelial V-like antigen 1 (EVA 1). EVA is also known as myelin protein zero-like 2. EVA is an adhesion molecule and may play a role in the structural organization of the thymus and early lymphocyte development.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  28 SPGSIQVARGQPAVLPCTFTTSAALIN-LNVIWMVTPLSNAnqPEQVILYQGGQMF---DGapRFHGRVGFTGTMPATNV 103
Cdd:cd05880     5 TSKEVEAVNGTDVRLKCTFSSSAPIGDtLVITWNFRPLDGG--REESVFYYHKRPYpppDG--RFKGRVVWDGNIMRRDA 80

                          90       100
                  ....*....|....*....|....*..
gi 1214357801 104 SIFINNTQLSDTGTYQCLVNNLPDIGG 130
Cdd:cd05880    81 SILIWQLQPTDNGTYTCQVKNPPDVHG 107

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801   29 PGSIQVARGQPAVLPCTFTTSAaliNLNVIWMvtplsnaNQPEQVILYQGGqmfdgaprfhgrvgFTGTMPATNVSIFIN 108
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSP---PPEVTWY-------KQGGKLLAESGR--------------FSVSRSGSTSTLTIS 56

                           90
                   ....*....|....*.
gi 1214357801  109 NTQLSDTGTYQCLVNN 124
Cdd:smart00410  57 NVTPEDSGTYTCAATN 72

Immunoglobulin (Ig)-like domain of human cartilage link protein (LP), and similar domains; The members here are composed of the immunoglobulin (Ig)-like domain similar to that found in human cartilage link protein (LP; also called hyaluronan and proteoglycan link protein). In cartilage, chondroitin-keratan sulfate proteoglycan (CSPG), aggrecan, forms cartilage link protein stabilized aggregates with hyaluronan (HA). These aggregates contribute to the tissue's load bearing properties. Aggregates having other CSPGs substituting for aggrecan may contribute to the structural integrity of many different tissues. Members of the vertebrate HPLN (hyaluronan/HA and proteoglycan binding link) protein family are physically linked adjacent to CSPG genes.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  26 SESPGSIQVARGQPAVLPCTFTTSAALINLN---VIWmvTPLSNANQPEQVILYQGGQMFDGAPRFHGRVGFTGTMPaTN 102
Cdd:cd05877     1 ETVQAKVFSHRGGNVTLPCRYHYEPELSAPRkirVKW--TKLEVDYAKEEDVLVAIGTRHKSYGSYQGRVFLRRADD-LD 77

                          90       100
                  ....*....|....*....|....*.
gi 1214357801 103 VSIFINNTQLSDTGTYQC-LVNNLPD 127
Cdd:cd05877    78 ASLVITDLRLEDYGRYRCeVIDGLED 103

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 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" strands in the other.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  25 VSESPGSIQVARGQPAVLPCTFTTSaaLINLNVIWMVTPLsnaNQPEQVILYQGGQMFDGAPRFHGRvgFTGTMPATNVS 104
Cdd:cd00099     1 VTQSPRSLSVQEGESVTLSCEVSSS--FSSTYIYWYRQKP---GQGPEFLIYLSSSKGKTKGGVPGR--FSGSRDGTSSF 73

                          90
                  ....*....|....*..
gi 1214357801 105 IF-INNTQLSDTGTYQC 120
Cdd:cd00099    74 SLtISNLQPEDSGTYYC 90

Immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG); The members here are composed of the immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG). MOG, a minor component of the myelin sheath, is an important CNS-specific autoantigen, linked to the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). It is a transmembrane protein having an extracellular Ig domain. MOG is expressed in the CNS on the outermost lamellae of the myelin sheath, and on the surface of oligodendrocytes, and may participate in the completion, compaction, and/or maintenance of myelin. This group also includes butyrophilin (BTN). BTN is the most abundant protein in bovine milk-fat globule membrane (MFGM).

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  31 SIQVARGQPAVLPCTFTTSAALINLNVIWMVTPLSNAnqpeqVILYQGGQMFDG--APRFHGRVGFT-GTMPATNVSIFI 107
Cdd:cd05713     9 PILALVGEDAELPCHLSPKMSAEHMEVRWFRSQFSPV-----VHLYRDGQDQEEeqMPEYRGRTELLkDAIAEGSVALRI 83

                          90
                  ....*....|....*.
gi 1214357801 108 NNTQLSDTGTYQCLVN 123
Cdd:cd05713    84 HNVRPSDEGQYTCFFR 99

Immunoglobulin Variable (IgV) domain in HERV-H LTR-associating 2 (HHLA2); The members here are composed of the immunoglobulin variable (IgV) region in HERV-H LTR-associating 2 (HHLA2; also known as B7-H7/B7 homolog 7). HHLA2 is a member of the B7 family of immune regulatory proteins. Mature human HHLA2 consists of an extracellular domain (ECD) with three immunoglobulin-like domains, a transmembrane segment, and a cytoplasmic domain. HHLA2 is widely expressed in human cancers including non-small cell lung carcinoma (NSCLS), triple negative breast cancer (TNBC), and melanoma, but has limited expression on normal tissues. Interestingly, unlike other members of B7 family, HHLA2 is not expressed in mice or rats. HHLA2 functions as a T cell coinhibitory molecules as it inhibits the proliferation of activated CD4(+) and CD8(+) T cells and their cytokine production. Furthermore, HHLA2 is constitutively expressed on the surface of human monocytes and is induced on B cells after stimulation, however it is not inducible on T cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  41 VLPCTFTTSAALInlnVIWMVtplSNANQPEQVILYQGGQMFDGAPRFHGRVG-FTGTMPATNVSIFINNTQLSDTGTYQ 119
Cdd:cd16091    16 ILPCSFTPGSEVV---IHWYK---QDSDIKVHSYYYGKDQLESQDQRYRNRTSlFKDQISNGNASLLLRRVQLQDEGRYK 89

                  ....*
gi 1214357801 120 CLVNN 124
Cdd:cd16091    90 CYTST 94

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 1214357801  37 GQPAVLPCTFTTSAALINLNVIWMvtpLSNANQPEQVILYQGGQMFDGAPRFHGRVGFT-GTMPATNVSIFINNTQLSDT 115
Cdd:cd05718    14 GGSVTLPCSLTSPGTTKITQVTWM---KIGAGSSQNVAVFHPQYGPSVPNPYAERVEFLaARLGLRNATLRIRNLRVEDE 90

                          90       100
                  ....*....|....*....|....*
gi 1214357801 116 GTYQCLVNNLPdiGGRNIGVTGLTV 140
Cdd:cd05718    91 GNYICEFATFP--QGNRQGTTWLRV 113

First immunoglobulin (Ig) variable (V) domain of rat MRC OX-2 antigen, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of rat MRC OX-2 antigen (also known as CD200) and similar proteins. MRC OX-2 is a membrane glycoprotein expressed in a variety of lymphoid and non-lymphoid cells in rats. It has a similar broad distribution pattern in humans. MRC OX-2 may regulate myeloid cell activity. The protein has an extracellular portion containing two Ig-like domains, a transmembrane portion, and a cytoplasmic portion.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  37 GQPAVLPCTFTTSAALinLNVIWMVTplsNANQPEQVILYQGGQMFDGAPRFHGRVGFTGTMPaTNVSIFINNTQLSDTG 116
Cdd:cd05846    13 GGNATLSCNLTLPEEV--LQVTWQKI---KASSPENIVTYSKKYGVKIQPSYVRRISFTSSGL-NSTSITIWNVTLEDEG 86

                          90       100
                  ....*....|....*....|....
gi 1214357801 117 TYQCLVNNLPDigGRNIGVTGLTV 140
Cdd:cd05846    87 CYKCLFNTFPD--GIKSGTACLTV 108

First immunoglobulin variable (IgV) domain of DNAX accessory molecule 1, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of DNAX accessory molecule 1 (DNAM-1, also known as CD226). DNAM-1 is a transmembrane protein having two Ig-like domains. It is an adhesion molecule which plays a part in tumor-directed cytotoxicity and adhesion in natural killer (NK) cells and T lymphocytes. It has been shown to regulate the NK cell killing of several tumor types, including myeloma cells and ovarian carcinoma cells. DNAM-1 interacts specifically with poliovirus receptor (PVR; CD155) and nectin -2 (CD211), other members of the Ig superfamily. DNAM-1 is expressed in most peripheral T cells, NK cells, monocytes and a subset of B lymphocytes.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  41 VLPCTFTTSAALINlnVIWMVTPlsnaNQPEQVILY--QGGQMFDgaPRFHGRVGF-TGTMPATNVSIFINNTQLSDTGT 117
Cdd:cd05889    18 SLECVYPSTGILTQ--VEWTKIG----GQKDNIAVYhpTHGMHIR--KPYAGRVYFlNSTMASNNMSLSFRNASEDDVGY 89

                          90
                  ....*....|
gi 1214357801 118 YQCLVNNLPD 127
Cdd:cd05889    90 YSCSLYTYPQ 99

Immunoglobulin Variable (IgV) domain at the N-terminus of CD33 and related Siglecs (sialic acid-binding Ig-like lectins); The members here are composed of the immunoglobulin (Ig) domain at the N-terminus of Cluster of Differentiation (CD) 33 and related Siglecs (sialic acid-binding Ig-like lectins). Siglec refers to a structurally related protein family that specifically recognizes sialic acid in oligosaccharide chains of glycoproteins and glycolipids. Siglecs are type I transmembrane proteins, organized as an extracellular module composed of Ig-like domains, an N-terminal variable set of Ig-like carbohydrate recognition domains, and 1 to 16 constant Ig-like domains, followed by transmembrane and short cytoplasmic domains. Human Siglecs are classified into two subgroups, one subgroup is comprised of sialoadhesin (Siglec-1), CD22 (Siglec-2), and MAG, the other subgroup is comprised of CD33-related Siglecs which include CD33 (Siglec-3) and human Siglecs 5-11.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1214357801  27 ESPGSIQVARGQPAVLPCTFT------TSAALInlnVIW--------MVTPLSNANQPEQVilyqggqmfdgAPRFHGRV 92
Cdd:cd05712     4 QMPKSVTVQEGLCVLIPCSFSypadywVSNPVH---GYWyrggpypkYRPPVATNNRTREV-----------HESTQGRF 69

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|.
gi 1214357801  93 GFTGTMPATNVSIFINNTQLSDTGTYQCLVnnlpDIGGRNI 133
Cdd:cd05712    70 RLLGDPGKKNCSLSISDARPEDSGKYFFRV----ERGDSNK 106

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. 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 second Ig-like domain of JAM1 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, the A strand of the I-set is discontinuous but lacks 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1214357801 147 PHCQIQGSQDIGSDVILLCSSEEGIPRPTYLWEKLDNTLKLPPTATQ---------DQVQGTVTIRNISALSSGAFF 214
Cdd:cd20950     1 PTVNIPSSATIGNRAVLTCSEPDGSPPSEYTWFKDGVVMPTNPKSTRafsnssyslDPTTGELVFDPLSASDTGEYS 77