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 2172664193 147 FVDGSGEIGNDFKLKCEPKEGSLPLQYEWqkLSDSQKMPTPWLAEMT-----SPVISVKNASSEYSGTYSCTVQNRVGSD 221
Cdd:cd20959     9 FGEGAAQVGMRAQLHCGVPGGDLPLNIRW--TLDGQPISDDLGITVSrlgrrSSILSIDSLEASHAGNYTCHARNSAGSA 86

                  ....*...
gi 2172664193 222 QCMLRLDV 229
Cdd:cd20959    87 SYTAPLTV 94

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 2172664193  24 TPEQRIEKAKGETAYLPCKFTLEpEDQGPLDIEWLISPSDNQKvDQVIILYSGDkiyDNYYPDlKGRVHFTSnDVKSGDA 103
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSS-MSEASTSVYWYRQPPGKGP-TFLIAYYSNG---SEEGVK-KGRFSGRG-DPSNGDG 73

                          90       100       110
                  ....*....|....*....|....*....|....*.
gi 2172664193 104 SINVTNLQLSDIGTYQCKV-KKAPGVANRKFLLTVL 138
Cdd:pfam07686  74 SLTIQNLTLSDSGTYTCAViPSGEGVFGKGTRLTVL 109

Sixth 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 sixth 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 2172664193 147 FVDGSGEIGNDFKLKCEPKEGSLPLQYEWqkLSDSQKMPTPWLAEMT-----SPVISVKNASSEYSGTYSCTVQNRVGSD 221
Cdd:cd20959     9 FGEGAAQVGMRAQLHCGVPGGDLPLNIRW--TLDGQPISDDLGITVSrlgrrSSILSIDSLEASHAGNYTCHARNSAGSA 86

                  ....*...
gi 2172664193 222 QCMLRLDV 229
Cdd:cd20959    87 SYTAPLTV 94

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 2172664193 154 IGNDFKLKCEPKEGSLPLQYEWQK-----LSDSQKMPTPWlaEMTSPVISVKNASSEYSGTYSCTVQNRVGSDQ 222
Cdd:pfam00047  10 EGDSATLTCSASTGSPGPDVTWSKeggtlIESLKVKHDNG--RTTQSSLLISNVTKEDAGTYTCVVNNPGGSAT 81

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 2172664193  24 TPEQRIEKAKGETAYLPCKFTLEpEDQGPLDIEWLISPSDNQKvDQVIILYSGDkiyDNYYPDlKGRVHFTSnDVKSGDA 103
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSS-MSEASTSVYWYRQPPGKGP-TFLIAYYSNG---SEEGVK-KGRFSGRG-DPSNGDG 73

                          90       100       110
                  ....*....|....*....|....*....|....*.
gi 2172664193 104 SINVTNLQLSDIGTYQCKV-KKAPGVANRKFLLTVL 138
Cdd:pfam07686  74 SLTIQNLTLSDSGTYTCAViPSGEGVFGKGTRLTVL 109

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 2172664193  20 LSITTPEQrIEKAKGETAYLPCKFTLEPEDQGPLDIEWLISPsDNQKVDQVIILYSGDKIYDNYYPDLKGRVHFTSNDVK 99
Cdd:cd05715     1 MEVYTPRE-LNVLNGSDVRLTCTFTSCYTVGDAFSVTWTYQP-EGGNTTESMFHYSKGKPYILKVGRFKDRVSWAGNPSK 78

                          90       100
                  ....*....|....*....|....*..
gi 2172664193 100 SgDASINVTNLQLSDIGTYQCKVKKAP 126
Cdd:cd05715    79 K-DASIVISNLQFSDNGTYTCDVKNPP 104

Immunoglobulin (Ig)-like domain of chondroitin sulfate proteoglycans (CSPGs), human cartilage link protein (LP), and similar domains; The members here are composed of the immunoglobulin (Ig)-like domain similar to that found in chondroitin sulfate proteoglycans (CSPGs) and human cartilage link protein (LP). Included in this group are the CSPGs aggrecan, versican, and neurocan. In CSPGs, this Ig-like domain is followed by hyaluronan (HA)-binding tandem repeats, and a C-terminal region with epidermal growth factor-like, lectin-like, and complement regulatory protein-like domains. Separating these N- and C-terminal regions is a nonhomologous glycosaminoglycan attachment region. In cartilage, aggrecan forms cartilage link protein stabilized aggregates with hyaluronan (HA). These aggregates contribute to the tissue's load bearing properties. Aggrecan and versican have a wide distribution in connective tissue and extracellular matrices. Neurocan is localized almost exclusively in nervous tissue. Aggregates having other CSPGs substituting for aggrecan may contribute to the structural integrity of many different tissues. There is considerable evidence that HA-binding CSPGs are involved in developmental processes in the central nervous system. 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 2172664193  29 IEKAKGETAYLPCKFTLEPEDQGP----LDIEWLISPSDNQKVDQVIILYSGDKIYdNYYPDLKGRVHFTSNDVKSGDAS 104
Cdd:cd05714     7 VFSHLGGNVTLPCKFYRDPTAFGSgihkIRIKWTKLTSDSGYLKEVDVLVAMGNVV-YHKKTYGGRVSVPLKPGSDSDAS 85

                          90
                  ....*....|....*...
gi 2172664193 105 INVTNLQLSDIGTYQCKV 122
Cdd:cd05714    86 LVITDLTASDYGLYRCEV 103

Immunoglobulin variable domain (IgV) in Cluster of Differentiation (CD) 80; The members here are composed of the immunoglobulin variable region (IgV) in the Cluster of Differentiation (CD) 80). Glycoproteins B7-1 (also known as cluster of differentiation (CD) 80) and B7-2 (also known as CD86) are expressed on antigen-presenting cells and deliver the co-stimulatory signal through CD28 and CTLA-4 (also known as cluster of differentiation 152/CD152) on T cells. signaling through CD28 augments the T-cell response, whereas CTLA-4 signaling attenuates it. CD80 contains two Ig-like domains, an amino-terminal immunoglobulin variable (IgV)-like domain characteristic of adhesion molecules and a membrane proximal immunoglobulin constant (IgC)-like domain similar to the constant domains of antigen receptors. Members of the Ig family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and Major Histocompatibility Complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193  29 IEKAKGETAYLPCKFTLEPEDQGPLDIEWlispsdnQKVDQVII-LYSGDKiydNYYPDLKGRvhfTSNDVkSGDASINV 107
Cdd:cd16086     4 VTKSVKEKALLSCDYNVSVDELAQVRIYW-------QKDDKMVLtIISGDV---KVWPEYKNR---TLFDI-TNNLSIVI 69

                          90       100       110
                  ....*....|....*....|....*....|.
gi 2172664193 108 TNLQLSDIGTYQCKV-KKAPGVANRKFLLTV 137
Cdd:cd16086    70 LALRLSDRGTYTCVVqKKERGAYKREHLASV 100

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193   27 QRIEKAKGETAYLPCKFTLEPEDQgpldIEWLispsdnqKVDQVIILYSGdkiydnyypdlkgRVHFTSNdvkSGDASIN 106
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPE----VTWY-------KQGGKLLAESG-------------RFSVSRS---GSTSTLT 54

                           90       100       110
                   ....*....|....*....|....*....|.
gi 2172664193  107 VTNLQLSDIGTYQCKVKKAPGVANRKFLLTV 137
Cdd:smart00410  55 ISNVTPEDSGTYTCAATNSSGSASSGTTLTV 85

Immunoglobulin variable domain (IgV) in Cluster of Differentiation (CD) 86; The members here are composed of the immunoglobulin variable region (IgV) in the Cluster of Differentiation (CD) 86). Glycoproteins B7-1 (also known as cluster of differentiation (CD) 80) and B7-2 (also known as CD86) are expressed on antigen-presenting cells and deliver the co-stimulatory signal through CD28 and CTLA-4 (also known as CD152) on T cells. signaling through CD28 augments the T-cell response, whereas CTLA-4 signaling attenuates it. The CTLA-4 and B7-2 monomers are both two-layer beta-sandwiches that display the chain topology characteristic of the immunoglobulin variable (V-type) domains present in antigen receptors. The front and back sheets of B7-2 are composed of AGFCC'C" and BED strands, respectively. Members of the IgV family 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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193  34 GETAYLPCKFTlEPEDQGP--LDIEWlispsDNQKvDQVII-LYSGDKIYDNYYPDLKGRVHFTSNdvksgDASINVTNL 110
Cdd:cd16087     8 NETAYLPCQFK-NPQNISLseLVVFW-----QDQK-KLVLYeLYLGKEKLDNVNSKYIGRTSFDQE-----NWTLQLHNV 75

                          90
                  ....*....|
gi 2172664193 111 QLSDIGTYQC 120
Cdd:cd16087    76 QIKDQGTYQC 85

Sixth 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 sixth 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 2172664193 147 FVDGSGEIGNDFKLKCEPKEGSLPLQYEWqkLSDSQKMPTPWLAEMT-----SPVISVKNASSEYSGTYSCTVQNRVGSD 221
Cdd:cd20959     9 FGEGAAQVGMRAQLHCGVPGGDLPLNIRW--TLDGQPISDDLGITVSrlgrrSSILSIDSLEASHAGNYTCHARNSAGSA 86

                  ....*...
gi 2172664193 222 QCMLRLDV 229
Cdd:cd20959    87 SYTAPLTV 94

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 2172664193 154 IGNDFKLKCEPKEGSLPLQYEWQK-----LSDSQKMPTPWlaEMTSPVISVKNASSEYSGTYSCTVQNRVGSDQ 222
Cdd:pfam00047  10 EGDSATLTCSASTGSPGPDVTWSKeggtlIESLKVKHDNG--RTTQSSLLISNVTKEDAGTYTCVVNNPGGSAT 81

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193  21 SITTPEQRIEKAKGETAYLPCKFTLEPedqgPLDIEWLispsdnqKVDQVIIlysgdkiydnyyPDLKGRVHFtsndvKS 100
Cdd:pfam07679   2 KFTQKPKDVEVQEGESARFTCTVTGTP----DPEVSWF-------KDGQPLR------------SSDRFKVTY-----EG 53

                          90       100       110
                  ....*....|....*....|....*....|....*..
gi 2172664193 101 GDASINVTNLQLSDIGTYQCKVKKAPGVANRKFLLTV 137
Cdd:pfam07679  54 GTYTLTISNVQPDDSGKYTCVATNSAGEAEASAELTV 90

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 2172664193 158 FKLKCEPkEGSLPLQYEWQKLSDSQKMPTPWLAEMTSP--VISVKNASSEYSGTYSCTVQNRVG 219
Cdd:cd00096     1 VTLTCSA-SGNPPPTITWYKNGKPLPPSSRDSRRSELGngTLTISNVTLEDSGTYTCVASNSAG 63

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 2172664193  34 GETAYLPCKFTlEPEDQGPLDIEWLISPSDNQkvdQVIILYS---GDKIYDNYypdlKGRVHFTSNDVKSGDASINVTNL 110
Cdd:cd05718    14 GGSVTLPCSLT-SPGTTKITQVTWMKIGAGSS---QNVAVFHpqyGPSVPNPY----AERVEFLAARLGLRNATLRIRNL 85

                          90       100
                  ....*....|....*....|....*....
gi 2172664193 111 QLSDIGTYQCKVKKAPGvANRKFLLTVLV 139
Cdd:cd05718    86 RVEDEGNYICEFATFPQ-GNRQGTTWLRV 113

Immunoglobulin Variable region-containing chitin-binding proteins; an immunoglobulin V-set domain; The members here are composed of the immunoglobulin variable (IgV) region-containing chitin-binding proteins (VCBPs). VCBPs are secreted, immune-type molecules that have been identified in both amphioxus and sea squirt (Ciona intestinalis). VCBPs, which consist of a leader peptide, two tandem N-terminal immunoglobulin V-type domains and a single C-terminal chitin-binding domain, belong to a multigene family encoding secreted proteins. The VCBPs were identified first in the cephalochordate Branchiostoma floridae and show structural similarities with V-type domains of immunoglobulins and T cell receptors, suggesting that VCBPs represent a unique gut-associated form of innate immune proteins. 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, 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. 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 V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193  21 SITTPE-QRIEKAKGETAYLPCKFTLEPEDQGPLdIEWL--ISPSDNQKV---DQVIILYSGDkiYDNYYPDLKGRVHFT 94
Cdd:cd20963     3 TVTVPSyTRTDPTWGNRVELPCSYTISPAAQPPT-ITWLkgISVDRAEVVfkgFKYWNETSSS--GEVYFGDYAGRASVA 79

                          90       100
                  ....*....|....*....|....*...
gi 2172664193  95 SNDvksgDASINVTNLQLSDIGTYQCKV 122
Cdd:cd20963    80 SLT----QPTLVLTDLKFDDWGRYWCRV 103

Immunoglobulin (Ig)-like domain of protein zero (P0); 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 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.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193  84 YPDLKG----RVHFTSNDvKSGDASINVTNLQLSDIGTYQCKVKKAPGVANRKFLLTVLV 139
Cdd:cd05879    59 YIDNVGpfkeRIEWVGNP-SRKDGSIVIHNLDYTDNGTFTCDVKNPPDIVGKSSQVTLYV 117

Immunoglobulin (Ig) constant domain of the complement receptor of the immunoglobulin superfamily (CRIg); The members here are composed of the Immunoglobulin (Ig) constant domain of the complement receptor of the immunoglobulin superfamily (CRIg). The N-terminal domain of CRIg (also referred to as Z39Ig and V-set and Ig domain-containing 4 (VSIG4)) belongs to the IgV family of immunoglobulin-like domains while the C-terminal domain of CRIg belongs to the IgC family of immunoglobulin-like domains. CRIg plays a role in the complement system, an inhibitor of the alternative pathway convertases, and a negative regulator of T cell activation. 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 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2172664193 160 LKCEPKeGSLPLQYEWQKLSDSQKMPTPwLAEMTSPVIsvKNASSEYSGTYSCTVQNRVGSDQcmlRLDVV 230
Cdd:cd16082    18 LQCQAW-GSPPISYVWYKEQTNNQEPIK-VAALSTLLF--KPAVVADSGSYFCTAKGRVGSEQ---RSDIV 81

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2172664193 154 IGNDFKLKCEpKEGSLPLQYEWQK----LSDSQKMPTPWLAEMTSPVISvkNASSEYSGTYSCTVQNRVGSDQCMLRLDV 229
Cdd:pfam07679  14 EGESARFTCT-VTGTPDPEVSWFKdgqpLRSSDRFKVTYEGGTYTLTIS--NVQPDDSGKYTCVATNSAGEAEASAELTV 90

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.

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gi 2172664193 154 IGNDFKLKCEPKEGSLPlQYEWQKlsDSQKMPTPWLAEMTSP--VISVKNASSEYSGTYSCTVQNRVGSDQCMLRLDV 229
Cdd:cd05856    18 VGSSVRLKCVASGNPRP-DITWLK--DNKPLTPPEIGENKKKkwTLSLKNLKPEDSGKYTCHVSNRAGEINATYKVDV 92