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 768015805   43 FTETPHDMTARTGEDVEMACSFRGSGSPsyslEIQWWYvrshrdwtDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGT 122
Cdd:pfam07679   3 FTQKPKDVEVQEGESARFTCTVTGTPDP----EVSWFK--------DGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGK 70

                  ....*
gi 768015805  123 YECRV 127
Cdd:pfam07679  71 YTCVA 75

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768015805   43 FTETPHDMTARTGEDVEMACSFRGSGSPsyslEIQWWYvrshrdwtDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGT 122
Cdd:pfam07679   3 FTQKPKDVEVQEGESARFTCTVTGTPDP----EVSWFK--------DGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGK 70

                  ....*
gi 768015805  123 YECRV 127
Cdd:pfam07679  71 YTCVA 75

Immunoglobulin-like Ig0 domain of basigin-1 (BSG1) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of the collagenase stimulatory factor, basigin-1 (BSG1; also known as Cluster of Differentiation 147 (CD147) and Extracellular Matrix Metalloproteinase Inducer (EMMPRIN)) and similar proteins. CD147 is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It is expressed in nearly all cells including platelets and fibroblasts and is involved in inflammatory diseases, and cancer progression. CD147 is highly expressed in several cancers and used as a prognostic marker. The two primary isoforms of CD147 that are related to cancer progression have been identified: CD147 Ig1-Ig2 (also called Basigin-2) that is ubiquitously expressed in most tissues and CD147 Ig0-Ig1-Ig2 (also called Basigin-1) that is retinal specific and implicated in retinoblastoma. Studies showed that CD147 Ig0 domain is a potent stimulator of interleukin-6 and suggest that the CD147 Ig0 dimer is the functional unit required for activity.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768015805  41 ALFTETPHDMTARTGEDVEMACSFRGSGSPsyslEIQWWYVRSHRDWTDKQAW--ASNQVVKVVGSNISH---KLRLSRV 115
Cdd:cd20940    1 AGFIKSPLSQQRLVGDSVELHCEAVGSPIP----EIQWWFEGQEPNEICSQLWdgARLDRVHINATYHQHatsTISIDNL 76

                         90       100       110
                 ....*....|....*....|....*....|....*..
gi 768015805 116 KPTDEGTYECRVidfSDGKARHH-----KVKaYLRVQ 147
Cdd:cd20940   77 TEEDTGTYECRA---SNDPDRNHltrapKVK-WIRSQ 109

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768015805   43 FTETPHDMTARTGEDVEMACSFRGSGSPsyslEIQWWYvrshrdwtDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGT 122
Cdd:pfam07679   3 FTQKPKDVEVQEGESARFTCTVTGTPDP----EVSWFK--------DGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGK 70

                  ....*
gi 768015805  123 YECRV 127
Cdd:pfam07679  71 YTCVA 75

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768015805   43 FTETPHDMTARTGEDVEMACSFRGSGSPSYsleiqWWYVrshrdwtDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGT 122
Cdd:pfam13927   4 ITVSPSSVTVREGETVTLTCEATGSPPPTI-----TWYK-------NGEPISSGSTRSRSLSGSNSTLTISNVTRSDAGT 71

                  ....*
gi 768015805  123 YECRV 127
Cdd:pfam13927  72 YTCVA 76

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 768015805   45 ETPHDMTARTGEDVEMACSFrgsgSPSYSLEIQW--WYvRSHRDWTDKQA---WASNQVVKVVG-----------SNISh 108
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTY----SSSMSEASTSvyWY-RQPPGKGPTFLiayYSNGSEEGVKKgrfsgrgdpsnGDGS- 74

                          90       100
                  ....*....|....*....|....*
gi 768015805  109 kLRLSRVKPTDEGTYECRVIDFSDG 133
Cdd:pfam07686  75 -LTIQNLTLSDSGTYTCAVIPSGEG 98

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. 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 this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus 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 768015805  43 FTETPHDMTARTGEDVEMACSFRGSGSPsyslEIQWwyVRSHRDWTdkQAWASNQVVKVVGsnishKLRLSRVKPTDEGT 122
Cdd:cd20976    4 FSSVPKDLEAVEGQDFVAQCSARGKPVP----RITW--IRNAQPLQ--YAADRSTCEAGVG-----ELHIQDVLPEDHGT 70

                 ...
gi 768015805 123 YEC 125
Cdd:cd20976   71 YTC 73

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. 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, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), 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 Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 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.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768015805  44 TETPHDMTARTGEDVEMACsfRGSGSPSYSLEiqwWYVRSHRDWTDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGTY 123
Cdd:cd07693    4 VEHPSDLIVSKGDPATLNC--KAEGRPTPTIQ---WLKNGQPLETDKDDPRSHRIVLPSGSLFFLRVVHGRKGRSDEGVY 78

                 ..
gi 768015805 124 EC 125
Cdd:cd07693   79 VC 80

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 768015805   55 GEDVEMACSFRGSGSPsysLEIQWWYvrshrdwTDKQAWASNQVVKVVGSNISHKLRLSRVKPTDEGTYECRV 127
Cdd:pfam00047  11 GDSATLTCSASTGSPG---PDVTWSK-------EGGTLIESLKVKHDNGRTTQSSLLISNVTKEDAGTYTCVV 73