Identification of putative ligand binding sites within I domain of integrin alpha 2 beta 1 (VLA-2, CD49b/CD29)
Integrin alpha 2 beta 1 is a cell surface adhesion receptor for collagen and echovirus 1. Here we localized the epitopes for anti-alpha 2 monoclonal antibodies using interspecies (human/bovine) alpha 2 chimeras with different lengths of human alpha 2 sequence on the amino-terminal side and site-directed mutagenesis. The antibodies that block the collagen and/or echovirus 1 binding to human alpha 2 beta 1 (6F1, RMAC11, 12F1, and AA10) recognizes a small region (residues 173-259) within the I domain. Asp-160 and Arg-242 are critical for binding of the two other function-inhibiting antibodies, P1H5 and 5E8, respectively. Notably, mutations of Asp-151 and Asp-254 block the binding of alpha 2 beta 1 to collagen. These data suggest that the I domain (residues 140-359) is critically involved in the ligand/receptor interactions, and collagen and echovirus 1 binding sites are adjacent or overlapping within the I domain. The sequence of the residues 173-259 of alpha 2 overlap with the peptide sequences (M11 and M20) that derive from von Willebrand factor A1 and A3 domains (homologous to the alpha 2 I domain) and block von Willebrand factor/collagen interaction, suggesting that the epitope region of alpha 2 (residues 173-259) may really be involved in ligand recognition.
Kamata
T
T
Department of Vascular Biology, Scripps Research Institute, La Jolla, California 92037.
Puzon
W
W
Takada
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D002417:Cattle; D017124:Conserved Sequence; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D019012:Integrin beta1; D016023:Integrins / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D051379:Mice / Q000276:immunology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016029:Receptors, Very Late Antigen / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018076:DNA, Complementary; D019012:Integrin beta1; D016023:Integrins; D008024:Ligands; D016029:Receptors, Very Late Antigen; D011993:Recombinant Fusion Proteins