Kamata T, Puzon W, Takada Y
Department of Vascular Biology, Scripps Research Institute, La Jolla, California 92037.
J Biol Chem. 1994 Apr 1;269(13):9659-63.
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.
整合素α2β1是胶原蛋白和埃可病毒1的细胞表面粘附受体。在此，我们利用在氨基末端侧具有不同长度人α2序列的种间（人/牛）α2嵌合体和定点诱变技术，定位了抗α2单克隆抗体的表位。阻断胶原蛋白和/或埃可病毒1与人α2β1结合的抗体（6F1、RMAC11、12F1和AA10）识别I结构域内的一个小区域（第173 - 259位氨基酸残基）。天冬氨酸-160和精氨酸-242分别对于另外两种功能抑制性抗体P1H5和5E8的结合至关重要。值得注意的是，天冬氨酸-151和天冬氨酸-254的突变会阻断α2β1与胶原蛋白的结合。这些数据表明I结构域（第140 - 359位氨基酸残基）在配体/受体相互作用中起关键作用，并且胶原蛋白和埃可病毒1的结合位点在I结构域内相邻或重叠。α2的第173 - 259位氨基酸残基序列与源自血管性血友病因子A1和A3结构域（与α2 I结构域同源）并阻断血管性血友病因子/胶原蛋白相互作用的肽序列（M11和M20）重叠，这表明α2的表位区域（第173 - 259位氨基酸残基）可能确实参与配体识别。
