Yauch R L, Kazarov A R, Desai B, Lee R T, Hemler M E
Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Biol Chem. 2000 Mar 31;275(13):9230-8. doi: 10.1074/jbc.275.13.9230.
Previously we established that the alpha(3)beta(1) integrin shows stable, specific, and stoichiometric association with the TM4SF (tetraspannin) protein CD151. Here we used a membrane impermeable cross-linking agent to show a direct association between extracellular domains of alpha(3)beta(1) and CD151. The alpha(3)beta(1)-CD151 association site was then mapped using chimeric alpha(6)/alpha(3) integrins and CD151/NAG2 TM4SF proteins. Complex formation required an extracellular alpha(3) site (amino acids (aa) 570-705) not previously known to be involved in specific integrin contacts with other proteins and a region (aa 186-217) within the large extracellular loop of CD151. Notably, the anti-CD151 monoclonal antibody TS151r binding epitope, previously implicated in alpha(3) integrin association, was mapped to the same region of CD151 (aa 186-217). Finally, we demonstrated that both NH(2)- and COOH-terminal domains of CD151 are located on the inside of the plasma membrane, thus confirming a long suspected model of TM4SF protein topology.
此前我们证实，α(3)β(1)整合素与TM4SF（四跨膜蛋白）蛋白CD151呈现稳定、特异且化学计量的结合。在此我们使用一种膜不可渗透的交联剂来显示α(3)β(1)和CD151的胞外结构域之间存在直接结合。然后利用嵌合的α(6)/α(3)整合素和CD151/NAG2 TM4SF蛋白对α(3)β(1)-CD151结合位点进行定位。复合物形成需要一个胞外α(3)位点（氨基酸(aa) 570 - 705），该位点此前未知参与整合素与其他蛋白的特异性接触，以及CD151大胞外环内的一个区域（aa 186 - 217）。值得注意的是，先前认为与α(3)整合素结合有关的抗CD151单克隆抗体TS151r的结合表位被定位到CD151的同一区域（aa 186 - 217）。最后，我们证明CD151的NH₂-末端和COOH-末端结构域均位于质膜内侧，从而证实了长期以来备受怀疑的TM4SF蛋白拓扑结构模型。
