Saltman L H, Lu Y, Zaharias E M, Isberg R R
Howard Hughes Medical Institute, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
J Biol Chem. 1996 Sep 20;271(38):23438-44. doi: 10.1074/jbc.271.38.23438.
The entry of Yersinia pseudotuberculosis into cultured mammalian cells is mediated by the bacterial protein invasin. The mammalian receptors for invasin are five beta1 chain integrins. Site-directed mutagenesis of the aspartate and lysine residues in the 192-amino acid integrin binding domain of invasin was performed to identify regions, in addition to the previously characterized 903-913 region, that are important for integrin binding. One mutation, D811A, resulted in depressed ability of invasin to bind purified alpha5beta1 and to promote bacterial entry. Further mutational analysis of Asp-811 indicated that an oxygen-containing side chain is required at this position. A second nearby residue, Phe-808, was also shown to be important for integrin binding, as an alanine substitution at this site had properties similar to the Asp-811 mutation. This mutational analysis has therefore identified a second region that, in conjunction with residues 903-913, is required for wild type levels of integrin binding. The contribution to binding by two noncontiguous sites in the primary sequence parallels results that indicate two domains of fibronectin are involved in integrin binding.
假结核耶尔森菌进入培养的哺乳动物细胞是由细菌蛋白侵袭素介导的。侵袭素的哺乳动物受体是五种β1链整合素。对侵袭素192个氨基酸的整合素结合结构域中的天冬氨酸和赖氨酸残基进行定点诱变，以确定除先前鉴定的903 - 913区域外，对整合素结合重要的区域。一个突变体D811A导致侵袭素结合纯化的α5β1以及促进细菌进入的能力降低。对天冬氨酸811的进一步诱变分析表明该位置需要一个含氧侧链。另一个附近的残基苯丙氨酸808也被证明对整合素结合很重要，因为该位点的丙氨酸替代具有与天冬氨酸811突变相似的特性。因此，这种诱变分析确定了第二个区域，该区域与903 - 913残基一起，是整合素结合达到野生型水平所必需的。一级序列中两个不相邻位点对结合的贡献与表明纤连蛋白的两个结构域参与整合素结合的结果相似。
