Leong J M, Morrissey P E, Marra A, Isberg R R
Department of Medicine, Tufts-New England Medical Center Hospital, Boston, MA.
EMBO J. 1995 Feb 1;14(3):422-31. doi: 10.1002/j.1460-2075.1995.tb07018.x.
The Yersinia pseudotuberculosis invasin protein mediates bacterial entry into mammalian cells by binding multiple beta 1-chain integrins. Invasin binding to purified alpha 5 beta 1 integrin is inhibited by Arg-Gly-Asp (RGD)-containing peptides, although invasin contains no RGD sequence. Fifteen mutations that diminished binding and bacterial entry were isolated after mutagenesis of the entire inv gene. All of the mutations altered residues within the C-terminal 192 amino acids of invasin, previously delineated as the integrin binding domain, and 10 of the mutations fell within an 11 residue region. This small region was subjected to site-directed mutagenesis and almost half of the 35 mutations generated decreased invasin-mediated entry. D911 within this region was the most critical residue, as even a conservative glutamate substitution abolished bacterial penetration. Purified invasin derivatives altered at this residue were defective in promoting cell attachment and this defect was reflected in a 10-fold or greater increase in IC50 for integrin binding. D911 may have a function similar to that of the aspartate residue in RGD-containing sequences.
耶尔森氏假结核菌侵袭蛋白通过结合多种β1链整合素来介导细菌进入哺乳动物细胞。尽管侵袭蛋白不含精氨酸-甘氨酸-天冬氨酸（RGD）序列，但与纯化的α5β1整合素的结合会受到含RGD肽的抑制。对整个inv基因进行诱变后，分离出了15个减少结合和细菌进入的突变。所有突变均改变了侵袭蛋白C末端192个氨基酸内的残基，该区域先前被划定为整合素结合域，其中10个突变位于一个11个残基的区域内。对该小区域进行定点诱变，所产生的35个突变中近一半降低了侵袭蛋白介导的进入。该区域内的D911是最关键的残基，因为即使是保守的谷氨酸替代也消除了细菌的穿透。在此残基处发生改变的纯化侵袭蛋白衍生物在促进细胞附着方面存在缺陷，并且这种缺陷反映在整合素结合的IC50增加了10倍或更多。D911可能具有与含RGD序列中天冬氨酸残基类似的功能。
