A single amino acid substitution in SecY stabilizes the interaction with SecA

被引:17
作者
Manting, EH
Kaufmann, A
van der Does, C
Driessen, AJM
机构
[1] Univ Groningen, Dept Microbiol, NL-9751 NN Haren, Netherlands
[2] Univ Groningen, Groningen Biomol Sci & Biotechnol Inst, NL-9751 NN Haren, Netherlands
关键词
D O I
10.1074/jbc.274.34.23868
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The SecYEG complex constitutes a protein conducting channel across the bacterial cytoplasmic membrane. It binds the peripheral ATPase SecA to form the translocase. When isoleucine 278 in transmembrane segment 7 of the SecY subunit was replaced by a unique cysteine, SecYEG supported an increased preprotein translocation and SecA translocation ATPase activity, and allowed translocation of a preprotein with a defective signal sequence. SecY(I278C)EG binds SecA with a higher affinity than normal SecYEG, in particular in the presence of ATP. The increased translocation activity of SecY(1278C)EG was confirmed in a purified system consisting of SecYEG proteoliposomes, while immunoprecipitation in detergent solution reveal that translocase-preprotein complexes are more stable with SecY(I278C) than with normal SecY. These data imply an important role for SecY transmembrane segment 7 in SecA binding. As improved SecA binding to SecY was also observed with the prlA4 suppressor mutation, it may be a general mechanism underlying signal sequence suppression.
引用
收藏
页码:23868 / 23874
页数:7
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