Defining the regions of Escherichia coli YidC that contribute to activity
Defining the regions of Escherichia coli YidC that contribute to activity
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DOI：
10.1074/jbc.m307362200
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发表时间：
2003-12-05
影响因子：
4.8
通讯作者：
Dalbey, RE
中科院分区：
文献类型：
--
作者：
Jiang, FL;Chen, MY;Dalbey, RE
YidC/Oxa1/Alb3蛋白家族在细菌、线粒体和叶绿体中催化膜蛋白插入。在这项研究中，我们研究了细菌YidC蛋白的哪些区域在膜蛋白的生物生成中起重要作用。在大肠杆菌中，YidC跨越膜6次，在第一个跨膜结构域之后有一个大的319个残基的质周结构域。我们发现这个大的外质结构域不是YidC功能所必需的，暴露的亲水性环或c端尾部的残基对YidC活性不是关键的。相反，包含YidC/ Oxa1/Alb3家族中三个共识序列的五个c端跨膜片段对其功能很重要。然而，通过系统地将跨膜片段（TM） 2、TM3和TM6中的所有残基替换为丝氨酸，并将TM4和TM5替换为不相关的跨膜片段，我们发现这些跨膜区域的精确序列对于体内YidC的活性并不是必需的。TM2、TM3和TM6的单丝氨酸突变破坏了sec独立的前衣前导肽酶蛋白的膜插入。我们提出，YidC的五个c端跨膜片段作为易位底物蛋白的平台，支持其插入到膜中。
The YidC/Oxa1/Alb3 family of proteins catalyzes membrane protein insertion in bacteria, mitochondria, and chloroplasts. In this study, we investigated which regions of the bacterial YidC protein are important for its function in membrane protein biogenesis. In Escherichia coli, YidC spans the membrane six times, with a large 319-residue periplasmic domain following the first transmembrane domain. We found that this large periplasmic domain is not required for YidC function and that the residues in the exposed hydrophilic loops or C-terminal tail are not critical for YidC activity. Rather, the five C-terminal transmembrane segments that contain the three consensus sequences in the YidC/ Oxa1/Alb3 family are important for its function. However, by systematically replacing all the residues in transmembrane segment (TM) 2, TM3, and TM6 with serine and by swapping TM4 and TM5 with unrelated transmembrane segments, we show that the precise sequence of these transmembrane regions is not essential for in vivo YidC activity. Single serine mutations in TM2, TM3, and TM6 impaired the membrane insertion of the Sec-independent procoat-leader peptidase protein. We propose that the five C-terminal transmembrane segments of YidC function as a platform for the translocating substrate protein to support its insertion into the membrane.