Distinct catalytic roles of the SecYE, SecG and SecDFyajC subunits of preprotein translocase holoenzyme
Distinct catalytic roles of the SecYE, SecG and SecDFyajC subunits of preprotein translocase holoenzyme
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DOI：
10.1093/emboj/16.10.2756
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发表时间：
1997-05-15
期刊：
影响因子：
11.4
通讯作者：
Wickner, W
中科院分区：
文献类型：
--
作者：
Duong, F;Wickner, W
大肠杆菌前蛋白转位酶含有SecY、SecE和SecG（SecYEG）的膜包埋的三聚体复合物和外周SecA蛋白。SecYE是SecYEG复合物的保守的功能性“核心”，虽然足以提供SecA的高亲和力结合和膜插入位点，并且作为前蛋白依赖性ATP酶激活，但SecYE仅具有非常低的支持易位的能力。由secD操纵子编码的蛋白质-SecD、SecF和YajC-也形成完整的膜异源三聚体复合物（SecDFyajC）。物理和功能的研究表明，这两个三聚体复合物相关联，形成SecYEGDFyajC，六聚体的前蛋白转位酶'全酶'的膜结构域。SecG或SecDFyajC可以通过在易位反应的不同阶段促进SecA膜插入和去插入的ATP驱动循环来支持SecYE的易位活性。我们的研究结果表明，每个原核生物特异性亚基（SecA，SecG和SecDFyajC）一起发挥作用，以促进前蛋白的运动在SecYE核心的转位酶。
Escherichia coli preprotein translocase contains a membrane-embedded trimeric complex of SecY, SecE and SecG (SecYEG) and the peripheral SecA protein. SecYE is the conserved functional 'core' of the SecYEG complex, Although sufficient to provide sites for high-affinity binding and membrane insertion of SecA, and for its activation as a preprotein-dependent ATPase, SecYE has only very low capacity to support translocation, The proteins encoded by the secD operon-SecD, SecF and YajC-also form an integral membrane heterotrimeric complex (SecDFyajC). Physical and functional studies show that these two trimeric complexes are associated to form SecYEGDFyajC, the hexameric integral membrane domain of the preprotein translocase 'holoenzyme'. Either SecG or SecDFyajC can support the translocation activity of SecYE by facilitating the ATP-driven cycle of SecA membrane insertion and de-insertion at different stages of the translocation reaction. Our findings show that each of the prokaryote-specific subunits (SecA, SecG and SecDFyajC) function together to promote preprotein movement at the SecYE core of the translocase.