Driessen A J, Fekkes P, van der Wolk J P
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
Curr Opin Microbiol. 1998 Apr;1(2):216-22. doi: 10.1016/s1369-5274(98)80014-3.
Proteins designated to be secreted by Escherichia coli are synthesized with an amino-terminal signal peptide and associate as nascent chains with the export-specific chaperone SecB. Translocation occurs at a multisubunit membrane-bound enzyme termed translocase, which consists of a peripheral preprotein-binding site and an ATPase domain termed SecA, a core heterotrimeric integral membrane protein complex with SecY, SecE and SecG as subunits, and an accessory integral membrane protein complex containing SecD and SecF. Major new insights have been gained into the cascade of preprotein targeting events and the enzymatic mechanism or preprotein translocation. It has become clear that preproteins are translocated in a stepwise fashion involving large nucleotide-induced conformational changes of the molecular motor SecA that propels the translocation reaction.
指定由大肠杆菌分泌的蛋白质在合成时带有氨基末端信号肽，并作为新生链与出口特异性伴侣蛋白SecB结合。转运发生在一种称为转位酶的多亚基膜结合酶上，该酶由一个外周前体蛋白结合位点和一个称为SecA的ATP酶结构域、一个以SecY、SecE和SecG为亚基的核心异源三聚体整合膜蛋白复合物以及一个包含SecD和SecF的辅助整合膜蛋白复合物组成。关于前体蛋白靶向事件的级联反应和前体蛋白转运的酶促机制已经有了重大的新见解。很明显，前体蛋白以逐步方式进行转运，这涉及分子马达SecA的由大的核苷酸诱导的构象变化，该变化推动了转运反应。
