Manting E H, van der Does C, Driessen A J
Department of Microbiology, University of Groningen, Haren, The Netherlands.
J Bacteriol. 1997 Sep;179(18):5699-704. doi: 10.1128/jb.179.18.5699-5704.1997.
Precursor protein translocation across the Escherichia coli inner membrane is mediated by the translocase, which is composed of a heterotrimeric integral membrane protein complex with SecY, SecE, and SecG as subunits and peripherally bound SecA. Cross-linking experiments were conducted to study which proteins are associated with SecA in vivo. Formaldehyde treatment of intact cells results in the specific cross-linking of SecA to SecY. Concurrently with the increased membrane association of SecA, an elevated amount of cross-linked product was obtained in cells harboring overproduced SecYEG complex. Cross-linked SecA copurified with hexahistidine-tagged SecY and not with SecE. The data indicate that SecA and SecY coexist as a stable complex in the cytoplasmic membrane in vivo.
前体蛋白跨大肠杆菌内膜的转运由转运酶介导，该转运酶由一个异源三聚体整合膜蛋白复合物组成，其亚基为SecY、SecE和SecG以及外周结合的SecA。进行交联实验以研究体内哪些蛋白质与SecA相关联。完整细胞的甲醛处理导致SecA与SecY特异性交联。随着SecA膜结合增加，在过量表达SecYEG复合物的细胞中获得了更多的交联产物。交联的SecA与带有六组氨酸标签的SecY共纯化，而不与SecE共纯化。数据表明，SecA和SecY在体内作为一种稳定的复合物共存于细胞质膜中。
