SecB与SecA再到SecY/E的结合级联反应介导前体蛋白靶向大肠杆菌质膜。

The binding cascade of SecB to SecA to SecY/E mediates preprotein targeting to the E. coli plasma membrane.

作者信息

Hartl F U, Lecker S, Schiebel E, Hendrick J P, Wickner W

机构信息

Molecular Biology Institute, University of California, Los Angeles 90024-1570.

出版信息

Cell. 1990 Oct 19;63(2):269-79. doi: 10.1016/0092-8674(90)90160-g.

DOI:10.1016/0092-8674(90)90160-g

PMID:2170023

Abstract

The export of many E. coli proteins such as proOmpA requires the cytosolic chaperone SecB and the membrane-bound preprotein translocase. Translocase is a multisubunit enzyme with the SecA protein as its peripheral membrane domain and the SecY/E protein as its integral domain. SecB, by binding to proOmpA in the cytosol, prevents its aggregation or association with membranes at nonproductive sites. The SecA receptor binds the proOmpA-SecB complex (Kd approximately 6 x 10(-8) M) through direct recognition of both the SecB (Kd approximately 2 x 10(-7) M) as well as the leader and mature domains of the precursor protein. SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway. SecA itself is bound to the membrane by its affinity (Kd approximately 4 x 10(-8) M) for SecY/E and for acidic lipids. The functions of SecB and SecA as a two-stage receptor system are linked by their affinity for each other.

摘要

许多大肠杆菌蛋白（如前OmpA）的输出需要胞质伴侣蛋白SecB和膜结合的前体蛋白转位酶。转位酶是一种多亚基酶，其外周膜结构域为SecA蛋白，其整合结构域为SecY/E蛋白。SecB通过在胞质溶胶中与前OmpA结合，防止其在非生产性位点聚集或与膜结合。SecA受体通过直接识别SecB（解离常数约为2×10⁻⁷M）以及前体蛋白的前导和成熟结构域，结合前OmpA-SecB复合物（解离常数约为6×10⁻⁸M）。SecB在稳定前体以及将其传递给膜结合的SecA（该途径的下一步）方面具有双重功能。SecA本身通过其对SecY/E和酸性脂质的亲和力（解离常数约为4×10⁻⁸M）与膜结合。SecB和SecA作为两阶段受体系统的功能通过它们彼此的亲和力联系在一起。