Purified secB protein of Escherichia coli retards folding and promotes membrane translocation of the maltose-binding protein in vitro.
Purified secB protein of Escherichia coli retards folding and promotes membrane translocation of the maltose-binding protein in vitro.
复制标题
纯化的大肠杆菌 secB 蛋白可在体外延迟折叠并促进麦芽糖结合蛋白的膜易位。
DOI：
10.1073/pnas.85.23.8978
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发表时间：
1988
影响因子：
11.1
通讯作者：
BassfordJr,PJ
中科院分区：
文献类型：
--
作者：
Weiss,JB;Ray,PH;BassfordJr,PJ
大肠杆菌包膜蛋白子集的有效输出取决于 secB 基因的产物。先前的研究表明，SecB 通过防止细胞质中的前体 MBP 过早折叠成无输出能力的形式来促进周质麦芽糖结合蛋白 (MBP) 的输出。在这项研究中，SecB 已被纯化至均质，并被证明是由相同的 17 kDa 亚基组成的可溶性细胞质多聚体蛋白。 SecB 是 MBP 在体外有效转位到倒膜囊泡中所必需的。将纯化的 SecB 添加到由 SecB 细胞制备的体外系统中，显着增强了 MBP 易位。在没有膜的情况下，纯化的蛋白质还定量地延迟了前体 MBP 折叠成稳定的、耐蛋白酶的构象。最后，在 SecB+ 体外系统中加入过量的纯化 SecB 显着延长了前体 MBP 保持翻译后输入膜囊泡的能力的时间。
The efficient export of a subset of Escherichia coli envelope proteins is dependent upon the product of the secB gene. Previous studies indicated that SecB promotes the export of the periplasmic maltose-binding protein (MBP) by preventing premature folding of the precursor MBP in the cytoplasm into an export-incompetent form. In this study, SecB has been purified to homogeneity and shown to be a soluble, cytoplasmic, multimeric protein composed of identical 17-kDa subunits. SecB was required for efficient in vitro translocation of MBP into inverted membrane vesicles. The addition of purified SecB to an in vitro system prepared from SecB- cells significantly enhanced MBP translocation. The purified protein also quantitatively retarded folding of precursor MBP into a stable, protease-resistant conformation in the absence of membranes. Finally, the inclusion of excess purified SecB in a SecB+ in vitro system significantly prolonged the time in which precursor MBP remained competent for posttranslational import into membrane vesicles.