Oliver D B, Beckwith J
Cell. 1982 Aug;30(1):311-9. doi: 10.1016/0092-8674(82)90037-x.
We have previously described a gene, secA, which may code for a component of the secretion machinery of E. coli. Temperature-sensitive mutations in this gene lead to the cytoplasmic accumulation of precursors to a number of secreted proteins. In this paper, we describe the use of antibody to the SecA protein to characterize the cellular location and regulation of the protein. The antibody was elicited in response to a SecA-LacZ hybrid protein, produced by a strain carrying a secA-lacZ gene fusion. The secA gene product is a 92 kd polypeptide that is present in small amounts in the cell and that fractionates as a peripheral cytoplasmic membrane protein. The synthesis of the SecA protein is greatly derepressed (at least tenfold) when secretion in E. coli is blocked either in a secAts mutant or in the presence of a MalE-LacZ hybrid protein. We suggest that components of the secretion machinery of E. coli, such as the SecA protein, may be regulated in response to the secretion needs of the cell. When suppression of a secAam mutant is eliminated, leading to the absence of SecA protein, the synthesis of maltose-binding protein is greatly reduced. These results support a mechanism in which secretion and translation are coupled.
我们之前描述过一个基因，secA，它可能编码大肠杆菌分泌机制的一个组成部分。该基因中的温度敏感突变会导致多种分泌蛋白的前体在细胞质中积累。在本文中，我们描述了使用针对SecA蛋白的抗体来表征该蛋白的细胞定位和调控。该抗体是由携带secA-lacZ基因融合的菌株产生的SecA-LacZ杂合蛋白诱导产生的。secA基因产物是一种92kd的多肽，在细胞中含量较少，作为外周细胞质膜蛋白进行分级分离。当在secAts突变体中或在存在MalE-LacZ杂合蛋白的情况下阻断大肠杆菌中的分泌时，SecA蛋白的合成会大大去阻遏（至少十倍）。我们认为，大肠杆菌分泌机制的组成部分，如SecA蛋白，可能会根据细胞的分泌需求进行调控。当消除secAam突变体的抑制作用，导致SecA蛋白缺失时，麦芽糖结合蛋白的合成会大大减少。这些结果支持了一种分泌与翻译偶联的机制。
