Weaver C A, Redborg A H, Konisky J
J Bacteriol. 1981 Dec;148(3):817-28. doi: 10.1128/jb.148.3.817-828.1981.
The colicin Ia structural (cia) and immunity (iia) genes of plasmid pColIa-CA53 have been cloned into the cloning vector pBR322. These two genes are closely linked, and both of them can be isolated on a deoxyribonucleic acid fragment approximately 4,800 base pairs long. An analysis of the polypeptides synthesized in ultraviolet-irradiated cells containing these cloned genes led to the conclusion that the iia gene product is a polypeptide with a molecular weight of approximately 14,500. Insertion of transposon Tn5 into the iia gene led to a concomitant loss of the immune phenotype and the ability to produce this protein. Fractionation of ultraviolet-irradiated cells harboring a plasmid carrying the iia gene showed that the immunity protein is a component of the inner (cytoplasmic) membrane. Furthermore, the mechanism of immunity to colicin Ia appears to operate at the level of the cytoplasmic membrane. This conclusion is based on our finding that membrane vesicles prepared from colicin Ia-immune cells could be depolarized by colicins E1 and Ib but not by colicin Ia.
质粒pColIa-CA53的大肠杆菌素Ia结构（cia）基因和免疫（iia）基因已被克隆到克隆载体pBR322中。这两个基因紧密相连，它们都能在一个约4800个碱基对长的脱氧核糖核酸片段上分离出来。对含有这些克隆基因的紫外线照射细胞中合成的多肽进行分析后得出结论，iia基因产物是一种分子量约为14500的多肽。将转座子Tn5插入iia基因会导致免疫表型和产生这种蛋白质的能力同时丧失。对携带iia基因的质粒的紫外线照射细胞进行分级分离表明，免疫蛋白是内膜（细胞质膜）的一个组成部分。此外，对大肠杆菌素Ia的免疫机制似乎在细胞质膜水平起作用。这一结论基于我们的发现，即从对大肠杆菌素Ia免疫的细胞制备的膜囊泡可被大肠杆菌素E1和Ib去极化，但不能被大肠杆菌素Ia去极化。
