Mock M, Schwartz M
J Bacteriol. 1978 Nov;136(2):700-7. doi: 10.1128/jb.136.2.700-707.1978.
As previously reported by others, more than 90% of the colicin E3 synthesized soon after induction of colicinogenic bacteria was found to be cell bound, about half of it being in a salt-extractable state at the cell surface. Evidence is presented that the colicin molecules remain preferentially bound to the cell which produced them, rather than being secreted and randomly distributed in the cell population. Secretion of colicin E3 may in fact never occur, all or most of the colicin found free in the medium perhaps being released during lysis of the producing cells long after induction. Among 19 mutant plasmids selected on the basis of their inability to produce an active colicin, only 3 were found to code for a protein which although it lacked any bactericidal activity, had the same molecular weight as wild-type colicin E3 and displayed a reaction of immunological identity with it. These three inactive colicins fail to be exported to the cell surface and seem to be blocked at some intermediate stage in the export process.
正如其他人之前所报道的，诱导产大肠杆菌素的细菌后不久合成的超过90%的大肠杆菌素E3被发现与细胞结合，其中约一半处于细胞表面可被盐提取的状态。有证据表明，大肠杆菌素分子优先与产生它们的细胞结合，而不是被分泌并随机分布在细胞群体中。事实上，大肠杆菌素E3可能从未发生分泌，在培养基中发现的游离大肠杆菌素全部或大部分可能是在诱导后很长时间产生菌细胞裂解期间释放出来的。在根据无法产生活性大肠杆菌素而选择的19个突变质粒中，仅发现3个编码一种蛋白质，该蛋白质虽然缺乏任何杀菌活性，但与野生型大肠杆菌素E3具有相同的分子量，并与其呈现免疫同一性反应。这三种无活性的大肠杆菌素无法输出到细胞表面，似乎在输出过程的某个中间阶段被阻断。
