Nogami T, Mizushima S
J Bacteriol. 1983 Oct;156(1):402-8. doi: 10.1128/jb.156.1.402-408.1983.
Escherichia coli cells lacking the OmpF and OmpC proteins, porin proteins of the outer membrane, are often unstable and easily revert to strains which either have regained one or both of these proteins or contain a new outer membrane protein. The structural importance of porin proteins in the cell surface was studied in the present work. Tris-hydrochloride buffer at a concentration of 120 mM caused deformation of the cell surface of a strain lacking these porins; the undulated appearance of the negatively stained cell surface changed to a smooth and expanded form. The Tris-induced deformation was seldom observed with either the wild-type strain or a pseudorevertant that possessed the OmpF protein. The role of the OmpF protein in stabilizing the cell surface against Tris treatment could be slightly taken over by the LamB protein, which shares a number of unique properties with the former proteins. The deformation of the cell surface by Tris-hydrochloride buffer was accompanied by a loss of viability, the lethal damage being especially significant when the cells lacked porins. Upon induction with maltose, cells with the undulated appearance could absorb lambda phages, whereas the deformed cells could not. These results suggest that the instability of cells lacking porins is primarily due to a structural defect of the outer membrane.
缺乏外膜孔蛋白OmpF和OmpC蛋白的大肠杆菌细胞通常不稳定，容易回复到重新获得这两种蛋白中的一种或两种或者含有一种新的外膜蛋白的菌株。在本研究中对孔蛋白在细胞表面的结构重要性进行了研究。浓度为120 mM的 Tris-盐酸缓冲液会导致缺乏这些孔蛋白的菌株的细胞表面变形；经负染的细胞表面起伏不平的外观变为光滑且膨胀的形态。野生型菌株或具有OmpF蛋白的假回复株很少观察到Tris诱导的变形。LamB蛋白与前几种蛋白具有许多独特特性，它可以略微替代OmpF蛋白在稳定细胞表面抵抗Tris处理方面的作用。Tris-盐酸缓冲液导致的细胞表面变形伴随着活力丧失，当细胞缺乏孔蛋白时，致死损伤尤为显著。用麦芽糖诱导后，外观起伏不平的细胞可以吸收λ噬菌体，而变形的细胞则不能。这些结果表明，缺乏孔蛋白的细胞的不稳定性主要是由于外膜的结构缺陷。
