Mutant of Escherichia coli defective in response to colicin K and in active transport

Abstract

A mutant of E. coli was isolated that grows poorly on succinate and exhibits a markedly reduced sensitivity to colicin K. This mutant is also deficient in the respiration-linked transport of proline and thiomethyl-.beta.-D-galactoside but appears normal for the ATP-dependent transport of glutamine and arginine. A temperature-conditional revertant of the mutant grows on succinate and is sensitive to colicin K at 27.degree. C, but fails to grow on succinate and is insensitive to colicin K at 42.degree. C. Proline transport in the temperature-conditional revertant is reduced at 42.degree. C when either glucose or succinate is used as energy source. Glutamine transport is normal at 42.degree. C with glucose as energy source, but is reduced with succinate, although not to the same extent as is proline transport. The lack of growth on succinate and the deficiencies in transport at 42.degree. C are not due to a temperature-dependent lesion in either the electron transport chain or in Ca2+, Mg2+-activated ATPase activity. Membrane vesicles prepared from the temperature-conditional revertant are impaired in proline transport at both 27 and 42.degree. C. The existence in the cytoplasmic membrane of E. coli of a component, presumably protein, that is required for colicin K action and that functions in respiration-linked and, to a lesser degree, in ATP-dependent active transport systems, is suggested. This protein may serve as the primary target of colicin K action.