Energy Coupling Factor as Target of Colicin K: Characterization of a Colicin K-Insensitive ecf Mutant of Escherichia coli

Abstract

We isolated a colicin K-insensitive energy uncoupled mutant of Escherichia coli . This mutant was presumed to be an ecf mutant as evidenced by its similarity to a known ecf mutant (M. A. Lieberman and J.-S. Hong, 1974) with respect to the mutational site, reversion pattern, and defects in transport and growth. The mutation conferring the colicin K-insensitivity resided in the ecf gene as the majority of the secondary mutations overcoming the ecf phenotype reverted the colicin K-insensitive phenotype to colicin K-sensitive. The insensitivity of the mutant to colicin K was not due to either a defect in adsorption or to a lack of the energized membrane state. The defect was most probably due to the inability of colicin K molecules to interact with their target. Our previous studies concerning the role of the ecf gene product in energy coupling to active transport and oxidative phosphorylation support the contention that the ECF protein is itself the direct target of colicin K.

Escherichia coli K-12 tolZ mutants tolerant to colicins E2, E3, D, Ia, and Ib: defect in generation of the electrochemical proton gradient

“…min, respectively. The ecfA (16) and ecfB (28) mutants are unable to transport proline and thiomethyl-,3-D-galactoside, like the tolZ mutant. All of these mutants except tolZ are sensitive to colicins E2 and E3.…”

“…Several colicin-tolerant mutants of E. coli, which have a defect in growing on nonfermentable carbon sources, were reported, and their mutation loci were determined as follows: tolI (1,8), tolerant to colicins Ia and Ib, 0 min; and efcA (1,16) and ecfB (1,28) tolerant to colicin K, 65 and 88 I-I-I-66 68 74 1176 78 80 82 841 min I F141 |Z __ _ II F140 Hfr KL14 PK3 KL228 FIG. 4.…”

“…This may suggest that the tolZ mutation is recessive. ADDENDUM Some colicin K used previously (16,18,28) may be colicin A, judging from reference 24.…”