The mechanism of colicin E 1 action

Abstract

Uncouplers of oxidative phosphorylation such as cyanide carbonyl m-chlorophenylhydrazone (CCCP) foster proton (H⁺) permeability of bacterial and other membranes; counter cation movement is required for the effect of the uncoupler on proton permeability to be manifested maximally. Treatment ofEscherichia coli with colicin E 1 had little effect on the proton impermeability of the bacteria after challenge with an acid load; however, the subsequent addition of CCCP revealed that colicin E 1-treated cells became much more permeable to protons than control cells. Thus the colicin caused specific rather than generalized alterations in the membrane permeability properties, allowing the movement of some cations but not H⁺. This cation permeability was confirmed directly with studies of⁴²K leakage on treatment with colicin E 1. N,N′-dicyclohexylcarbodiimide blocked the fall in ATP levels usually associated with colicin E 1 action, but did not block the K⁺ leakage, the inhibition of protein and nucleic acid synthesis, or the lethal effect of the colicin, suggesting that reduced availability of ATP is not the cause of these colicin E 1-induced effects. The possible primary action of the colicin E 1 molecule is discussed in relation to these data.