VOLTAGE-DEPENDENT CHANNELS FORMED BY COLICINS

Abstract

The bactericidal action of colicins K, E1, Ia and other functionally related colicins involves disruption of active transport and leakage of ions from the cell. I show that a single colicin molecule can form a voltage-dependent, relatively non-selective, ion permeable channel of a few picosiemens conductance in a planar phospholipid bilayer membrane. I suggest that the in vivo physiological effects of these colicins result from their ability to form ion-permeable channels in the bacterial inner membrane.;The voltage-dependent behavior of at least one colicin appears to be well described by a simple two state model based on the Boltzmann relation. The striking resemblance between the electrophysiology of the colicins and that of the voltage-dependent channels of nerve and muscle make the colicins an attractive model system for studying the molecular basis of ion channel gating.