Membrane action of colicin E1: detection by the release of carboxyfluorescein and calcein from liposomes.

Colicin E1 induces the efflux of carboxyfluorescein and calcein from liposomes whose phospholipid composition is similar to that of Escherichia coli. This colicin action takes place at protein-to-liposome ratios and within pH ranges that are physiologically meaningful. Colicin-induced permeability of carboxyfluorescein is not limited to the initial phase of colicin membrane interaction but is sustained thereafter. Colicin E1 requires negatively charged phospholipids in the liposomal membrane in order to bind and induce efflux.