A synthetic peptide corresponding to the C‐terminal 25 residues of phage MS2 coded lysis protein dissipates the protonmotive force in Escherichia coli membrane vesicles by generating hydrophilic pores.

The RNA phage MS2 encodes a protein, 75 amino acids long, that is necessary and sufficient for lysis of the host cell. DNA deletion analysis has shown that the lytic activity is confined to the C‐terminal half of the protein. We have examined the effects of a synthetic peptide, covering the C‐terminal 25 amino acids of the lysis protein, on the electrochemical potential, generated in Escherichia coli membrane vesicles and in liposomes reconstituted with cytochrome c oxidase. In all cases the peptide dissipates the electrochemical potential. The peptide also induces the release of carboxyfluorescein (376 daltons), but not of inuline (5500 daltons), from protein‐free liposomes. The phenomena are observed at a lipid to peptide molar ratio of approximately 100:1. The possible connection between the dissipation of the proton‐motive force and bacteriolysis is discussed.