Xenopus laevis skin secretion contains a mixture of
magainins, which are small positively charged
oligopeptides with antimicrobial activity. In this study, we show that two of these
peptides, i.e. magainin-2 and
PGLa, are much more active in
biological functions when added together than when added alone. This synergy applies for the antimicrobial activity of these
peptides, and for the toxic effects on
tumor cells. We show that this
peptide combination is also synergistic when permeabilizing
protein-free
liposomes for
glucose, when dissipating the membrane potential in
cytochrome oxidase liposomes and Escherichia coli, and, reversibly, when stimulating respiration in the
liposomes. The occurrence of synergy in these diverse systems (complex and simple) suggests that the
biological synergy results from synergy in the primary activity of the
magainin peptides, namely the permeabilization of free-energy transducing membranes, possibly by forming a multimeric transmembrane pore of mixed
peptide composition. The antimicrobial activity of X. laevis skin secretions may be greatly enhanced by the application of this binary weapon.