δ-toxin, unlike melittin, has only hemolytic activity and no antimicrobial activity: rationalization of this specific biological activity

Abstract

The antimicrobial activity of a synthetic peptide corresponding to δ-hemolysin had been examined. The peptide did not exhibit antimicrobial activity against gram negative and gram positive micro-organisms unlike other hemolytic peptides like melittin. This lack of antibacterial activity arises due to the inability of δ-hemolysin to perturb the negatively charged bacterial cell surface and permeabilize the bacterial plasma membrane. However, the red blood cell surface has a structure considerably different from bacteria, and does not act as a barrier to molecules reaching the lipid membrane. Hence δ-toxin can lyse erythrocytes. Thus, the specificity in biological activity has been rationalized in terms of differences, in the interaction of the toxin with the bacterial and red blood cell surfaces.