DELTA-TOXIN, UNLIKE MELITTIN, HAS ONLY HEMOLYTIC-ACTIVITY AND NO ANTIMICROBIAL ACTIVITY - RATIONALIZATION OF THIS SPECIFIC BIOLOGICAL-ACTIVITY

The antimicrobial activity of a synthetic peptide corresponding to del ta-hemolysin had been examined. The peptide did not exhibit antimicrob ial activity against gram negative and gram positive micro-organisms u nlike other hemolytic peptides like melittin. This lack of antibacteri al activity arises due to the inability of delta-hemolysin to perturb the negatively charged bacterial cell surface and permeabilize the bac terial plasma membrane. However, the red blood cell surface has a stru cture considerably different from bacteria and does not act as a barri er to molecules reaching the lipid membrane. Hence delta-toxin can lys e erythrocytes. Thus, the specificity in biological activity has been rationalized in terms of differences in the interaction of the toxin w ith the bacterial and red blood cell surfaces.