REQUIREMENTS FOR ANTIBACTERIAL AND HEMOLYTIC ACTIVITIES IN THE BOVINENEUTROPHIL-DERIVED 13-RESIDUE PEPTIDE INDOLICIDIN

The antimicrobial and hemolytic activities of the 13-residue peptide i ndolicidin (ILPWKWPWWPWRR-NH2), present in bovine neutrophils, and its analogs hare been determined with a view to gaining insight into the structural roles of tryptophan and proline, Peptides where proline was replaced by alanine and tryptophan by phenylalanine showed antibacter ial activities comparable to that of indolicidin, The peptides do not exhibit a strong propensity to occur in either helical or beta-sheet c onformation, The peptides also do not appear to exert their activity b y permeabilizing the bacterial plasma membrane unlike other endogenous antibacterial peptides, The presence of tryptophan appears to be esse ntial for hemolytic activity as the phenylalanine analog does not exhi bit any hemolytic activity.