Effects of two glycine residues in positions 13 and 17 of pleurocidin on structure and bacterial cell selectivity.

Pleurocidin (Ple), a 25-residue alpha-helical antimicrobial peptide, isolated from skin mucosa of the winter flounder, shows potent bacterial cell selectivity. In this study, the effect of two glycine residues in positions 13 and 17 of Ple on structure and bacterial cell selectivity was investigated by Gly-->Ala substitution. Ala-substitution (Gly(13, 17)-->Ala, Gly13-->Ala and Gly17-->Ala) in positions 13 and 17 of Ple did not induce a significant change in antibacterial activity, but increased hemolytic activity. Both Gly(13, 17)-->Ala and Gly17-->Ala substitution did not cause a remarkable change in alpha-helical content in SDS micelles, while Gly(13, 17)-->Ala substitution caused a drastic increase in alpha-helical content. These results suggest that the hinge region from Gly13 to Gly17 of Ple is assumed to provide its conformational flexibility and bacterial cell selectivity.