Effects of amino acid deletion and substitution on the chemical properties, biological activities of the frog peptide palustrin-OG1.

Palustrin-OG1 (OG1) is a host defense peptide isolated from the frog Odorrana grahami. In this study, we analyzed the chemical properties, antimicrobial activities and cytotoxicities of OG1 and its derivatives to identify the most promising peptide as an antimicrobial agent. By increasing the net positive charge, amphipathicity and decreasing the mean hydrophobicity of OG1, the derivative named as OG2 exerted higher antimicrobial activity against bacteria but lower cytotoxicity against both porcine erythrocytes and peripheral blood mononuclear cells than did OG1 (P<0.01). After substitution of Cys residues of OG2 by Ala or Trp residues, two derivatives named as OG2A and OG2W were less effective against bacteria and induced greater hemolysis than did OG2, indicating the importance of Cys residues. The substitution of the C-terminal Thr of OG2 resulted OG2N, which decreased the cytotoxicity and improved killing kinetics against gram-positive bacteria by the rapid damage of cell wall and membrane.