Conformational analysis and cytotoxic activities of the frog skin host-defense peptide, hymenochirin-1Pa

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2014-11, Vol.61, p.114-121
• Main Authors: Serra, Ilaria, Scorciapino, Mariano A., Manzo, Giorgia, Casu, Mariano, Rinaldi, Andrea C., Attoub, Samir, Mechkarska, Milena, Conlon, J. Michael
• Format: Article
• Language: English
• Subjects: 3D structure; Amphibian Proteins - chemistry; Amphibian Proteins - genetics; Amphibian Proteins - pharmacology; Animals; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Anticancer activity; Antiinfectives and antibacterials; Antimicrobial Cationic Peptides - chemistry; Antimicrobial Cationic Peptides - genetics; Antimicrobial Cationic Peptides - pharmacology; Antimicrobial peptide; Bacteria; Cell Line, Tumor; Cytotoxins - chemistry; Cytotoxins - pharmacology; Erythrocytes; Erythrocytes - cytology; Erythrocytes - metabolism; Frogs; Gram-Positive Bacteria - growth & development; Hemolysis - drug effects; Human; Humans; Linearity; NMR; Peptides; Pipidae; Protein Structure, Secondary; Residues; Skin - chemistry; Structure-Activity Relationship
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/j.peptides.2014.08.017

•The 3D structure of the frog-skin peptide hymenochirin-1Pa was determined.•A central GXXXG motif is responsible for the kinked helical folding.•The anti-bacterial, anti-cancer and hemolytic activity was assessed.•The biologic activities of analogs with increased cationicity was compared. Hymenochirin-1Pa (LKLSPKTKDTLKKVLKGAIKGAIAIASMA-NH2) is a host-defense peptide first isolated from skin secretions of the frog Pseudhymenochirus merlini (Pipidae). A nuclear magnetic resonance structural investigation demonstrates that the peptide has a random coil conformation in water but, in the membrane-mimetic solvent 50% (v/v) trifluoroethanol–water adopts a well-defined conformation characterized by two α-helical domains from residues K6 to G17 and from G21 to M28, with the N-terminal region unfolded. The presence of a GXXXG domain, the most common structural motif found at the interface between interacting trans-membrane helices, between residues 17 and 21, introduces a kink corresponding to a deviation from linearity of 93±31°. Hymenochirin-1Pa shows broad spectrum anti-bacterial activity, including high potency against multidrug-resistant clinical isolates of Staphylococcus aureus, Acinetobacter baumannii, and Stenotrophomonas maltophilia. The peptide also shows high cytotoxic potency against human non-small lung adenocarcinoma A549 cells, breast adenocarcinoma MDA-MB-231 cells, and colorectal adenocarcinoma HT-29 cells but its therapeutic potential as an anti-cancer agent is limited by moderate hemolytic activity against human erythrocytes and lack of selectivity for tumor cells. Increasing cationicity of the peptide by substituting the Asp9 residue by either l-Lys (K) or d-Lys (k) has relatively minor effects on antimicrobial and anti-tumor potencies but the [D9k] analog is non-hemolytic LC50>400μM. Thus, [D9k]hymenochirin-1Pa may serve as a template for the design of non-toxic antimicrobial agents for use against multidrug-resistant pathogenic bacteria.