Purification of peptides with differential cytolytic activities from the skin secretions of the Central American frog, Lithobates vaillanti (Ranidae).
Peptide-based defenses of ranid frogs from Mexico and Central America have been studied in much less detail than those from North America. Peptides belonging to the brevinin-1 (5 peptides), palustrin-2 (1 peptide), and ranatuerin-2 (3 peptides) families were isolated from norepinephrine-stimulated skin secretions of the Costa Rican frog, Lithobates vaillanti (Ranidae) and characterized structurally. Brevinin-1VLa (FLGAIAGVAAKFLPKVFCFITKKC) and brevinin-1VLc (FLPVIASVAAKVLPK VFCFITKKC) showed particularly high growth-inhibitory potency (MIC < or =3 microM) against a Gram-positive microorganism Staphylococcus aureus and the opportunistic yeast pathogen Candida albicans and potent cytolytic activity (LC(50)< or =8 microM) against both human erythrocytes and HepG2 hepatoma-derived cells. The peptides were also active against a Gram-negative microorganism Escherichia coli (MIC< or =50 microM). Substitutions in brevinin-1VLd (Lys(11) --> Asn) and brevinin-1VLe (Lys(11) --> Ser) that decrease cationicity result in loss of activity against E. coli. Ranatuerin-2VLb (GIMDTIKGAAKDLAGQLLDKLKCKITKC) showed relatively weak antimicrobial activity (MIC> or =75 microM) but selective cytolytic activity against HepG2 tumor cells (LC(50)=30 microM) compared with erythrocytes (LC(50)>200 microM). In addition, a dodecapeptide (RICYAMWIPYPC) were isolated from the secretions that were devoid of antimicrobial activity. This component contains an Ala-Met bond that constitutes the scissile bond in the selective elastase inhibitor, elafin but the peptide did not inhibit pancreatic elastase at concentrations up to 100 microM.
Conlon
J Michael
JM
Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
Raza
Haider
H
Coquet
Laurent
L
Jouenne
Thierry
T
Leprince
Jérôme
J
Vaudry
Hubert
H
King
Jay D
JD
D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D012634:Bodily Secretions / Q000737:chemistry* / Q000378:metabolism; D002176:Candida albicans / Q000187:drug effects / Q000254:growth & development; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003364:Costa Rica; D003603:Cytotoxins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005260:Female; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D008297:Male; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009638:Norepinephrine / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D011898:Ranidae / Q000378:metabolism*; D012867:Skin / Q000187:drug effects / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development
D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; D003603:Cytotoxins; D010455:Peptides; D009638:Norepinephrine