title: Antimicrobial and cytolytic properties of the frog skin peptide, kassinatuerin-1 and its L- and D-lysine-substituted derivatives.
abstract: Kassinatuerin-1, a 21-amino-acid C-terminally alpha-amidated peptide first isolated from the skin of the African frog Kassina senegalensis, adopts an amphipathic alpha-helical conformation in a membrane-mimetic solvent (50% trifluoroethanol) and shows broad-spectrum antimicrobial activity. However, its therapeutic potential is limited by its relatively high cytolytic activity against mammalian cells. The antimicrobial and cytolytic properties of a peptide are determined by an interaction between cationicity, hydrophobicity, alpha-helicity and amphipathicity. Replacement of the C-terminal alpha-amide group in kassinatuerin-1 by carboxylic acid decreased both cationicity and alpha-helicity, resulting in an analog with decreased potency against Escherichia coli (4-fold) and Staphylococcus aureus (16-fold). Low cytolytic activities against human erythrocytes (LD50>400 microM) and L929 fibroblasts (LD50=105 microM) were also observed. Increasing cationicity, while maintaining amphipathic alpha-helical character, by progressively substituting Gly7, Ser18, and Asp19 on the hydrophilic face of the alpha-helix with L-lysine, increased antimicrobial potency against S. aureus and Candida albicans (up to 4-fold) but also increased hemolytic and cytolytic activities. In contrast, analogs with d-lysine at positions 7, 18 and 19 retained activity against Gram-negative bacteria but displayed reduced hemolytic and cytolytic activities. For example, the carboxylic acid derivative of [D-Lys7, D-Lys18, D-Lys19]kassinatuerin-1 was active (minimum inhibitory concentration (MIC)=6-12.5 microM) against a range of strongly antibiotic-resistant strains of E. coli but showed no detectable hemolytic activity at 400 microM and was 4-fold less cytolyic than kassinatuerin-1. However, the reduction in alpha-helicity produced by the D-amino acid substitutions resulted in analogs with reduced potencies against Gram-positive bacteria and against C. albicans.
authors.affiliation: Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, P.O. Box 17666, Al Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
authors.forename: Bency
authors.initials: B
authors.lastname: Abraham
authors.forename: Sehamuddin
authors.initials: S
authors.lastname: Galadari
authors.forename: Floyd C
authors.initials: FC
authors.lastname: Knoop
authors.forename: Agnes
authors.initials: A
authors.lastname: Sonnevend
authors.forename: Tibor
authors.initials: T
authors.lastname: Pál
mesh_terms: D019943:Amino Acid Substitution; D029845:Amphibian Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D001001:Anura; D002176:Candida albicans / Q000187:drug effects / Q000254:growth & development; D002460:Cell Line; D004912:Erythrocytes / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005347:Fibroblasts / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D017433:Protein Structure, Secondary; D012867:Skin / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship
chemical_list: D029845:Amphibian Proteins; D000890:Anti-Infective Agents; D010455:Peptides; C404848:kassinatuerin-1