title: Role of C-terminal heptapeptide in pore-forming activity of antimicrobial agent, gaegurin 4.
abstract: Gaegurin 4 (GGN4) is an antimicrobial peptide of 37 amino acids isolated from the skin of a frog, Rana rugosa. GGN4 has a disulfide bond between the residues 31 and 37, which is highly conserved among the antimicrobial peptides isolated from skin of the genus, Rana. However, the role of this C-terminal heptapeptide motif is not well understood. In this work, we compared the membrane effects of the full-length GGN4 (C37) and GGN4 1-30 (C30), which is devoid of the C-terminal seven amino acids to elucidate the function of the C-terminal motif. C37 induced significantly larger membrane conductance (>10x) in the model lipid bilayers formed with acidic and neutral phospholipids and larger K+ efflux from gram-positive (>30x) and gram-negative bacteria. However, the pores induced by C37 and C30 were not different in their permeability to K+ over Cl- (permeability ratio of K+ to Cl- = 4.8-7.1). In addition, the pore-forming effect of C37 or C30 in acidic membranes was not different from that in neutral membranes. Furthermore, C37-induced K+ efflux was not significantly decreased by the reducing agent, dithiothreitol. The results indicate that C-terminal heptapeptide sequence plays an important role in maintaining the high pore-forming activity of GGN4, but does not participate in forming GGN4-induced pore structure. The disulfide bond in this region does not appear critical for such high ionophoric activity of GGN4.
authors.affiliation: Department of Veterinary Pharmacology, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Korea.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: S S
authors.initials: SS
authors.lastname: Kim
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: B J
authors.initials: BJ
authors.lastname: Lee
authors.forename: P D
authors.initials: PD
authors.lastname: Ryu
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D002713:Chlorine / Q000737:chemistry; D004594:Electrophysiology; D004926:Escherichia coli / Q000378:metabolism; D007477:Ions; D007700:Kinetics; D008051:Lipid Bilayers; D010455:Peptides / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry; D011498:Protein Precursors / Q000737:chemistry* / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011898:Ranidae; D013997:Time Factors
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D002412:Cations; D007477:Ions; D008051:Lipid Bilayers; D010455:Peptides; D011498:Protein Precursors; C096396:gaegurin 4; D002713:Chlorine; D011188:Potassium