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ABSTRACT: To understand the structure-activity relationship of chensinin-1, a anti-microbial peptide (AMP) with an unusual structure, and to develop novel AMPs as therapeutic agents.
A series of chensinin-1 analogues were designed and synthesized by one to three replacement of glycines with leucines at the hydrophilic face of chensinin-1 or rearrangement of some of the residues in its sequence. Circular dichroism spectroscopy showed that the analogues adopted α-helical-type conformations in 50% trifluoroethanol/water but adopted β-strand-type conformations in 30 mmol l(-1) sodium dodecyl sulphate. The anti-microbial activities of the peptides against Gram-positive bacteria increased 5- to 30-fold, and these increases paralleled the increases in the peptides' hydrophobicities. Their haemolytic activities also increased. Amphipathicities had little influence on the bactericidal activity of chensinin-1. All peptides caused leakage of calcein entrapped in negatively charged liposomes although with different efficiencies. The peptides did not induce leakage of calcein from uncharged liposomes.
Peptide adopted an aperiodic structure can improve the anti-microbial potency by increasing peptide hydrophobicity. Its target is bacteria plasma membrane.
Chensinin-1 can act as a new lead molecule for the study of AMPs with atypical structures.
Journal of Applied Microbiology 06/2012; 113(3):677-85. · 2.34 Impact Factor
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ABSTRACT: Many antimicrobial peptides from amphibian skin have been purified and structurally characterized and may be developed as therapeutic agents. Here we describe the antibacterial properties and membrane interaction of chensinin-1, a cationic arginine/histidine-rich antimicrobial peptide, from the skin secretions of Rana chensinensis. The amino acid composition, sequence, and atypical structure of chensinin-1 differ from other known antimicrobial peptides from amphibian skin. Chensinin-1 exhibited selective antimicrobial activity against Gram-positive bacteria, was inactive against Gram-negative bacteria, and had no hemolytic activity on human erythrocytes. The CD spectra for chensinin-1 indicated that the peptide adopted an aperiodic structure in water and a conformational structure with 20 % β-strands, 8 % α-helices, and the remaining majority of random coils in the trifluoroethanol or SDS solutions. Time-kill kinetics against Gram-positive Bacillus cereus demonstrated that chensinin-1 was rapidly bactericidal at 2× MIC and PAE was found to be >5 h. Chensinin-1 caused rapid and large dye leakage from negatively charged model vesicles. Furthermore, membrane permeation assays on intact B. cereus indicated that chensinin-1 induced membrane depolarization in less than 1 min and followed to damage the integrity of the cytoplasmic membrane and resulted in efflux of molecules from cytoplasma. Hence, the primary target of chensinin-1 action was the cytoplasmic membrane of bacteria. Chensinin-1 was unable to overcome bacterial resistance imposed by the lipopolysaccharide leaflet, the major constituent of the outer membrane of Gram-negative bacteria. Lipopolysaccharide induced oligomerization of chensinin-1, thus preventing its translocation across the outer membrane.
Applied Microbiology and Biotechnology 05/2012; · 3.42 Impact Factor
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ABSTRACT: Temporin-1CEb shows antimicrobial activity against Gram-positive bacteria, but its therapeutic potential is limited by its haemolysis. In this study, eight temporin-1CEb analogues with altered cationicities and hydrophobicities were synthesized. Increasing cationicity and amphipathicity by substituting neutral and non-polar amino acid residues on the hydrophilic face of the α-helix by five or six lysines increased antimicrobial potency approximately 10-fold to 40-fold, although when the number of positive charges was increased from +6 to +7, the antimicrobial potency was not additionally enhanced. The substitution of an l-lysine with a d-lysine, meanwhile maintaining the net charge and the mean hydrophobicity values, had only a minor effect on its antimicrobial activity, whereas significantly led a decrease in its haemolytic activity. Of all the peptides, l-K6 has the best potential as an antimicrobial agent because its antimicrobial activity against both Gram-positive and Gram-negative bacteria is substantial, and its haemolytic activity is negligible. l-K6 adopts an α-helix in 50% trifluoroethanol/water and 30 mm SDS solutions. l-K6 killed 99.9% of E. coli and S. aureus at 4× MIC in 60 min, and its postantibiotic effect was >5 h. l-K6 affects the integrity of E. coli and S. aureus plasma membranes by rapidly inducing membrane depolarization.
Chemical Biology & Drug Design 02/2012; 79(5):653-62. · 2.28 Impact Factor
