科研之友
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摘要
The antimicrobial peptide chensinin-1b is a potential therapeutic agent against bacterial infection, which was derived from chensinin-1, a naturally occurring antimicrobial peptide derived from Chinese brown frog Rana chensinensis. In a membrane environment, the NMR structure of chensinin-1b showed an a-helical segment between the residues Arg8 to Arg13. To characterize the relationship between the structure and activity of chensinin-1b, the a-helical segment was truncated from the whole sequence, and the new peptides P-1 and P-3 were obtained with sequences of HWRRFWHR and WRRFWHR, respectively. The peptides showed antimicrobial activities against both Gram-positive and Gram-negative bacteria. To improve the antimicrobial activities of P-1 and P-3, histidine residues in the sequence were replaced by arginines to increase their cationicity, which enhanced the antimicrobial activities of the new analogs P-2 (RWRRFWRR) and P-4 (WRRFWRR) by approximately 4-fold. The helicity of the peptides was completely disrupted, and the peptides did not show the regular secondary structural conformations in a membrane environment. Membrane depolarization studies demonstrated that the four peptides exerted their antimicrobial effects by damaging the cytoplasmic membrane. Of these peptides, P-4 exhibited the strongest depolarization ability, which indicated a strong ability to permeabilize the outer membrane and damage the integrity of the cytoplasmic membrane. Dynamic-light-scattering experiments demonstrated that P-1, P-3 and P-4 could dissociate lipopolysaccharide (LPS) micelles, which indicated that the peptides were able to traverse the LPS leaflet. These data suggest that the peptide P-4 could be a promising molecule for the development of peptide antibiotics with short sequences.
