Antimicrobial Properties and Membrane-Active Mechanism of a Potential α-Helical Antimicrobial Derived from Cathelicidin PMAP-36

Abstract

Antimicrobial peptides (AMPs), which present in the non-specific immune system of organism, are amongst the most promising candidates for the development of novel antimicrobials. The modification of naturally occurring AMPs based on their residue composition and distribution is a simple and effective strategy for optimization of known AMPs. In this study, a series of truncated and residue-substituted derivatives of antimicrobial peptide PMAP-36 were designed and synthesized. The 24-residue truncated peptide, GI24, displayed antimicrobial activity comparable to the mother peptide PMAP-36 with MICs ranging from 1 to 4 µM, which is lower than the MICs of bee venom melittin. Although GI24 displayed high antimicrobial activity, its hemolytic activity was much lower than melittin, suggesting that GI24 have optimal cell selectivity. In addition, the crucial site of GI24 was identified through single site-mutation. An amino acid with high hydrophobicity at position 23 played an important role in guaranteeing the high antimicrobial activity of GI24. Then, lipid vesicles and whole bacteria were employed to investigate the membrane-active mechanisms. Membrane-simulating experiments showed that GI24 interacted strongly with negatively charged phospholipids and weakly with zwitterionic phospholipids, which corresponded well with the data of its biological activities. Membrane permeabilization and flow cytometry provide the evidence that GI24 killed microbial cells by permeabilizing the cell membrane and damaging membrane integrity. GI24 resulted in greater cell morphological changes and visible pores on cell membrane as determined using scanning electron microscopy (SEM) and transmission electron microscope (TEM). Taken together, the peptide GI24 may provide a promising antimicrobial agent for therapeutic applications against the frequently-encountered bacteria.

Antimicrobial activity and membrane-active mechanism of tryptophan zipper-like β-hairpin antimicrobial peptides

“…However, in another study of H-(LARL) 3 -(LARL) n series, hemolytic activity increased, while antimicrobial activity decreased with increasing peptide chain length (Niidome et al 2005). Other work in our lab has shown that the 24-residue-truncated derivative of PMAP-36 displays antimicrobial activity comparable to the parental peptide; however, further truncation of the peptide significantly decreases its antimicrobial activity (Lv et al 2014). Based on these lines of evidence, the relationship between peptide length and antimicrobial potency is not linear, and there seems to be a threshold effect.…”

Protective effect of a novel antifungal peptide derived from human chromogranin a on the immunity of mice infected with Candida krusei

“…Antimicrobial peptides (AMPs) are currently being studied extensively to assess their use as a new class of antimycotics because they possess broad-spectrum antimicrobial activities and may possibly thwart resistance (13)(14)(15). Chromogranin A is a major soluble protein of the adrenal medullary chromaffin granules and neurons, and is conservative in mammals (16,17).…”

Antimicrobial activity, improved cell selectivity and mode of action of short PMAP-36-derived peptides against bacteria and Candida

“…Our previous study reported the potent activity of PMAP-36 and its analogs against gram-negative and gram-positive bacterial strains15, while the antifungal effects and potential mechanisms are poorly understood. Therefore, in addition to determining antibacterial activities, we measured the in vitro antifungal properties of PMAP-36 and its derivatives against Candida in the present study.…”