Structure and Mechanism of Action of the Antimicrobial Peptide Piscidin

Abstract

Piscidin, an antibacterial peptide isolated from the mast cells of striped bass, has potent antimicrobial activity against a broad spectrum of pathogens in vitro. We investigated the mechanism of action of this 22-residue cationic peptide by carrying out structural studies and electrophysiological experiments in lipid bilayers. Circular dichroism experiments showed that piscidin was unstructured in water but had a high alpha-helix content in dodecylphosphocholine (DPC) micelles. 1H NMR data in water and TFE confirmed these results and demonstrated that the segment of residues 8-17 adopted an alpha-helical structure in a micellar environment. This molecule has a marked amphipathic character, due to well-defined hydrophobic and hydrophilic sectors. This structure is similar to those determined for other cationic peptides involved in permeabilization of the bacterial membrane. Multichannel experiments with piscidin incorporated into azolectin planar bilayers gave reproducible I-V curves at various peptide concentrations and unambiguously showed that this peptide permeabilized the membrane. This pore forming activity was confirmed by single-channel experiments, with well-defined ion channels obtained at different voltages. The characteristics of the ion channels (voltage dependence, only one or two states of conductance) clearly suggest that piscidin is more likely to permeabilize the membrane by toroidal pore formation rather than via the "barrel-stave" mechanism.

Combined Bioinformatic and Rational Design Approach To Develop Antimicrobial Peptides against Mycobacterium tuberculosis

“…3B). In phosphate buffer, B1, B2, and B3 produced far-UV CD spectra associated with ␣-helical peptides, with ⍜ minima at 222 nm and 205 nm in addition to an apparent maximum at 190 nm (33,34). B4, the "scrambled-sequence" control peptide, maintained a spectrum more closely aligned with a random coil/extended structure with a single minimum at 200 nm (Fig.…”

Fungicidal Effect of Piscidin on Candida albicans: Pore Formation in Lipid Vesicles and Activity in Fungal Membranes

“…25,26) In the bacterial system, piscidins have antibacterial activities, which are possibly due to their ability to permeabilize bacterial membranes. 15,27) To investigate the membranepermeabilizing ability of piscidins, we measured the release of the fluorescent marker, calcein, from liposomes of different compositions. We employed neutral charged LUVs composed of 10 : 1 (w/w) PC/cholesterol lipids used for mimicking the major components of the cell membrane of human erythrocytes, and negatively charged LUVs composed of 3 : 1 (w/w) PC/PS to mimic microbial cells.…”

“…13,14) Also, its mechanism of action against bacteria was defined as that piscidin is more likely to permeabilize the membrane by toroidal pore formation rather than via the "barrel-stave" mechanism. 15) However, their exact mode of fungicidal action remains unknown.…”

An Overview of the Immunological Defenses in Fish Skin

“…This study was the first one which identified in rodlet cells a host-associated chemical biomarker [157]. All piscidins show broad-spectrum antimicrobial activity, probably killing cells via toroidal-pore formation [151,170,171]. Although attractive as potential candidates for topical application use because of their activity at high salt concentrations [172], the disadvantage of piscidins in this regard is their haemolytic and cytotoxic properties [173].…”