Solution Structure and Cell Selectivity of Piscidin 1 and Its Analogues^,

Abstract

Piscidin 1 (Pis-1) is a novel cytotoxic peptide with a cationic alpha-helical structure that was isolated from the mast cells of hybrid striped bass [Silphaduang, U., and Noga, E. J. (2001) Nature 414, 268-269]. Pis-1 is not selective for bacterial versus mammalian cells. In the present study, to develop novel antibiotic peptides with selectivity for bacterial cells, we examined the effect of substituting two glycine residues, Gly8 and Gly13, with Ala or Pro on this peptide's structure and biological activities. The bacterial cell selectivity of the peptides decreased in the following order: Gly-->Pro analogues > Gly-->Pro/Ala analogues > Pis-1 > Gly-->Ala analogues. The antimicrobial and hemolytic activities and abilities to permeabilize the model phospholipid membranes were higher for Pis-1 with Gly or Pro at position 8 than for its counterparts with either Gly or Pro at position 13. We determined the tertiary structure of Pis-1 and its analogues in the presence of SDS micelles by NMR spectroscopy. We found that Pis-1 has an alpha-helical structure from Phe2 to Thr21. Also, Pis-1 AA (Gly8, Gly13-->Ala8, Ala13) with higher antibacterial and hemolytic activity than Pis-1 has a stable alpha-helical structure from Phe2 to Thr21. Pis-1 PG (Gly-->Pro8) with bacterial cell selectivity has a hinge structure at Pro8, which provides flexibility in piscidin, followed by a three-turn helix from Val10 to Gly22 in the C-terminal region. Taken together, our results demonstrate that the conformational flexibility provided by introduction of a Pro at position 8, coupled with the primary anchoring of phenylalanines and histidines in the N-terminus to the cell membrane and the optimal length of the C-terminal amphipathic alpha-helix, are the critical factors that confer antibacterial activity and bacterial cell selectivity to Pis-1 PG. Pis-1 PG may be a good candidate for the development of a new drug with potent antibacterial activity but without cytotoxicity.

The Combination Effect of Korean Red Ginseng Saponins with Kanamycin and Cefotaxime against Methicillin-Resistant Staphylococcus aureus

“…We employed negatively charged LUVs composed of 1 : 1 (w/w) PC/PG lipids used for mimicking the major components of the cell membrane of bacteria. 17,18) The percentage of calcein leakage 2 min after exposure to ginsenosides or nisin was used to assess the ability to permeabilize the membrane. The results showed that 100 mg/ml of ginsenosides (at the MIC) induced 52.1% leakage of calcein from negatively charged vesicles, whereas 40 mg/ml of nisin (at the MIC) only induced approximately 10% of leakage of the dye (Fig.…”

An Overview of the Immunological Defenses in Fish Skin

“…Examples of piscidins are also dicentracin from the European bass (Dicentrarchus labrax) [165], chrysophsins from red sea bream (Chrysophrys major) [166], and epinecidin from the orange-spotted grouper (Epinephelus coioides) [167]. Lee et al [168] determined the solution structure of piscidin-1, and then piscidin-2 was found to cause cell membrane damage to three fungal strains known to cause infections in humans [169]. Piscidin-immunoreactive cells were most common at sites of pathogen entry (including the skin, gill, and gastrointestinal tract), and immunopositive cells were usually most consistent with mast cells [151].…”

Simulations of Membrane-Disrupting Peptides II: AMP Piscidin 1 Favors Surface Defects over Pores

“…The peptide exhibits antimicrobial activity against methicillin-resistant Staphylococcus aureus (24), viruses such as HIV-1 (25), fungi (26), and cancer cells (27). Like other AMPs, piscidin induces dye leakage in model membranes and membrane disruption is proposed to be its primary mechanism of action against bacteria (28,29). The surfacebound structures of p1 were determined independently by ssNMR and all-atom molecular dynamics (MD) in two different bacterial cell mimics (30).…”