Abstract
Pc-pis is a novel piscidin-like antimicrobial polypeptide that was identified in Pseudosciaena crocea. Although active against most bacteria tested, Pc-pis was inactive against Aeromonas hydrophila and Pseudomonas aeruginosa. The Pc-pis analogue Pc-pis-His was designed by adding a histidine residue at the carboxyl terminal. Pc-pis-His demonstrated a more broad-spectrum and stronger antimicrobial activity against a representative set of microorganisms and more potent antiparasitic activity against Cryptocaryon irritans trophonts than Pc-pis. The stability assay revealed that Pc-pis-His was active against Staphylococcus aureus not only in acidic (pH 5.5–7.3) and relatively low concentration monovalent cation (0–160 mM NaCl) environments but also in alkaline (pH 7.5–9.5), divalent cation (1.25–160 mM MgCl2 and 1.25–40 mM CaCl2) and high concentration monovalent cation (320–2560 mM NaCl) environments, which indicates that the added histidine residue conferred better salt-, acid- and alkali-tolerance to Pc-pis-His. Pc-pis-His also possessed the desired heat-tolerance, which was reflected by the antimicrobial activity of the peptide after being boiled for 10–60 minutes. Hemolytic activity analysis revealed that Pc-pis-His at concentrations up to 6 µM exhibited no hemolysis against human erythrocytes, with 6 µM being a concentration that is highly active against most of the microorganisms tested, although the hemolytic activity of Pc-pis-His was enhanced compared to Pc-pis. These results provide a unique, reasonable basis for designing novel piscidins with potent, broad-spectrum and stable antimicrobial activity and new insight into the future development of piscidins as potential therapeutic agents against microbial and external protozoan parasite infections.
Highlights
With the development of marine aquaculture, various infectious diseases can inflict significant economic losses on the aquaculture industry, such as marine cryptocaryonosis, which results in as much as 75% and 50% mortality for Pseudosciaena crocea and juvenile Epinephelus tauvina, respectively [1,2]
The added histidine residue was located in the middle of the hydrophobic phase (Figure 1B), which tends to disrupt the amphipathic a-helix and lowers its amphipathicity
Analysis of the amino acid sequences showed that Pc-pis-His (GRAVY = 0.630, charge = 6 and pI = 12.00) had a lower grand average of hydropathicity index (GRAVY), a higher charge and an equal theoretical pI compared to Pc-pis (GRAVY = 0.805, charge = 5 and pI = 12.00)
Summary
With the development of marine aquaculture, various infectious diseases can inflict significant economic losses on the aquaculture industry, such as marine cryptocaryonosis (white spot disease), which results in as much as 75% and 50% mortality for Pseudosciaena crocea and juvenile Epinephelus tauvina, respectively [1,2]. Some other peptides have the potential to be improved in antimicrobial activity, antiparasitic activity or other respects [1,7,8]. Some AMPs, such as Pis-1, IsCT and HP (2–20) analogues, exhibited increased desirable biological activity after the incorporation of some amino acids into the various AMPs [10,11,13]. These studies demonstrate that the creation of AMP analogues with an extensive use range is a hopeful strategy for the development of potential therapeutic drugs
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