Antimicrobial function of SHβAP, a novel hemoglobin β chain-related antimicrobial peptide, isolated from the liver of skipjack tuna, Katsuwonus pelamis

A 23 kDa of antimicrobial peptide was purified from an acidified liver extract of skipjack tuna, Katsuwonus pelamis, by preparative acid-urea polyacrylamide gel electrophoresis and C-18 reversed-phase HPLC. A comparison of the amino acid sequence of the purified peptide with those of other known polypeptides revealed high homology with the C-terminus of hemoglobin beta-chain; thus, this peptide was designated as the Skipjack Hemoglobin beta chain-related Antimicrobial Peptide (SH beta AP). SH beta AP showed potent antimicrobial activity against Gram-positive bacteria, such as Bacillus subtilis, Staphylococcus aureus, and Streptococcus iniae (minimal effective concentrations [MECs], 6.5-57.0 mu g/mL), Gram-negative bacteria, such as Escherichia coli D31, Pseudomonas aeruginosa, Salmonella enterica, Shigella sonnei, and two Vibrio parahaemolyticus species (MECs, 2.0-19.0 mu g/mL), and against Candida albicans (MEC; 12.0 mu g/mL) without significant hemolytic activity. Antimicrobial activity of this peptide was heatstable and pH resistant but is sensitive to proteases and salt. SH beta AP did not show membrane permeabilization and killing ability. The secondary structural prediction and the homology modeling expected that this peptide formed an amphipathic alpha-helical structure. This is the first report the purification of a novel antimicrobial peptide related to the C-terminus of hemoglobin beta-chain from marine fish. (C) 2014 Elsevier Ltd. All rights reserved.