A macin identified from Venerupis philippinarum: Investigation on antibacterial activities and action mode.

In the present study, a macin was cloned and characterized from clam Venerupis philippinarum (designed as VpMacin). The full-length cDNA of VpMacin was of 579 bp, encoding a peptide of 87 amino acids with the predicted molecular weight of 9.7 kDa. Analysis of the conserved domain suggested that VpMacin was a new member of the macin family. In non-stimulated clams, VpMacin transcripts exhibited different tissue expression pattern, and highly expressed in the tissues of gills and hepatopancreas. Generally, the temporal expression of VpMacin transcripts was significantly induced in hemocytes of clams post Vibrio anguillarum challenge. Moreover, the recombinant VpMacin protein (rVpMacin) showed obvious antimicrobial activities against Gram-positive and Gram-negative bacteria. After incubated with 40 µM rVpMacin, all detected Escherichia coli could be killed within 60 min. Membrane integrity analysis revealed that rVpMacin could increase the membrane permeability of bacteria and then resulted in cell death. Overall, our results suggested that VpMacin had an important function in host defense against invasive pathogens.