Molecular characterization of a mollusk chicken-type lysozyme gene from Haliotis discus hannai Ino, and the antimicrobial activity of its recombinant protein

Abstract

A chicken-type lysozyme was obtained and characterized from the abalone Haliotis discus hannai Ino (HdLysC). The full-length cDNA of HdLysC was 586 bp, and it contained an open reading frame of 441 bp, encoding a 147-amino acid protein with a calculated molecular mass of 15.64 kDa and an isoelectric point of 4.87. The amino acid sequence of HdLysC possessed all conserved features critical for the fundamental structure and function of c-type lysozymes, including the two catalytic residues, Glu54 and Asp70. The genomic length of HdLysC was 2865 bp, with four exons interrupted by three introns. The genomic structure of HdLysC was more similar to vertebrates than invertebrates. Many putative transcription factor binding sites involved in the immune system and cancer were found in the promoter region of HdLysC. Quantitative real-time RT-PCR detected HdLysC expression in all examined tissues, as well as in an expression profile of abalone gills challenged with bacteria Vibrio anguillarum. HdLysC transcripts were found to be most abundantly expressed in mantles, and weakly expressed in hemocytes, and increased expression of HdLysC also observed after bacterial stimulation. HdLysC was expressed in Escherichia coli, and the recombinant protein showed bacteriolytic activity against both Gram-positive and Gram-negative bacteria. Of the Vibrio species tested, more effective activity was detected against V. anguillarum.