Functional analysis of Pacific oyster (Crassostrea gigas) beta-thymosin: Focus on antimicrobial activity

摘要

An antimicrobial peptide, similar to 5 kDa in size, was isolated and purified in its active form from the mantle of the Pacific oyster Crassostrea gigas by C18 reversed-phase high-performance liquid chromatography. Matrix-assisted laser desorption ionisation time-of-flight analysis revealed 4656.4 Da of the purified and unreduced peptide. A comparison of the N-terminal amino acid sequence of oyster antimicrobial peptide with deduced, amino acid sequences in our local expressed sequence tag (EST) database of C. gigas (unpublished data) revealed that the oyster antimicrobial peptide sequence entirely matched the deduced amino acid sequence of an EST clone (HM-8_A04), which was highly homologous with the beta-thymosin of other species. The cDNA possessed a 126-bp open reading frame that encoded a protein of beta-amino acids. To confirm the antimicrobial activity of C gigas beta-thymosin, we overexpressed a recombinant beta-thymosin (rcgT beta) using a pET22 expression plasmid in an Escherichia coli system. The antimicrobial activity of rcgT beta was evaluated and demonstrated using a bacterial growth inhibition test in both liquid and solid cultures. (C) 2015 Elsevier Ltd. All rights reserved.