[Isolation, identification and bioactivity characterization of goose avian beta-defensin 3]

The objective of the study was to clone avian beta-defensin (AvBD) 3 gene from goose tissues, express the recombinant AvBD3 protein in Escherichia coli, and determine its antimicrobial activity. The mRNA of goose AvBD3 was cloned from spleen and bursa of Fabricius of the gooses by RT-PCR. The sequence analysis showed that the genefragment of AvBD3 contained 182 bp, and encoded 60 amino acids. Homology analysis showed that goose AvBD3 shared the highest percentage of amino acid homology (100%) with chicken AvBD3. The cDNA of goose AvBD3 was sub-cloned into BamH I and Sal I sites of pGEX-6p-1 vector to construct recombinant plasmid pGEX-goose AvBD3. The recombinant plasmid was transformed into E. coli BL21 and the bacteria was induced with IPTG It was demonstrated by SDS-PAGE that a 31 kDa protein which was equal to goose AvBD3 protein in molecular weight was highly expressed. The purified recombinant goose AvBD3 exhibited extensive antimicrobial activity against twelve bacteria strains, including Gram-positive and Gram-negative investigated. At high salt ions conditions, antimicrobial activity of recombinant goose AvBD3 protein against both Staphylococcus aureus and Pasteurella multocida decreased significantly. In addition, hemolysis activity of the recombinant protein was extremely low, and the recombinant protein remained antimicrobial activity under different pH values.