β-Defensin from the Asian Sea Bass, Lates calcarifer: Molecular Prediction and Phylogenetic Analysis

Antimicrobial peptides (AMPs) are an important element of the innate immune system of all living organisms and serve as a barrier that safeguards the organisms against a wide range of pathogens. Fishes are proven to be a prospective source of AMPs, and β-defensins form an important family of AMPs with potent antimicrobial, chemotactic and immunomodulatory activities. The present study reports a β-defensin AMP sequence ( Lc -BD) from the Asian sea bass, Lates calcarifer , a commercially important fish species in tropical and subtropical regions of Asia and the Pacific. A 202-bp cDNA fragment with an open reading frame encoding 63 amino acids (aa) was obtained from the mRNA of gill tissue by RT-PCR. The deduced aa sequence of Lc -BD possessed a signal and a mature peptide region with 20 and 43 aa residues, respectively. Lc -BD was characterized at the molecular level, and a molecular weight of 5.24 kDa and a net charge of +4.5 was predicted for the mature peptide. The molecular characterization of Lc -BD revealed the presence of three intramolecular disulphide bonds involving the six conserved cysteine residues in the sequence, and the phylogenetic analysis of Lc -BD showed a close relationship with β-defensins from fishes like Siniperca chuatsi , Argyrosomus regius , Trachinotus ovatus and Oplegnathus fasciatus.