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 beta-defensins form an important family of AMPs with potent antimicrobial, chemotactic and immunomodulatory activities. The present study reports a beta-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 beta-defensins from fishes like Siniperca chuatsi, Argyrosomus regius, Trachinotus ovatus and Oplegnathus fasciatus.

Automated summary

Antimicrobial peptides (AMPs) are crucial components of the innate immune system in all living organisms, with fishes such as the Asian sea bass being a potential source of AMPs, particularly from beta-defensins known for their antimicrobial and immunomodulatory activities. The molecular characterization of a beta-defensin AMP sequence (Lc-BD) from the Asian sea bass revealed key features such as the presence of intramolecular disulphide bonds and a close phylogenetic relationship with beta-defensins from other fish species.