Molecular Characterization of a Novel Cathepsin B from Striped Murrel Channa striatus: Bioinformatics Analysis, Gene Expression, Synthesis of Peptide and Antimicrobial Property

In this study, we have reported a full length cDNA of cathepsin B identified from the constructed cDNA library of snakehead murrel Channa striatus by genome sequence FLX technology. The identified full length C. striatus cathepsin B (CsCath B) is 1486 base pairs (bp) long which contains 990 bp open reading frame (ORF). The ORF region encodes 330 amino acids with a molecular mass of 36 k Da. This amino acid sequence contains three thiol protease motifs at 101-112, 275-285 and 292-311 with their respective active sites viz., Cys(197), His(277) and Asp(297). CsCath B exhibited the maximum similarity (87%) with Cath B from mangrove red snapper, Lutjanus argentimaculatus. Phylogenetically, CsCath B is clustered together with the fish groups belonging to perciformes. A predicted 3D model of CsCath B revealed 11 alpha-helix and 10 beta-strands. CsCath B contains higher percentage (10%) of coils due to the presence of many glycine residues (36 residues). The highest gene expression (P<0.05) was noticed in liver. Further, the expression was induced with fungal (Aphanomyces invadans) and bacterial (Aeromonas hydrophila) infections. The predicted antimicrobial region of CsCath B was synthesized to study its antimicrobial property. The peptide exhibited the antimicrobial activity towards Gram negative and Gram positive bacteria. The overall results indicate that CsCath B is a potential molecule for further studies on murrel defense mechanism.