Identification and Bioinformatics Analysis of β-Defensin Gene Family in Huangsha Soft-Shelled Turtle

Abstract

β-defensin is a small cationic antimicrobial peptide rich in cysteine, which plays an important role in innate immunity of the living organism. In this study, the β-defensin genes of Huangsha soft- shelled turtle (Hs-BDs) family were identified based on transcriptome database of Huangsha soft- shelled turtle and PCR validation, and the physicochemical properties of protein, protein structure and evolutionary relationship were also analyzed. The results showed that a total of 18 members of Hs-BDs family with complete coding regions were identified. The number of amino acid residues of these Hs-BDs proteins ranged from 59 to 94, the molecular weight ranged from 6759.13 to 10,731.32 Da, and the isoelectric point ranged from 8.82 to 10.45. The 18 members of Hs-BDs family were divided into four subgroups (Class I~IV) according to the phylogenetic tree analysis. Some Hs-BDs were randomly selected for protein structure analysis and the results showed that the secondary structures of Hs-BDs preprotein are mainly composed of α-helix, β-sheet and random coil. Six conserved cysteine residues were linked to form three intramolecular disulfide bonds in the form of Cys1-Cys5, Cys2-Cys4 and Cys3-Cys6, respectively. The results of this study can provide basic data for further research on the detailed functions of β-defensin gene family and the development of antimicrobial peptides.