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

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 softshelled turtle (Hs-BDs) family were identified based on transcriptome database of Huangsha softshelled 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.