Identification and characterization of a serine protease from Bacillus licheniformis W10: A potential antifungal agent.

Bacillus licheniformis W10 is a strain of biocontrol bacteria that was obtained from plant rhizosphere screening. In this study, we purified, identified, and carried out bioinformatics analysis of the W10 antifungal protein from Bacillus licheniformis. Mass spectrometry analysis was carried out by passing the antifungal protein through a high-resolution time-of-flight mass spectrometer. Mascot searches of the tandem mass spectrometry data identified this antifungal protein as a serine protease, and the 1347 bp gene encoding this protein was cloned. Bioinformatics analysis of this protein indicated that it contains 448 amino acid residues, has a molecular weight of 48,794.16 Da and an isoelectric point of 6.04, and is a hydrophilic protein. In the secondary and tertiary structure of this protein, the proportion of α-helices and β-folds is similar, and the protein possesses a Peptidase_S8 conserved domain. Using BApNA as a substrate, it was found that the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF) can inhibit the W10 antifungal protein. PMSF concurrently reduced the inhibitory effects of the antifungal protein on Botrytis cinerea, showing that the W10 antifungal protein possesses serine protease activity. The W10 antifungal protein has good thermal stability. The study implies potential of this enzyme for biocontrol of fungal plant pathogens.