Mass spectrometry identification of secreted proteins from Bacillus firmus and analysis of its secretive sequences

Abstract:

Abstract:［Objective］Bacillus firmus was a common probiotics bacteria in nature and widely used in the shrimp aquaculture．In order to construct expression vectors for secretive proteins，we identified several major secretive proteins of Bacillus firmus by mass spectrometry and analyzed their gene sequences to find signal peptide sequences．［Methods］The secreted proteins of Bacillus firmus were extracted and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)．The 3 highly expressed protein bands in the SDS-PAGE were identified by mass spectrometry Matrix Assisted Laser Desorption Ionization (MALDI)-Time of Flight (TOF)/Time of Flight (TOF) and the sequences were downloaded from National Center for Biotechnology Information (NCBI) database．Then Polymerase Chain Reaction (PCR) primers were designed according to the downloaded sequences and specific DNA bands were amplified sequenced and bioinformatics analyzed．［Results］The proteins were identified as the putative chitinase，enterotoxin A and protein BCG9842 of Bacillus firmus．Three signal peptides were conformed by using the online software SignaIP 3. 0，namely bf-43，bf-37 and bf-16. The cellular localization of the secreted sequences were analyzed by PSORT． And we found that bf-43 located in the outer membrane of cells，bf-37 and bf-16 located in the extracellular cell．［Conclusion］3 major secreted proteins of Bacillus firmus have been identified．3 possible signal peptides were obtained and will be useful for the construction of expression vectors for secretive proteins．