Expression,Purification and Analysis of the Biological Characteristics of Klebsiella pneumoniae CRP Protein

Objective:This study aimed to prokaryotically express and purify the protein encoded by KP1_RS23625 gene(crp)of Klebsiella pneumoniae in vitro,and analyze the biological function of CRP protein by means of biological information. Methods:CRP gene was amplified and cloned,and then subcloned into pET-28a(+)plasmid to construct a recombinant expression vector. In vitro induced expression,purification of the target protein were done,and analyzed by SDS-PAGE electrophoresis. Furthermore,the biological function of CRP protein was analyzed using several biological information softwares:The general biological characteristics of the target protein including physicochemical properties,hydrophobicity,signal peptide,transmembrane region,secondary and tertiary structure were analyzed via ProtParam,Protscale,SignalP4.1 Service,TMHMM Server v.2.0,SOPMA and SWISS-MODEL softwares respectively,the functional characteristics of domain and phosphorylation site were predicted by the CDD database and online Net Phos 3.1 Sever software,respectively,and protein crosslink interaction was performed through ATRING 11.0 interactive database. Results:The recombinant target protein expression vector pET-28a-crp was successfully constructed,and the CRP target protein was obtained by prokaryotic induction expression and nickel column affinity absorption method,and the electrophoresis results showed that the CRP protein is a water-soluble protein,and the molecular weight of the recombinant protein including the tag protein(4 kDa)was about 27 kDa. Bioinformatics analysis showed that CRP protein had a size of 23.65 kDa,which was a hydrophilic protein and consistent with electrophoresis results,and had no transmembrane domain,no signal peptide. The secondary structure was mainly composed of α-helix and irregular coils,of which α-helix accounts for more than 40% and the structure was loose. The tertiary structure model was successfully constructed. The analysis of CRP protein domain indicated that it contained one functional domain,belonging to the PRK11753 super family,the modification site and annotation analysis showed that the target protein contains 20 phosphorylation sites,which could interact with multiple proteins. Conclusion:In this study,Klebsiella pneumoniae CRP protein with a higher purity was successfully obtained by genetic engineering methods and the biological characteristics were revealed,which could provide basic support for the clinical treatment of K. pneumoniae infection.