Cloning, expression, purification and bioinformatic analysis of 2-methylcitrate synthase from Mycobacterium tuberculosis.

Objective: To clone, express and purify 2-methylcitrate synthase (Rv1131) gene of Mycobacterium tuberculosis (M. tuberculosis) and to study its structural characteristics using various bioinformatics tools.

Methods: Rv1131 gene was amplified by polymerase chain reaction using M. tuberculosis H37Rv genomic DNA and cloned into pGEM-T easy vector and sequenced. The gene was sub-cloned in pET28c vector, expressed in Escherichia coli BL21 (E. coli BL21) (DE3) cells and the recombinant protein was identified by Western blotting. The protein was purified using Nickel affinity chromatography and the structural characteristics like sub-cellular localization, presence of transmembrane helices and secondary structure of the protein were predicted by bioinformatics tools. Tertiary structure of the protein and phylogenetic analysis was also established by in silico analysis.

Results: The expression of the recombinant protein (Rv1131) was confirmed by western blotting using anti-HIS antibodies and the protein was purified from the soluble fraction. In silico analysis showed that the protein contains no signal peptide and transmembrane helices. Active site prediction showed that the protein has histidine and aspartic acid residues at 242, 281 & 332 positions respectively. Phylogenetic analysis showed 100% homology with major mycobacterial species. Secondary structure predicts 2-methylcitrate synthase contain 51.9% alpha-helix, 8.7% extended strand and 39.4% random coils. Tertiary structure of the protein was also established.

Conclusions: The enzyme 2-methylcitrate synthase from M. tuberculosis H37Rv has been successfully expressed and purified. The purified protein will further be utilized to develop assay methods for screening new inhibitors.