Prokaryotic Expression, Identification and Bioinformatics Analysis of the Mycobacterium tuberculosis Rv3807c Gene Encoding the Putative Enzyme Committed to Decaprenylphosphoryl-d-arabinose Synthesis.

Decaprenylphosphoryl-d-arabinofuranosyl (DPA), the immediate donor for the polymerized d-Araf residues of mycobacterial arabinan, is synthesized from 5-phosphoribose-1-diphosphate (PRPP) in three-step reactions. (i) PRPP is transferred to decaprenyl-phosphate (DP) to form decaprenylphosphoryl-d-5-phosphoribose (DPPR). (ii) DPPR is dephosphorylated to form decaprenylphosphoryl-d-ribose (DPR). (iii) DPR is formed to DPA by the epimerase. Mycobacterium tuberculosis Rv3806c and heteromeric Rv3790/Rv3791 have been identified as the PRPP: decaprenyl-phosphate 5-phosphoribosyltransferase and the epimerase respectively. Rv3807c, however, as the candidate of phospholipid phosphatase, catalyzing the biosynthesis of decapreny-l-phosphoryl-ribose (DPR) from decaprenylphosphoryl-β-d-5-phosphoribose by dephosphorylating, has no direct experimental evidence of its essentiality in any species of mycobacterium. In this study, Rv3807c gene was amplified from the genome of M. tuberculosis H37Rv by PCR, and was successfully expressed in Escherichia coli BL21 (DE3) via the recombinant plasmid pColdII-Rv3807c. The resulting protein with the 6× His-tag was identified by SDS-PAGE and Western blotting. The protein was predicted through bioinformatics to contain three transmembrane domains, the N-terminal peptide, and a core structure with phosphatidic acid phosphatase type2/haloperoxidase. This study provides biochemical and bioinformatics evidence for the importance of Rv3807c in mycobacteria, and further functional studies will be conducted for validating Rv3807c as a promising phospholipid phosphatase in the synthetic pathway of DPA.