Abstract:
PknJ (Rv2088) is a serine / threonine protein kinase of mycobacteria which is present in Mycobacterium tuberculosis (MTB) but its gene is absent in Mycobacterium smegmatis (MS), a fast grower and non-pathogenic species of mycobacteria. The heterologous expression of MTB specific PknJ in MS altered the growth of recombinant mycobacteria highlighting one of the characteristics of this protein. This nature of the protein was further confirmed when M. bovis BCG (BCG) containing anti-sense copy of pknJ resulted in the increased growth of BCG. The real time RNA quantification analyses pointed out towards increased expression of this protein during infection of THP-1 macrophage cells which further emphasized that the protein is essential for the intracellular survival of mycobacteria. The differential in gel electrophoresis (DIGE) data followed by mass spectroscopy suggested that PknJ is involved in regulation of Pyruvate Kinase A (Rv1617). Since Pyruvate Kinase A (PK) is one of the key enzymes which controls glycolytic cycle in mycobacteria, we looked for its interaction with PknJ during extracellular and intracellular growth of mycobacteria. In order to identify the specific residue(s) involved in post-translational modification, the phospho-null mutants of PK were generated and their substrate specificities in response to PknJ were assessed through kinase assay. The findings thus underlined that the PK activity is predominantly dependent on the threonine residue at the 94th position and further suggested that this site may be plausible in intracellular survival of mycobacteria upon phosphorylation with PknJ
