Mycobacterium tuberculosis (MTB) synchronizes a number of processes and controls a series of events to subvert host defense mechanisms for the sake of residing inside macrophages. Besides these, MTB also possesses a wide range of signal enzyme systems, including eleven serine threonine protein kinases (STPKs). The present study describes STPK modulated modification in one of the hypothetical proteins of the RD1 region; EspJ (ESX-1 secretion associated protein), which is predicted to be involved in virulence of MTB. We have employed knock-out MTB, and M. bovis BCG as a surrogate strain to elaborate the consequence of the phosphorylation of EspJ. The molecular and mass spectrometric analyses in this study, confirmed EspJ as one of the substrates of STPKs. The ectopic expression of phosphoablative mutants of espJ in M. bovis BCG also articulated the effect of phosphorylation on the growth and in survival of mycobacteria. Importantly, the level of phosphorylation of EspJ also differed between pathogenic H37 Rv (Rv) and non pathogenic H37 Ra (Ra) strains of MTB. This further suggested that to a certain extent, the STPKs mediated phosphorylation may be accountable, in determining the growth and in intra-cellular survival of mycobacteria.
