Abstract
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.
Highlights
Serine Threonine Serine Threonine Serine Threonine Serine Threonine strains which might be regulated by PhoP8
An added criterion for the elaborative study of this protein has been the presence of Rxx(S/T) motif, which exists in most of the substrates for STPK, including FtsZ protein, which regulates cell division in mycobacteria[14]
With the advent of STPKs in mycobacteria it has been well documented that phosphorylation of proteins involved in determining the virulence, effects growth and later the pathogenicity of mycobacteria[15,16]
Summary
Serine Threonine Serine Threonine Serine Threonine Serine Threonine strains which might be regulated by PhoP8. EspJ, so far known as a hypothetical protein, has been putatively categorized as a regulatory protein[12] and annotated under functional category “cell wall and cell process” in Tuberculist database This protein is present both in Ra and in Rv strains of mycobacteria but is absent in M. bovis BCG. Generation of phosphoablative mutants by site directed mutagenesis, followed by the transfer of these phosphoablative alleles in M. bovis BCG; we have deciphered its role in the growth and in persistence of mycobacteria. This phenotype was confirmed by knocking-out the gene from MTB and complementing with wild type and phosphoablative genes
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