Mycobacterium tuberculosis mtrA merodiploid strains with point mutations in the signal-receiving domain of MtrA exhibit growth defects in nutrient broth

Maha Al Zayer, Dorota Stankowska, Renata Dziedzic, Krishna Sarva, Murty V. Madiraju, Malini Rajagopalan

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The genetic and biochemical aspects of the essential Mycobacterium tuberculosis MtrAB two-component regulatory signal transduction (2CRS) system have not been extensively investigated. We show by bacterial two-hybrid assay that the response regulator (RR) MtrA and the sensor kinase MtrB interact. We further demonstrate that divalent metal ions [Mg(2+), Ca(2+) or both] promote MtrB kinase autophosphorylation activity, but only Mg(2+) promotes phosphotransfer to MtrA. Replacement of the conserved aspartic acid residues at positions 13 and 56 with alanine (D13A), glutamine (D56E) or asparagine (D56N) prevented MtrA phosphorylation, indicating that these residues are important for phosphorylation. The MtrAD56E and MtrAD13A proteins bound to the promoter of fbpB, the gene encoding antigen 85B protein, efficiently in the absence of phosphorylation, whereas MtrAD56N did not. We also show that M. tuberculosis mtrA merodiploids overproducing MtrAD13A, unlike cells overproducing wild-type MtrA, grow poorly in nutrient broth and show reduced expression of fbpB. These latter findings are reminiscent of a phenotype associated with MtrA overproduction during intramacrophage growth. Our results suggest that MtrAD13A behaves like a constitutively active response regulator and that further characterization of mtrA merodiploid strains will provide valuable clues to the MtrAB system.

Original languageEnglish
Pages (from-to)210-218
Number of pages9
JournalPlasmid
Volume65
Issue number3
DOIs
StatePublished - May 2011

Keywords

  • Merodiploids
  • Mutants
  • Mycobacterium tuberculosis
  • Real-time PCR
  • Response regulator
  • Signal transduction

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