title: Mycobacterium tuberculosis mtrA merodiploid strains with point mutations in the signal-receiving domain of MtrA exhibit growth defects in nutrient broth.
abstract: The genetic and biochemical aspects of the essential Mycobacteriumtuberculosis 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 [Mg²+, Ca²+ or both] promote MtrB kinase autophosphorylation activity, but only Mg²+ 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 MtrA(D56E) and MtrA(D13A) proteins bound to the promoter of fbpB, the gene encoding antigen 85B protein, efficiently in the absence of phosphorylation, whereas MtrA(D56N) did not. We also show that M.tuberculosismtrA merodiploids overproducing MtrA(D13A), 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 MtrA(D13A) behaves like a constitutively active response regulator and that further characterization of mtrA merodiploid strains will provide valuable clues to the MtrAB system.
authors.affiliation: Biomedical Research, The University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
authors.forename: Maha
authors.initials: M
authors.lastname: Al Zayer
authors.forename: Dorota
authors.initials: D
authors.lastname: Stankowska
authors.forename: Renata
authors.initials: R
authors.lastname: Dziedzic
authors.forename: Krishna
authors.initials: K
authors.lastname: Sarva
authors.forename: Murty V
authors.initials: MV
authors.lastname: Madiraju
authors.forename: Malini
authors.initials: M
authors.lastname: Rajagopalan
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000217:Acyltransferases / Q000235:genetics; D000596:Amino Acids / Q000378:metabolism; D000942:Antigens, Bacterial / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D000596:Amino Acids; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C100938:MtrA protein, Bacteria; C079092:MtrB protein, Bacteria; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis