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J. Bacteriol., 06 1996, 3314-3321, Vol 178, No. 11
LE Via, R Curcic, MH Mudd, S Dhandayuthapani, RJ Ulmer and V Deretic
A putative two-component system, mtrA-mtrB, was isolated from M.
tuberculosis H37Rv by using phoB from Pseudomonas aeruginosa as a
hybridization probe. The predicted gene product of mtrA displayed high
similarity with typical response regulators, including AfsQ1, PhoB, PhoP,
and OmpR. The predicted gene product of mtrB displayed similarities with
the histidine protein kinases AfsQ2, PhoR, and EnvZ and other members of
this class of proteins. Expression analysis in the T7 system showed that
mtrA encoded a polypeptide with an apparent molecular mass of 30 kDa. MtrA
was overproduced, purified, and demonstrated to participate in typical
phosphotransfer reactions using a heterologous histidine protein kinase,
CheA, as a phosphoryl group donor. Mycobacterium bovis BCG, harboring an
mtrA-gfp (green fluorescent protein cDNA) transcriptional fusion, was used
to monitor mtrA expression in infected J774 monolayers. Flow cytometric and
fluorescence microscopic analyses indicated that the mtrA promoter was
activated upon entry and incubation in J774 macrophages. In contrast, the
hsp60-gfp fusion displayed no change in expression under the growth
conditions tested. These results suggest a potential role for mtrA in
adaptation of the M. tuberculosis complex organisms to environmental
changes which may include intracellular conditions.
Copyright © 1996, American Society for Microbiology
Elements of signal transduction in Mycobacterium tuberculosis: in vitro phosphorylation and in vivo expression of the response regulator MtrA
Department of Microbiology, University of Texas Health Science Center at San Antonio 78284-7758, USA.
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