Mycobacterium tuberculosis Response Regulators, DevR and NarL Interact In Vivo and Co-Regulate Gene Expression during Aerobic Nitrate Metabolism [Signal Transduction]

February 6th, 2015 by Malhotra, V., Agrawal, R., Duncan, T. R., Saini, D. K., Clark-Curtiss, J. E.

Mycobacterium tuberculosis genes Rv0844c/Rv0845 encoding the NarL response regulator and NarS histidine kinase are hypothesized to constitute a two-component system involved in the regulation of nitrate metabolism. However, there is no experimental evidence to support this. In this study, we established M. tuberculosis NarL/NarS as a functional two-component system and identified His241 and Asp61 as conserved phosphorylation sites in NarS and NarL, respectively. Transcriptional profiling between M. tuberculosis H37Rv and a ΔnarL mutant strain during exponential growth in broth cultures ± nitrate defined an ≈30 gene NarL regulon that exhibited significant overlap with DevR-regulated genes, thereby implicating a role for the DevR response regulator in the regulation of nitrate metabolism. Notably, expression analysis of a subset of genes common to NarL and DevR-regulons in M. tuberculosis ΔdevR, ΔdevSΔdosT and ΔnarL mutant strains, revealed that in response to nitrite produced during aerobic nitrate metabolism, the DevRS/DosT regulatory system plays a primary role that is augumented by NarL. Specifically, NarL itself was unable to bind to the narK2, acg, Rv3130c promoters in phosphorylated or unphosphorylated form; however, its interaction with DevR~P resulted in cooperative binding, thereby enabling co-regulation of these genes. These findings support the role of physiologically-derived nitrite as a metabolic signal in mycobacteria. We propose NarL-DevR binding possibly as heterodimer, as a novel mechanism for co-regulation of gene expression by the DevRS/DosT and NarL/NarS regulatory systems.
  • Posted in Journal of Biological Chemistry, Publications
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