title: Mycobacterium tuberculosis response regulators, DevR and NarL, interact in vivo and co-regulate gene expression during aerobic nitrate metabolism.
abstract: 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 His(241) and Asp(61) 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 with or without 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 augmented by NarL. Specifically, NarL itself was unable to bind to the narK2, acg, and 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 a heterodimer, as a novel mechanism for co-regulation of gene expression by the DevRS/DosT and NarL/NarS regulatory systems.
authors: From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and vmal71@gmail.com.
authors: Vandana
authors: V
authors: Malhotra
authors: the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India.
authors: Ruchi
authors: R
authors: Agrawal
authors: From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and.
authors: Tammi R
authors: TR
authors: Duncan
authors: the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India deepak@mrdg.iisc.ernet.in.
authors: Deepak K
authors: DK
authors: Saini
authors: From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and.
authors: Josephine E
authors: JE
authors: Clark-Curtiss
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007700:Kinetics; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D009566:Nitrates; D009573:Nitrites; D014157:Transcription Factors
keywords: Bacterial Signal Transduction; Coregulation; DevR; Gene Expression; Mycobacterium tuberculosis; NarL; Nitrogen Metabolism; Protein-Protein Interaction; Response Regulators; Two-component System