title: Mycobacterium tuberculosis Rv1474c is a TetR-like transcriptional repressor that regulates aconitase, an essential enzyme and RNA-binding protein, in an iron-responsive manner.
abstract: Mycobacterium tuberculosis (M.tb), tuberculosis (TB) causing bacteria, employs several mechanisms to maintain iron homeostasis which is critical for its survival and pathogenesis. M.tb aconitase (Acn), a [4Fe-4S] cluster-containing essential protein, apart from participating in energy cycle, also binds to predicted iron-responsive RNA elements. In this study, we identified Rv1474c as a regulator of its operonic partner acn and carried out its biochemical and functional characterization. The binding motif for Rv1474c in the upstream region of acn (Rv1475c)-Rv1474c operon was verified by gel-shift assays. Reporter assays in E. coli followed by over-expression studies in mycobacteria, using both wild type and a DNA-binding defective mutant, demonstrated Rv1474c as a Tet-R like repressor of acn. Rv1474c, besides binding tetracycline, could also bind iron which negatively influenced its DNA binding activity. Further, a consistent decrease in the relative transcript levels of acn when M.tb was grown in iron-deficient conditions as compared to either normal or other stress conditions, indicated regulation of acn by Rv1474c in an iron-responsive manner in vivo. The absence of homologs in the human host and its association with indispensable iron homeostasis makes Rv1474c an attractive target for designing novel anti-mycobacterials.
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana, India.
authors.forename: Kannan
authors.initials: K
authors.lastname: Balakrishnan
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana, India.
authors.forename: Krishnaveni
authors.initials: K
authors.lastname: Mohareer
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana, India. Electronic address: sbsl@uohyd.ac.in.
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Banerjee
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D007501:Iron / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013752:Tetracycline / Q000378:metabolism / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012097:Repressor Proteins; D007501:Iron; D000154:Aconitate Hydratase; D013752:Tetracycline
keywords: Iron homeostasis; Iron-responsive-proteins; M.tb aconitase; TetR; Transcription factors