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Antitoxin autoregulation of M. tuberculosis toxin-antitoxin expression through negative cooperativity arising from multiple inverted repeat sequences

DOI: 10.1042/BCJ20200368 DOI Help

Authors: Izaak Beck (Durham University) , Ben Usher (Durham University) , Hannah G Hampton (University of Otago) , Peter C. Fineran (University of Otago) , Tim R. Blower (Durham University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: June 2020
Diamond Proposal Number(s): 18598

Open Access Open Access

Abstract: Toxin-antitoxin systems play key roles in bacterial adaptation, including protection from antibiotic assault and infection by bacteriophages. The type IV toxin-antitoxin system AbiE encodes a DUF1814 nucleotidyltransferase-like toxin, and a two-domain antitoxin. In Streptococcus agalactiae, the antitoxin AbiEi negatively autoregulates abiE expression through positively co-operative binding to inverted repeats within the promoter. The human pathogen Mycobacterium tuberculosis encodes four DUF1814 putative toxins, two of which have antitoxins homologous to AbiEi. One such M.tuberculosis antitoxin, named Rv2827c, is required for growth and whilst the structure has previously been solved, the mode of regulation is unknown. To complete the gaps in our understanding, we first solved the structure of S. agalactiae AbiEi to 1.83 Å resolution for comparison with M.tuberculosis Rv2827c. AbiEi contains an N-terminal DNA binding domain and C-terminal antitoxicity domain, with bilateral faces of opposing charge. The overall AbiEi fold is similar to Rv2827c, though smaller, and with a 65º difference in C-terminal domain orientation. We further demonstrate that, like AbiEi, Rv2827c can autoregulate toxin-antitoxin operon expression. In contrast to AbiEi, the Prv2827c promoter contains two sets of inverted repeats, which bind Rv2827c with differing affinities depending on the sequence consensus. Surprisingly, Rv2827c bound with negative co-operativity to the full Prv2827c promoter, demonstrating an unexpectedly complex form of transcriptional regulation.

Journal Keywords: Toxin-antitoxin system; Co-operativity; Mycobacterium tuberculosis; Transcription; Regulation; Structural biology

Diamond Keywords: Tuberculosis (TB); Bacteria

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography

Added On: 24/06/2020 14:03


Discipline Tags:

Pathogens Infectious Diseases Health & Wellbeing Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)