Browsing by Author "Crack, Jason C."

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    Cmr is a redox-responsive regulator of DosR that contributes to M. tuberculosis virulence.
    (Oxford University Press, 2017-05-08) Smith, Laura J.; Bochkareva, Aleksandra; Rolfe, Matthew D.; Hunt, Debbie M.; Kahramanoglou, Christina; Braun, Yvonne; Rodgers, Angela; Blockley, Alix; Coade, Stephen; Lougheed, Kathryn E. A.; Hafneh, Nor Azian; Glenn, Sarah M.; Crack, Jason C.; Le Brun, Nick E.; Saldanha, José W.; Makarov, Vadim; Nobeli, Irene; Arnvig, Kristine; Mukamolova, Galina V.; Buxton, Roger S.; Green, Jeffrey
    Mycobacterium tuberculosis (MTb) is the causative agent of pulmonary tuberculosis (TB). MTb colonizes the human lung, often entering a non-replicating state before progressing to life-threatening active infections. Transcriptional reprogramming is essential for TB pathogenesis. In vitro, Cmr (a member of the CRP/FNR super-family of transcription regulators) bound at a single DNA site to act as a dual regulator of cmr transcription and an activator of the divergent rv1676 gene. Transcriptional profiling and DNA-binding assays suggested that Cmr directly represses dosR expression. The DosR regulon is thought to be involved in establishing latent tuberculosis infections in response to hypoxia and nitric oxide. Accordingly, DNA-binding by Cmr was severely impaired by nitrosation. A cmr mutant was better able to survive a nitrosative stress challenge but was attenuated in a mouse aerosol infection model. The complemented mutant exhibited a ∼2-fold increase in cmr expression, which led to increased sensitivity to nitrosative stress. This, and the inability to restore wild-type behaviour in the infection model, suggests that precise regulation of the cmr locus, which is associated with Region of Difference 150 in hypervirulent Beijing strains of Mtb, is important for TB pathogenesis.
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    Structure of a Wbl protein and implications for NO sensing by M. tuberculosis
    (Nature Publishing Group, 2017-12-22) Kudhair, B.K.; Hounslow, A.M.; Rolfe, Matthew D.; Crack, Jason C.; Hunt, Debbie M.; Buxton, Roger S.; Smith, Laura J.; Le Brun, Nick E.; Williamson, M.P.; Green , J.
    Mycobacterium tuberculosis causes pulmonary tuberculosis (TB) and claims ~1.8 million human lives per annum. Host nitric oxide (NO) is important in controlling TB infection. M. tuberculosis WhiB1 is a NO-responsive Wbl protein (actinobacterial iron–sulfur proteins first identified in the 1970s). Until now, the structure of a Wbl protein has not been available. Here a NMR structural model of WhiB1 reveals that Wbl proteins are four-helix bundles with a core of three α-helices held together by a [4Fe-4S] cluster. The iron–sulfur cluster is required for formation of a complex with the major sigma factor (σA) and reaction with NO disassembles this complex. The WhiB1 structure suggests that loss of the iron–sulfur cluster (by nitrosylation) permits positively charged residues in the C-terminal helix to engage in DNA binding, triggering a major reprogramming of gene expression that includes components of the virulence-critical ESX-1 secretion system.