6onu
From Proteopedia
Complex structure of WhiB1 and region 4 of SigA in P21 space group.
Structural highlights
Function[WHIB1_MYCTU] Acts as a transcriptional repressor, inhibiting expression in vitro. Probably redox-responsive. The apo- but not holo-form binds to its own promoter as well as that of groEL2. Oxidized apo-form and nitrosylated holo-form also bind DNA. The apo-form has been shown to act as a protein disulfide reductase (PubMed:17157031) (PubMed:19016840), but also not to act as a protein disulfide reductase (PubMed:20929442).[1] [2] [3] [4] [SIGA_MYCTU] Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is the primary sigma factor during exponential growth (Probable).[5] [6] [7] Publication Abstract from PubMedWhiB1 is a monomeric iron-sulfur cluster-containing transcription factor in the WhiB-like family that is widely distributed in actinobacteria including the notoriously persistent pathogen Mycobacterium tuberculosis (M. tuberculosis). WhiB1 plays multiple roles in regulating cell growth and responding to nitric oxide stress in M. tuberculosis, but its underlying mechanism is unclear. Here we report a 1.85 A-resolution crystal structure of the [4Fe-4S] cluster-bound (holo-) WhiB1 in complex with the C-terminal domain of the sigma70-family primary sigma factor sigmaA of M. tuberculosis containing the conserved region 4 (sigmaA4). Region 4 of the sigma70-family primary sigma factors is commonly used by transcription factors for gene activation, and holo-WhiB1 has been proposed to activate gene expression via binding to sigmaA4. The complex structure, however, unexpectedly reveals that the interaction between WhiB1 and sigmaA4 is dominated by hydrophobic residues in the [4Fe-4S] cluster binding pocket, distinct from previously characterized canonical sigma704-bound transcription activators. Furthermore, we show that holo-WhiB1 represses transcription by interaction with sigmaA4in vitro and that WhiB1 must interact with sigmaA4 to perform its essential role in supporting cell growth in vivo. Together, these results demonstrate that holo-WhiB1 regulates gene expression by a non-canonical mechanism relative to well-characterized sigmaA4-dependent transcription activators. Structural basis of non-canonical transcriptional regulation by the sigmaA-bound iron-sulfur protein WhiB1 in M. tuberculosis.,Wan T, Li S, Beltran DG, Schacht A, Zhang L, Becker DF, Zhang L Nucleic Acids Res. 2019 Dec 6. pii: 5661089. doi: 10.1093/nar/gkz1133. PMID:31807774[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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