Redox- and pH-responsive transcriptional regulator WhiB3

UniProtKB accession:  P9WF41

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UniProtKB description:  A redox-sensitive transcriptional regulator. Maintains intracellular redox homeostasis by regulating catabolic metabolism and polyketide biosynthesis (PubMed:17609386, PubMed:19680450). Regulates expression of the redox buffer ergothioneine (ERG) in a carbon-source-dependent manner; loss of ERG or mycothiol (MSH, the other major redox buffer in this bacteria) leads to respiratory alterations and bioenergetic deficiencies that negatively impact virulence (PubMed:26774486). In response to low external pH (like that found in host macrophage phagosomes) alters endogenous gene expression leading to acid resistance; MSH and WhiB3 are probably part of a regulatory circuit that mediates gene expression upon acid stress (PubMed:26637353). Regulates pathogenic lipid synthesis, coordinating proprionate flux (and other host-derived fatty acid oxidation intermediates) into methyl-branched fatty acids (polyacyltrehalose, phthiocerol dimycocerosates, sulfolipids) and the storage lipid triacylglycerol, functioning as reductive sink (PubMed:19680450). During intracellular growth M.tuberculosis uses host fatty acids as an energy source, generating large quantities of proprionate and NADH/NADPH, which are toxic and highly reducing respectively. WhiB3 is thought to help dissipate proprionate and NADH/NADPH by switching to the in vivo carbon source and via lipid anabolism (PubMed:19680450). Responds to NO and O(2) (PubMed:17609386). Regulates expression of genes encoding modular polyketide synthases such as pks2, pks3 and fbpA (PubMed:19680450). The oxidized apo-form of WhiB3 binds DNA (with 2 intramolecular disulfide bonds); holo-WhiB3 (with the 4Fe-4S cluster) binds DNA considerably less well (PubMed:19680450). Discriminates poorly between specific and non-specific DNA-binding. Plays a role in virulence and nutritional stress (PubMed:11880648, PubMed:17609386, PubMed:26637353). In its apo-form can act as a protein disulfide reductase (PubMed:18550384).