title: Regulation of the KstR2 regulon of Mycobacterium tuberculosis by a cholesterol catabolite.
abstract: Cholesterol catabolism is widespread in actinobacteria and is critical for Mycobacterium tuberculosis (Mtb) virulence. Catabolism of steroid nucleus rings C and D is poorly understood: it is initiated by the CoA thioesterification of 3aα-H-4α(3'-propanoate)-7aβ-methylhexahydro-1,5-indanedione (HIP) by FadD3, whose gene is part of the KstR2 regulon. In Mtb, genes of this regulon were upregulated up to 30- and 22-fold during growth on cholesterol and HIP, respectively, versus another minimal medium. In contrast, genes involved in degrading the cholesterol side-chain and nucleus rings A and B were only upregulated during growth on cholesterol. Similar results were obtained in Rhodococcus jostii RHA1. Moreover, the regulon was not upregulated in a ΔfadD3 mutant unable to produce HIP-CoA. In electrophoretic mobility shift assays, HIP-CoA relieved the binding of KstR2(Mtb) to each of three KstR2 boxes: CoASH, HIP and a related CoA thioester did not. Inspection of the structure of KstR2(RHA1) revealed no obvious HIP-CoA binding pocket. The results establish that Mtb can catabolize the entire cholesterol molecule and that HIP-CoA is an effector of KstR2. They further indicate that KstR2 specifically represses the expression of the HIP degradation genes in actinobacteria, which encode a lower pathway involved in the catabolism of multiple steroids.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Israël
authors.initials: I
authors.lastname: Casabon
authors.forename: Song-Hua
authors.initials: SH
authors.lastname: Zhu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Otani
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: William W
authors.initials: WW
authors.lastname: Mohn
authors.forename: Lindsay D
authors.initials: LD
authors.lastname: Eltis
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011485:Protein Binding; D018085:Regulon; D012097:Repressor Proteins / Q000378:metabolism*; D012240:Rhodococcus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D012097:Repressor Proteins; D002784:Cholesterol