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Publication Abstract from PubMed

Cholesterol can be a major carbon source for Mycobacterium tuberculosis during infection, both at an early stage in the macrophage phagosome and later within the necrotic granuloma. KstR is a highly conserved TetR-family transcriptional repressor (TFR) that regulates a large set of genes responsible for cholesterol catabolism. Many genes in this regulon, including kstR, are either induced during infection or are essential for survival of Mtb in vivo. In this study we identified two ligands for KstR, both of which are CoA thioester cholesterol metabolites with four intact steroid rings. A metabolite in which one of the rings was cleaved was not a ligand. We confirmed the ligand-protein interactions using instrinsic tryptophan fluorescence, and showed that ligand binding strongly inhibited KstR-DNA binding using surface plasmon resonance (IC50 for ligand = 25 nM). Crystal structures of the ligand-free form of KstR show variability in the position of the DNA-binding domain (DBD). In contrast, structures of KstR-ligand complexes are highly similar to each other and demonstrate a position of the DBD that is unfavourable for DNA binding. Comparison of ligand-bound and ligand-free structures identifies residues involved in ligand specificity and reveals a distinctive mechanism by which the ligand-induced conformational change mediates DNA release.

The structure of the transcriptional repressor Kstr in complex with CoA thioester cholesterol metabolites sheds light on the regulation of cholesterol catabolism in Mycobacterium tuberculosis.,Ho NA, Dawes SS, Crowe AM, Casabon IE, Gao C, Kendall SL, Baker EN, Eltis LD, Lott JS J Biol Chem. 2016 Feb 8. pii: jbc.M115.707760. PMID:26858250^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.