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Publication Abstract from PubMed

Mycobacterium tuberculosis (Mtb) is the leading cause of death due to a bacterial infection. The success of the Mtb pathogen has largely been attributed to the nonreplicating, persistence phase of the life cycle, for which the glyoxylate shunt is required. In Escherichia coli flux through the shunt is controlled by regulation of isocitrate dehydrogenase (ICDH). In Mtb, the mechanism of regulation is unknown, and currently there is no mechanistic or structural information on ICDH. We optimized expression and purification to a yield high enough to perform the first detailed kinetic and structural studies for Mtb ICDH-1. A large solvent kinetic isotope effect (D2OV = 3.0 +/- 0.2, D2O[V/Kisocitrate] = 1.5 +/- 0.3) and a smaller primary kinetic isotope effect (DV = 1.3 +/- 0.1, D[V/K[2R-2H]isocitrate] = 1.5 +/- 0.2) allowed us to perform the first multiple kinetic isotope effect studies on any ICDH and suggest a chemical mechanism. In this mechanism, protonation of the enolate to form product alpha-ketoglutarate is the rate-limiting step. We report the first structure of Mtb ICDH-1 to 2.18 A by X-ray crystallography with NADPH and Mn2+ bound. It is a homodimer in which each subunit has a Rossmann fold, and a common top domain of interlocking beta sheets. Mtb ICDH-1 is most structurally similar to the R132H mutant human ICDH found in glioblastomas. Similar to human R132H ICDH, Mtb ICDH-1 also catalyses the formation of alpha-hydroxyglutarate. Our data suggest that regulation of Mtb ICDH-1 is novel.

Structure, Kinetic, and Chemical Mechanism of Isocitrate Dehydrogenase-1 from Mycobacterium tuberculosis.,Quartararo CE, Hazra S, Hadi T, Blanchard JS Biochemistry. 2013 Feb 14. PMID:23409873^[1]

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