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Crystal structure of Salmonella typhimurium 2-methylcitrate synthase: Insights on domain movement and substrate specificity

Chittori, Sagar and Savithri, HS and Murthy, MRN (2011) Crystal structure of Salmonella typhimurium 2-methylcitrate synthase: Insights on domain movement and substrate specificity. In: Journal of Structural Biology, 174 (1). pp. 58-68.

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Official URL: http://dx.doi.org/10.1016/j.jsb.2010.10.008


2-Methylcitric acid (2-MCA) cycle is one of the well studied pathways for the utilization of propionate as a source of carbon and energy in bacteria such as Salmonella typhimurium and Escherichia coli. 2-Methylcitrate synthase (2-MCS) catalyzes the conversion of oxaloacetate and propionyl-CoA to 2-methylcitrate and CoA in the second step of 2-MCA cycle. Here, we report the X-ray crystal structure of S. typhimurium 2-MCS (StPrpC) at 2.4 A resolution and its functional characterization. StPrpC was found to utilize propionyl-CoA more efficiently than acetyl-CoA or butyryl-CoA. The polypeptide fold and the catalytic residues of StPrpC are conserved in citrate synthases (CSs) suggesting similarities in their functional mechanisms. In the triclinic P1 cell, StPrpC molecules were organized as decamers composed of five identical dimer units. In solution, StPrpC was in a dimeric form at low concentrations and was converted to larger oligomers at higher concentrations. CSs are usually dimeric proteins. In Gram-negative bacteria, a hexameric form, believed to be important for regulation of activity by NADH, is also observed. Structural comparisons with hexameric E. coil CS suggested that the key residues involved in NADH binding are not conserved in StPrpC. Structural comparison with the ligand free and bound states of CSs showed that StPrpC is in a nearly closed conformation despite the absence of bound ligands. It was found that the Tyr197 and Leu324 of StPrpC are structurally equivalent to the ligand binding residues His and Val, respectively, of CSs. These substitutions might determine the specificities for acyl-CoAs of these enzymes. (C) 2010 Elsevier Inc. All rights reserved.

Item Type: Journal Article
Publication: Journal of Structural Biology
Publisher: Elsevier Science
Additional Information: Copyright of this article belongs to Elsevier Science.
Keywords: Short chain fatty acids;Propionate metabolism;2-Methylcitric acid cycle;2-Methylcitrate synthase;Citrate synthase;X-ray crystallography
Department/Centre: Division of Biological Sciences > Biochemistry
Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 20 Apr 2011 05:38
Last Modified: 20 Apr 2011 05:38
URI: http://eprints.iisc.ac.in/id/eprint/36735

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