Mechanistic features of Salmonella typhimurium propionate kinase (TdcD): Insights from kinetic and crystallographic studies

Chittori, Sagar and Simanshu, Dhirendra Kumar and Banerjee, Sanchari and Murthy, Ambika Mosale Venkatesh and Mathivanan, Subashini and Savithri, Handanahal Subbarao and Murthy, Mathur Ramabhadrashastry Narasimha (2013) Mechanistic features of Salmonella typhimurium propionate kinase (TdcD): Insights from kinetic and crystallographic studies. In: BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS, 1834 (10). pp. 2036-2044.

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Abstract

Short-chain fatty acids (SCFAs) play a major role in carbon cycle and can be utilized as a source of carbon and energy by bacteria. Salmonella typhimurium propionate kinase (StTdcD) catalyzes reversible transfer of the gamma-phosphate of ATP to propionate during L-threonine degradation to propionate. Kinetic analysis revealed that StTdcD possesses broad ligand specificity and could be activated by various SCFAs (propionate > acetate approximate to butyrate), nucleotides (ATP approximate to GTP > CTP approximate to TTP; dATP > dGTP > dCTP) and metal ions (Mg2+ approximate to Mn2+ > Co2+). Inhibition of StTdcD by tricarboxylic acid (TCA) cycle intermediates such as citrate, succinate, alpha-ketoglutarate and malate suggests that the enzyme could be under plausible feedback regulation. Crystal structures of StTdcD bound to PO4 (phosphate), AMP, ATP, Ap4 (adenosine tetraphosphate), GMP, GDP, GTP, CMP and CTP revealed that binding of nucleotide mainly involves hydrophobic interactions with the base moiety and could account for the broad biochemical specificity observed between the enzyme and nucleotides. Modeling and site-directed mutagenesis studies suggest Ala88 to be an important residue involved in determining the rate of catalysis with SCFA substrates. Molecular dynamics simulations on monomeric and dimeric forms of StTdcD revealed plausible open and closed states, and also suggested role for dimerization in stabilizing segment 235-290 involved in interfacial interactions and ligand binding. Observation of an ethylene glycol molecule bound sufficiently close to the gamma-phosphate in StTdcD complexes with triphosphate nucleotides supports direct in-line phosphoryl transfer. (C) 2013 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copyright for this article belongs to Elesvier
Keywords:	Salmonella typhimurium; Short-chain fatty acid metabolism; Enzyme assay; X-ray crystallography; Protein dynamics
Department/Centre:	Division of Biological Sciences > Biochemistry Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	30 Oct 2013 06:28
Last Modified:	30 Oct 2013 06:28
URI:	http://eprints.iisc.ac.in/id/eprint/47612

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