1vpe

From Proteopedia

Revision as of 15:05, 15 February 2008

CRYSTALLOGRAPHIC ANALYSIS OF PHOSPHOGLYCERATE KINASE FROM THE HYPERTHERMOPHILIC BACTERIUM THERMOTOGA MARITIMA

Overview

BACKGROUND: Phosphoglycerate kinase (PGK) is essential in most living, cells both for ATP generation in the glycolytic pathway of aerobes and for, fermentation in anaerobes. In addition, in many plants the enzyme is, involved in carbon fixation. Like other kinases, PGK folds into two, distinct domains, which undergo a large hinge-bending motion upon, catalysis. The monomeric 45 kDa enzyme catalyzes the transfer of the, C1-phosphoryl group from 1, 3-bisphosphoglycerate to ADP to form, 1,3-bisphosphoglycerate to ADP to form 3-phosphoglycerate and ATP. For, decades, the conformation of the enzyme during catalysis has been, enigmatic. The crystal structure of PGK from the hyperthermophilic, organism Thermotoga maritima (TmPGK) represents the first structure of an, extremely thermostable PGK. It adds to a series of four known crystal, structures of PGKs from mesophilic via moderately thermophilic to a, hyperthermophilic organism, allowing a detailed analysis of possible, structural determinants of thermostability. RESULTS: The crystal structure, of TmPGK was determined to 2.0 A resolution, as a ternary complex with the, product 3-phosphoglycerate and the product analogue AMP-PNP, (adenylyl-imido diphosphate). The complex crystallizes in a closed, conformation with a drastically reduced inter-domain angle and a distance, between the two bound ligands of 4.4 A, presumably representing the active, conformation of the enzyme. The structure provides new details of the, catalytic mechanism. An inter-domain salt bridge between residues Arg62, and Asp200 forms a strap to hold the two domains in the closed state. We, identify Lys197 as a residue involved in stabilization of the transition, state phosphoryl group, and so term it the 'phosphoryl gripper'., CONCLUSIONS: The hinge-bending motion of the two domains upon closure of, the structure, as seen in the Trypanosoma PGK structure, is confirmed., This closed conformation obviously occurs after binding of both substrates, and is locked by the Arg62-Asp200 salt bridge. Re-orientations in the, conserved active-site loop region around Thr374 also bring both domains, into direct contact in the core region of the former inter-domain cleft, to form the complete catalytic site. Comparison of extremely thermostable, TmPGK with less thermostable homologues reveals that its increased, rigidity is achieved by a raised number of intramolecular interactions, such as an increased number of ion pairs and additional stabilization of, alpha helix and loop regions. The covalent fusion with triosephosphate, isomerase might represent an additional stabilization strategy.

About this Structure

1VPE is a Single protein structure of sequence from Thermotoga maritima with , and as ligands. The following page contains interesting information on the relation of 1VPE with [The Glycolytic Enzymes]. Active as Phosphoglycerate kinase, with EC number 2.7.2.3 Full crystallographic information is available from OCA.

Reference

Closed structure of phosphoglycerate kinase from Thermotoga maritima reveals the catalytic mechanism and determinants of thermal stability., Auerbach G, Huber R, Grattinger M, Zaiss K, Schurig H, Jaenicke R, Jacob U, Structure. 1997 Nov 15;5(11):1475-83. PMID:9384563

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