Journal of Biological Chemistry
Volume 283, Issue 31, 1 August 2008, Pages 21693-21702
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Enzyme Catalysis and Regulation
Trapping of the Thioacylglyceraldehyde-3-phosphate Dehydrogenase Intermediate from Bacillus stearothermophilus: DIRECT EVIDENCE FOR A FLIP-FLOP MECHANISM*

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The crystal structure of the thioacylenzyme intermediate of the phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Bacillus stearothermophilus has been solved at 1.8Å resolution. Formation of the intermediate was obtained by diffusion of the natural substrate within the crystal of the holoenzyme in the absence of inorganic phosphate. To define the soaking conditions suitable for the isolation and accumulation of the intermediate, a microspectrophotometric characterization of the reaction of GAPDH in single crystals was carried out, following NADH formation at 340 nm. When compared with the structure of the Michaelis complex ( Didierjean, C., Corbier, C., Fatih, M., Favier, F., Boschi-Muller, S., Branlant, G., and Aubry, A. (2003) J. Biol. Chem. 278, 12968-12976) the 206-210 loop is shifted and now forms part of the so-called “new Pi” site. The locations of both the O1 atom and the C3-phosphate group of the substrate are also changed. Altogether, the results provide evidence for the flipping of the C3-phosphate group occurring concomitantly or after the redox step.

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The atomic coordinates and structure factors (code 3cmc) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

*

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1

Fellow of the French Ministère de la Recherche et des Nouvelles Technologies.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1.