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J. Biol. Chem., Vol. 282, Issue 16, 11696-11704, April 20, 2007

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Structures of Activated Fructose-1,6-bisphosphatase from Escherichia coli

COORDINATE REGULATION OF BACTERIAL METABOLISM AND THE CONSERVATION OF THE R-STATE^*

From the Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011

The enteric bacterium Escherichia coli requires fructose-1,6-bisphosphatase (FBPase) for growth on gluconeogenic carbon sources. Constitutive expression of FBPase and fructose-6-phosphate-1-kinase coupled with the absence of futile cycling implies an undetermined mechanism of coordinate regulation involving both enzymes. Tricarboxylic acids and phosphorylated three-carbon carboxylic acids, all intermediates of glycolysis and the tricarboxylic acid cycle, are shown here to activate E. coli FBPase. The two most potent activators, phosphoenolpyruvate and citrate, bind to the sulfate anion site, revealed previously in the first crystal structure of the E. coli enzyme. Tetramers ligated with either phosphoenolpyruvate or citrate, in contrast to the sulfate-bound structure, are in the canonical R-state of porcine FBPase but nevertheless retain sterically blocked AMP pockets. At physiologically relevant concentrations, phosphoenolpyruvate and citrate stabilize an active tetramer over a less active enzyme form of mass comparable with that of a dimer. The above implies the conservation of the R-state through evolution. FBPases of heterotrophic organisms of distantly related phylogenetic groups retain residues of the allosteric activator site and in those instances where data are available exhibit activation by phosphoenolpyruvate. Findings here unify disparate observations regarding bacterial FBPases, implicating a mechanism of feed-forward activation in bacterial central metabolism.

Received for publication, December 4, 2006 , and in revised form, February 20, 2007.

^* This work was supported in part by National Institutes of Health Research Grant NS 10546 and by a graduate research fellowship award from the American Foundation for Aging Research. 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.

The atomic coordinates and structure factors (code 2OX3 and 2OWZ) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

¹ To whom correspondence should be addressed: Dept. of Biochemistry, Biophysics, and Molecular Biology, 4206 Molecular Biology Bldg., Iowa State University, Ames, IA 50011-3260. Tel.: 515-294-6116; Fax: 515-294-0453; E-mail: honzatko{at}iastate.edu.

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