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J. Biol. Chem., Vol. 282, Issue 27, 19948-19957, July 6, 2007
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1
2
From the
Macromolecular Crystallography Group, European Synchrotron Radiation Facility, 38043 Grenoble, France and
Division of Biological Chemistry and Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
High resolution structures of Staphylococcus aureus D-tagatose-6-phosphate kinase (LacC) in two crystal forms are herein reported. The structures define LacC in apoform, in binary complexes with ADP or the co-factor analogue AMP-PNP, and in a ternary complex with AMP-PNP and D-tagatose-6-phosphate. The tertiary structure of the LacC monomer, which is closely related to other members of the pfkB subfamily of carbohydrate kinases, is composed of a large
/
core domain and a smaller, largely
"lid." Four extended polypeptide segments connect these two domains. Dimerization of LacC occurs via interactions between lid domains, which come together to form a
-clasp structure. Residues from both subunits contribute to substrate binding. LacC adopts a closed structure required for phosphoryl transfer only when both substrate and co-factor are bound. A reaction mechanism similar to that used by other phosphoryl transferases is proposed, although unusually, when both substrate and co-factor are bound to the enzyme two Mg2+ ions are observed in the active site. A new motif of amino acid sequence conservation common to the pfkB subfamily of carbohydrate kinases is identified.
Received for publication, February 20, 2007 , and in revised form, April 6, 2007.
The atomic coordinates and structure factors (code 2JGV and 2JG1) 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 Supported by the Wellcome Trust and the Biotechnology and Biological Sciences Research Council (Structural Proteomics of Rational Targets).
2 To whom correspondence should be addressed: Macomolecular Crystallography Group, European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble Cedex, France. Tel.: 33-4-76-88-23-94; Fax: 33-4-76-88-29-04; E-mail: leonard{at}esrf.fr.
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