Structures of Staphylococcus aureus D-tagatose-6-phosphate kinase implicate domain motions in specificity and mechanism.
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 alpha/beta core domain and a smaller, largely beta "lid." Four extended polypeptide segments connect these two domains. Dimerization of LacC occurs via interactions between lid domains, which come together to form a beta-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 Mg(2+) 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.
Miallau
Linda
L
Macromolecular Crystallography Group, European Synchrotron Radiation Facility, 38043 Grenoble, France.
Hunter
William N
WN
McSweeney
Sean M
SM
Leonard
Gordon A
GA
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000737:chemistry*; D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D003067:Coenzymes / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013211:Staphylococcus aureus / Q000201:enzymology*
D001426:Bacterial Proteins; D003067:Coenzymes; D000244:Adenosine Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C432824:tagatose 6-phosphate kinase; D008274:Magnesium