PMID:17123542
| Citation |
Di Luccio, E, Petschacher, B, Voegtli, J, Chou, HT, Stahlberg, H, Nidetzky, B and Wilson, DK (2007) Structural and kinetic studies of induced fit in xylulose kinase from Escherichia coli. J. Mol. Biol. 365:783-98 |
|---|---|
| Abstract |
The primary metabolic route for D-xylose, the second most abundant sugar in nature, is via the pentose phosphate pathway after a two-step or three-step conversion to xylulose-5-phosphate. Xylulose kinase (XK; EC 2.7.1.17) phosphorylates D-xylulose, the last step in this conversion. The apo and D-xylulose-bound crystal structures of Escherichia coli XK have been determined and show a dimer composed of two domains separated by an open cleft. XK dimerization was observed directly by a cryo-EM reconstruction at 36 A resolution. Kinetic studies reveal that XK has a weak substrate-independent MgATP-hydrolyzing activity, and phosphorylates several sugars and polyols with low catalytic efficiency. Binding of pentulose and MgATP to form the reactive ternary complex is strongly synergistic. Although the steady-state kinetic mechanism of XK is formally random, a path is preferred in which D-xylulose binds before MgATP. Modelling of MgATP binding to XK and the accompanying conformational change suggests that sugar binding is accompanied by a dramatic hinge-bending movement that enhances interactions with MgATP, explaining the observed synergism. A catalytic mechanism is proposed and supported by relevant site-directed mutants. |
| Links |
PubMed PMC1995121 Online version:10.1016/j.jmb.2006.10.068 |
| Keywords |
Adenosine Triphosphatases/chemistry; Amino Acid Sequence; Carbohydrates/chemistry; Catalysis; Conserved Sequence; Cryoelectron Microscopy; Crystallography, X-Ray; Enzyme Inhibitors/pharmacology; Escherichia coli/enzymology; Glycerol Kinase/chemistry; Kinetics; Models, Molecular; Molecular Sequence Data; Phosphotransferases (Alcohol Group Acceptor)/antagonists & inhibitors; Phosphotransferases (Alcohol Group Acceptor)/chemistry; Phosphotransferases (Alcohol Group Acceptor)/metabolism; Phosphotransferases (Alcohol Group Acceptor)/ultrastructure; Protein Structure, Quaternary; Protein Structure, Secondary; Sequence Alignment; Substrate Specificity |
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