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 Å 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. © 2006 Elsevier Ltd. All rights reserved.
CITATION STYLE
Di Luccio, E., Petschacher, B., Voegtli, J., Chou, H. T., Stahlberg, H., Nidetzky, B., & Wilson, D. K. (2007). Structural and Kinetic Studies of Induced Fit in Xylulose Kinase from Escherichia coli. Journal of Molecular Biology, 365(3), 783–798. https://doi.org/10.1016/j.jmb.2006.10.068
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