2nlx
From Proteopedia
Crystal structure of the apo E. coli xylulose kinase
Overview
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.
About this Structure
2NLX is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Structural and kinetic studies of induced fit in xylulose kinase from Escherichia coli., Di Luccio E, Petschacher B, Voegtli J, Chou HT, Stahlberg H, Nidetzky B, Wilson DK, J Mol Biol. 2007 Jan 19;365(3):783-98. Epub 2006 Oct 25. PMID:17123542 Page seeded by OCA on Sun May 4 09:37:28 2008
