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| {{STRUCTURE_2itm| PDB=2itm | SCENE= }} | | {{STRUCTURE_2itm| PDB=2itm | SCENE= }} |
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| '''Crystal structure of the E. coli xylulose kinase complexed with xylulose'''
| | ===Crystal structure of the E. coli xylulose kinase complexed with xylulose=== |
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| ==Overview==
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| 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. | | The line below this paragraph, {{ABSTRACT_PUBMED_17123542}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17123542 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17123542}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Xylulokinase]] | | [[Category: Xylulokinase]] |
| [[Category: Xylulose]] | | [[Category: Xylulose]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 07:51:16 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 14:05:52 2008'' |
