2qut: Difference between revisions
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[[Image:2qut.jpg|left|200px]]<br /><applet load="2qut" size=" | [[Image:2qut.jpg|left|200px]]<br /><applet load="2qut" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="2qut, resolution 1.88Å" /> | caption="2qut, resolution 1.88Å" /> | ||
'''Dihydroxyacetone phosphate enamine intermediate in fructose-1,6-bisphosphate aldolase from rabbit muscle'''<br /> | '''Dihydroxyacetone phosphate enamine intermediate in fructose-1,6-bisphosphate aldolase from rabbit muscle'''<br /> | ||
==Overview== | |||
Class I fructose-1,6-bisphosphate aldolases catalyze the interconversion, between the enamine and iminium covalent enzymatic intermediates by, stereospecific exchange of the pro(S) proton of the, dihydroxyacetone-phosphate C3 carbon, an obligatory reaction step during, substrate cleavage. To investigate the mechanism of stereospecific proton, exchange, high resolution crystal structures of native and a mutant, Lys(146) --> Met aldolase were solved in complex with dihydroxyacetone, phosphate. The structural analysis revealed trapping of the enamine, intermediate at Lys(229) in native aldolase. Mutation of conserved active, site residue Lys(146) to Met drastically decreased activity and enabled, trapping of the putative iminium intermediate in the crystal structure, showing active site attachment by C-terminal residues 360-363. Attachment, positions the conserved C-terminal Tyr(363) hydroxyl within 2.9A of the C3, carbon in the iminium in an orientation consistent with incipient re face, proton transfer. We propose a catalytic mechanism by which the mobile, C-terminal Tyr(363) is activated by the iminium phosphate via a, structurally conserved water molecule to yield a transient phenate, whose, developing negative charge is stabilized by a Lys(146) positive charge, and which abstracts the C3 pro(S) proton forming the enamine. An identical, C-terminal binding mode observed in the presence of phosphate in the, native structure corroborates Tyr(363) interaction with Lys(146) and is, consistent with transient C terminus binding in the enamine. The absence, of charge stabilization and of a mobile C-terminal catalyst explains the, extraordinary stability of enamine intermediates in transaldolases. | |||
==About this Structure== | ==About this Structure== | ||
2QUT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with 13P as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Fructose-bisphosphate_aldolase Fructose-bisphosphate aldolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.2.13 4.1.2.13] Full crystallographic information is available from [http:// | 2QUT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with <scene name='pdbligand=13P:'>13P</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Fructose-bisphosphate_aldolase Fructose-bisphosphate aldolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.2.13 4.1.2.13] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2QUT OCA]. | ||
==Reference== | |||
Stereospecific proton transfer by a mobile catalyst in mammalian fructose-1,6-bisphosphate aldolase., St-Jean M, Sygusch J, J Biol Chem. 2007 Oct 19;282(42):31028-37. Epub 2007 Aug 29. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17728250 17728250] | |||
[[Category: Fructose-bisphosphate aldolase]] | [[Category: Fructose-bisphosphate aldolase]] | ||
[[Category: Oryctolagus cuniculus]] | [[Category: Oryctolagus cuniculus]] | ||
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[[Category: substrate]] | [[Category: substrate]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jan 23 11:57:36 2008'' | ||
