1zah
From Proteopedia
(New page: 200px<br /><applet load="1zah" size="450" color="white" frame="true" align="right" spinBox="true" caption="1zah, resolution 1.800Å" /> '''Fructose-1,6-bispho...) |
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| - | [[Image:1zah.gif|left|200px]]<br /><applet load="1zah" size=" | + | [[Image:1zah.gif|left|200px]]<br /><applet load="1zah" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1zah, resolution 1.800Å" /> | caption="1zah, resolution 1.800Å" /> | ||
'''Fructose-1,6-bisphosphate aldolase from rabbit muscle'''<br /> | '''Fructose-1,6-bisphosphate aldolase from rabbit muscle'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Crystal structures were determined to 1.8 A resolution of the glycolytic | + | Crystal structures were determined to 1.8 A resolution of the glycolytic enzyme fructose-1,6-bis(phosphate) aldolase trapped in complex with its substrate and a competitive inhibitor, mannitol-1,6-bis(phosphate). The enzyme substrate complex corresponded to the postulated Schiff base intermediate and has reaction geometry consistent with incipient C3-C4 bond cleavage catalyzed Glu-187, which is adjacent by to the Schiff base forming Lys-229. Atom arrangement about the cleaved bond in the reaction intermediate mimics a pericyclic transition state occurring in nonenzymatic aldol condensations. Lys-146 hydrogen-bonds the substrate C4 hydroxyl and assists substrate cleavage by stabilizing the developing negative charge on the C4 hydroxyl during proton abstraction. Mannitol-1,6-bis(phosphate) forms a noncovalent complex in the active site whose binding geometry mimics the covalent carbinolamine precursor. Glu-187 hydrogen-bonds the C2 hydroxyl of the inhibitor in the enzyme complex, substantiating a proton transfer role by Glu-187 in catalyzing the conversion of the carbinolamine intermediate to Schiff base. Modeling of the acyclic substrate configuration into the active site shows Glu-187, in acid form, hydrogen-bonding both substrate C2 carbonyl and C4 hydroxyl, thereby aligning the substrate ketose for nucleophilic attack by Lys-229. The multifunctional role of Glu-187 epitomizes a canonical mechanistic feature conserved in Schiff base-forming aldolases catalyzing carbohydrate metabolism. Trapping of tagatose-1,6-bis(phosphate), a diastereoisomer of fructose 1,6-bis(phosphate), displayed stereospecific discrimination and reduced ketohexose binding specificity. Each ligand induces homologous conformational changes in two adjacent alpha-helical regions that promote phosphate binding in the active site. |
==About this Structure== | ==About this Structure== | ||
| - | 1ZAH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus]. 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:// | + | 1ZAH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus]. 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=1ZAH OCA]. |
==Reference== | ==Reference== | ||
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[[Category: aldolase]] | [[Category: aldolase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:13:40 2008'' |
Revision as of 14:13, 21 February 2008
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Fructose-1,6-bisphosphate aldolase from rabbit muscle
Overview
Crystal structures were determined to 1.8 A resolution of the glycolytic enzyme fructose-1,6-bis(phosphate) aldolase trapped in complex with its substrate and a competitive inhibitor, mannitol-1,6-bis(phosphate). The enzyme substrate complex corresponded to the postulated Schiff base intermediate and has reaction geometry consistent with incipient C3-C4 bond cleavage catalyzed Glu-187, which is adjacent by to the Schiff base forming Lys-229. Atom arrangement about the cleaved bond in the reaction intermediate mimics a pericyclic transition state occurring in nonenzymatic aldol condensations. Lys-146 hydrogen-bonds the substrate C4 hydroxyl and assists substrate cleavage by stabilizing the developing negative charge on the C4 hydroxyl during proton abstraction. Mannitol-1,6-bis(phosphate) forms a noncovalent complex in the active site whose binding geometry mimics the covalent carbinolamine precursor. Glu-187 hydrogen-bonds the C2 hydroxyl of the inhibitor in the enzyme complex, substantiating a proton transfer role by Glu-187 in catalyzing the conversion of the carbinolamine intermediate to Schiff base. Modeling of the acyclic substrate configuration into the active site shows Glu-187, in acid form, hydrogen-bonding both substrate C2 carbonyl and C4 hydroxyl, thereby aligning the substrate ketose for nucleophilic attack by Lys-229. The multifunctional role of Glu-187 epitomizes a canonical mechanistic feature conserved in Schiff base-forming aldolases catalyzing carbohydrate metabolism. Trapping of tagatose-1,6-bis(phosphate), a diastereoisomer of fructose 1,6-bis(phosphate), displayed stereospecific discrimination and reduced ketohexose binding specificity. Each ligand induces homologous conformational changes in two adjacent alpha-helical regions that promote phosphate binding in the active site.
About this Structure
1ZAH is a Single protein structure of sequence from Oryctolagus cuniculus. Active as Fructose-bisphosphate aldolase, with EC number 4.1.2.13 Full crystallographic information is available from OCA.
Reference
High resolution reaction intermediates of rabbit muscle fructose-1,6-bisphosphate aldolase: substrate cleavage and induced fit., St-Jean M, Lafrance-Vanasse J, Liotard B, Sygusch J, J Biol Chem. 2005 Jul 22;280(29):27262-70. Epub 2005 May 3. PMID:15870069
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