1ozf
From Proteopedia
(New page: 200px<br /><applet load="1ozf" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ozf, resolution 2.30Å" /> '''The crystal structur...) |
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| - | [[Image:1ozf.jpg|left|200px]]<br /><applet load="1ozf" size=" | + | [[Image:1ozf.jpg|left|200px]]<br /><applet load="1ozf" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1ozf, resolution 2.30Å" /> | caption="1ozf, resolution 2.30Å" /> | ||
'''The crystal structure of Klebsiella pneumoniae acetolactate synthase with enzyme-bound cofactors'''<br /> | '''The crystal structure of Klebsiella pneumoniae acetolactate synthase with enzyme-bound cofactors'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Acetohydroxyacid synthase (AHAS) and acetolactate synthase (ALS) are | + | Acetohydroxyacid synthase (AHAS) and acetolactate synthase (ALS) are thiamine diphosphate (ThDP)-dependent enzymes that catalyze the decarboxylation of pyruvate to give a cofactor-bound hydroxyethyl group, which is transferred to a second molecule of pyruvate to give 2-acetolactate. AHAS is found in plants, fungi, and bacteria, is involved in the biosynthesis of the branched-chain amino acids, and contains non-catalytic FAD. ALS is found only in some bacteria, is a catabolic enzyme required for the butanediol fermentation, and does not contain FAD. Here we report the 2.3-A crystal structure of Klebsiella pneumoniae ALS. The overall structure is similar to AHAS except for a groove that accommodates FAD in AHAS, which is filled with amino acid side chains in ALS. The ThDP cofactor has an unusual conformation that is unprecedented among the 26 known three-dimensional structures of nine ThDP-dependent enzymes, including AHAS. This conformation suggests a novel mechanism for ALS. A second structure, at 2.0 A, is described in which the enzyme is trapped halfway through the catalytic cycle so that it contains the hydroxyethyl intermediate bound to ThDP. The cofactor has a tricyclic structure that has not been observed previously in any ThDP-dependent enzyme, although similar structures are well known for free thiamine. This structure is consistent with our proposed mechanism and probably results from an intramolecular proton transfer within a tricyclic carbanion that is the true reaction intermediate. Modeling of the second molecule of pyruvate into the active site of the enzyme with the bound intermediate is consistent with the stereochemistry and specificity of ALS. |
==About this Structure== | ==About this Structure== | ||
| - | 1OZF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Klebsiella_pneumoniae Klebsiella pneumoniae] with PO4, MG, TPP and PEG as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Acetolactate_synthase Acetolactate synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.2.1.6 2.2.1.6] Full crystallographic information is available from [http:// | + | 1OZF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Klebsiella_pneumoniae Klebsiella pneumoniae] with <scene name='pdbligand=PO4:'>PO4</scene>, <scene name='pdbligand=MG:'>MG</scene>, <scene name='pdbligand=TPP:'>TPP</scene> and <scene name='pdbligand=PEG:'>PEG</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Acetolactate_synthase Acetolactate synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.2.1.6 2.2.1.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1OZF OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Klebsiella pneumoniae]] | [[Category: Klebsiella pneumoniae]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Duggleby, R | + | [[Category: Duggleby, R G.]] |
| - | [[Category: Guddat, L | + | [[Category: Guddat, L W.]] |
| - | [[Category: Pang, S | + | [[Category: Pang, S S.]] |
| - | [[Category: Schowen, R | + | [[Category: Schowen, R L.]] |
[[Category: MG]] | [[Category: MG]] | ||
[[Category: PEG]] | [[Category: PEG]] | ||
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[[Category: thiamin diphosphate]] | [[Category: thiamin diphosphate]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:23:24 2008'' |
Revision as of 12:23, 21 February 2008
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The crystal structure of Klebsiella pneumoniae acetolactate synthase with enzyme-bound cofactors
Overview
Acetohydroxyacid synthase (AHAS) and acetolactate synthase (ALS) are thiamine diphosphate (ThDP)-dependent enzymes that catalyze the decarboxylation of pyruvate to give a cofactor-bound hydroxyethyl group, which is transferred to a second molecule of pyruvate to give 2-acetolactate. AHAS is found in plants, fungi, and bacteria, is involved in the biosynthesis of the branched-chain amino acids, and contains non-catalytic FAD. ALS is found only in some bacteria, is a catabolic enzyme required for the butanediol fermentation, and does not contain FAD. Here we report the 2.3-A crystal structure of Klebsiella pneumoniae ALS. The overall structure is similar to AHAS except for a groove that accommodates FAD in AHAS, which is filled with amino acid side chains in ALS. The ThDP cofactor has an unusual conformation that is unprecedented among the 26 known three-dimensional structures of nine ThDP-dependent enzymes, including AHAS. This conformation suggests a novel mechanism for ALS. A second structure, at 2.0 A, is described in which the enzyme is trapped halfway through the catalytic cycle so that it contains the hydroxyethyl intermediate bound to ThDP. The cofactor has a tricyclic structure that has not been observed previously in any ThDP-dependent enzyme, although similar structures are well known for free thiamine. This structure is consistent with our proposed mechanism and probably results from an intramolecular proton transfer within a tricyclic carbanion that is the true reaction intermediate. Modeling of the second molecule of pyruvate into the active site of the enzyme with the bound intermediate is consistent with the stereochemistry and specificity of ALS.
About this Structure
1OZF is a Single protein structure of sequence from Klebsiella pneumoniae with , , and as ligands. Active as Acetolactate synthase, with EC number 2.2.1.6 Full crystallographic information is available from OCA.
Reference
The crystal structures of Klebsiella pneumoniae acetolactate synthase with enzyme-bound cofactor and with an unusual intermediate., Pang SS, Duggleby RG, Schowen RL, Guddat LW, J Biol Chem. 2004 Jan 16;279(3):2242-53. Epub 2003 Oct 13. PMID:14557277
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