1csh
From Proteopedia
(New page: 200px<br /><applet load="1csh" size="450" color="white" frame="true" align="right" spinBox="true" caption="1csh, resolution 1.65Å" /> '''A VERY SHORT HYDROGE...) |
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| - | [[Image:1csh.jpg|left|200px]]<br /><applet load="1csh" size=" | + | [[Image:1csh.jpg|left|200px]]<br /><applet load="1csh" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1csh, resolution 1.65Å" /> | caption="1csh, resolution 1.65Å" /> | ||
'''A VERY SHORT HYDROGEN BOND PROVIDES ONLY MODERATE STABILIZATION OF AN ENZYME: INHIBITOR COMPLEX OF CITRATE SYNTHASE'''<br /> | '''A VERY SHORT HYDROGEN BOND PROVIDES ONLY MODERATE STABILIZATION OF AN ENZYME: INHIBITOR COMPLEX OF CITRATE SYNTHASE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Two extremely potent inhibitors of citrate synthase, carboxyl and primary | + | Two extremely potent inhibitors of citrate synthase, carboxyl and primary amide analogues of acetyl coenzyme A, have been synthesized. The ternary complexes of these inhibitors with oxaloacetate and citrate synthase have been crystallized and their structures analyzed at 1.70- and 1.65-A resolution, respectively. The inhibitors have dissociation constants in the nanomolar range, with the carboxyl analogue binding more tightly (Ki = 1.6 nM at pH 6.0) than the amide analogue (28 nM), despite the unfavorable requirement for proton uptake by the former. The carboxyl group forms a shorter hydrogen bond with the catalytic Asp 375 (distance < 2.4 A) than does the amide group (distance approximately 2.5 A). Particularly with the carboxylate inhibitor, the very short hydrogen bond distances measured suggest a low barrier or short strong hydrogen bond. However, the binding constants differ by only a factor of 20 at pH 6.0, corresponding to an increase in binding energy for the carboxyl analogue on the enzyme of about 2 kcal/mol more than the amide analogue, much less than has been proposed for short strong hydrogen bonds based on gas phase measurements [> 20 kcal/mol (Gerlt & Gassman, 1993a,b)]. The inhibitor complexes support proposals that Asp 375 and His 274 work in concert to form an enolized form of acetyl-coenzyme A as the first step in the reaction. |
==About this Structure== | ==About this Structure== | ||
| - | 1CSH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with OAA and AMX as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Citrate_(Si)-synthase Citrate (Si)-synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.3.1 2.3.3.1] Full crystallographic information is available from [http:// | + | 1CSH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with <scene name='pdbligand=OAA:'>OAA</scene> and <scene name='pdbligand=AMX:'>AMX</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Citrate_(Si)-synthase Citrate (Si)-synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.3.1 2.3.3.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1CSH OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Gallus gallus]] | [[Category: Gallus gallus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Remington, S | + | [[Category: Remington, S J.]] |
| - | [[Category: Usher, K | + | [[Category: Usher, K C.]] |
[[Category: AMX]] | [[Category: AMX]] | ||
[[Category: OAA]] | [[Category: OAA]] | ||
[[Category: lyase(oxo-acid)]] | [[Category: lyase(oxo-acid)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:09:15 2008'' |
Revision as of 10:09, 21 February 2008
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A VERY SHORT HYDROGEN BOND PROVIDES ONLY MODERATE STABILIZATION OF AN ENZYME: INHIBITOR COMPLEX OF CITRATE SYNTHASE
Overview
Two extremely potent inhibitors of citrate synthase, carboxyl and primary amide analogues of acetyl coenzyme A, have been synthesized. The ternary complexes of these inhibitors with oxaloacetate and citrate synthase have been crystallized and their structures analyzed at 1.70- and 1.65-A resolution, respectively. The inhibitors have dissociation constants in the nanomolar range, with the carboxyl analogue binding more tightly (Ki = 1.6 nM at pH 6.0) than the amide analogue (28 nM), despite the unfavorable requirement for proton uptake by the former. The carboxyl group forms a shorter hydrogen bond with the catalytic Asp 375 (distance < 2.4 A) than does the amide group (distance approximately 2.5 A). Particularly with the carboxylate inhibitor, the very short hydrogen bond distances measured suggest a low barrier or short strong hydrogen bond. However, the binding constants differ by only a factor of 20 at pH 6.0, corresponding to an increase in binding energy for the carboxyl analogue on the enzyme of about 2 kcal/mol more than the amide analogue, much less than has been proposed for short strong hydrogen bonds based on gas phase measurements [> 20 kcal/mol (Gerlt & Gassman, 1993a,b)]. The inhibitor complexes support proposals that Asp 375 and His 274 work in concert to form an enolized form of acetyl-coenzyme A as the first step in the reaction.
About this Structure
1CSH is a Single protein structure of sequence from Gallus gallus with and as ligands. Active as Citrate (Si)-synthase, with EC number 2.3.3.1 Full crystallographic information is available from OCA.
Reference
A very short hydrogen bond provides only moderate stabilization of an enzyme-inhibitor complex of citrate synthase., Usher KC, Remington SJ, Martin DP, Drueckhammer DG, Biochemistry. 1994 Jun 28;33(25):7753-9. PMID:8011640
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