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1pb3
From Proteopedia
(New page: 200px<br /><applet load="1pb3" size="450" color="white" frame="true" align="right" spinBox="true" caption="1pb3, resolution 1.70Å" /> '''Sites of binding and...) |
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| - | [[Image:1pb3.jpg|left|200px]]<br /><applet load="1pb3" size=" | + | [[Image:1pb3.jpg|left|200px]]<br /><applet load="1pb3" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1pb3, resolution 1.70Å" /> | caption="1pb3, resolution 1.70Å" /> | ||
'''Sites of binding and orientation in a four location model for protein stereospecificity.'''<br /> | '''Sites of binding and orientation in a four location model for protein stereospecificity.'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The stereospecificity of the enzyme isocitrate dehydrogenase was examined | + | The stereospecificity of the enzyme isocitrate dehydrogenase was examined by steady-state kinetics and x-ray crystallography. The enzyme has the intriguing property that the apoenzyme in the absence of divalent metal showed a selectivity for the inactive l-enantiomer of the substrate isocitrate, whereas the enzyme containing magnesium showed selectivity for the physiologically active d-enantiomer. The hydrogen atom on the C2 carbon that is transferred during the reaction was, in both the d- and l-isocitrate complexes, in an orientation very close to that expected for delivery of a hydride ion to the cosubstrate NADP+. The beta-carboxylate that is eliminated as a CO2 molecule during the reaction occupied the same site on the protein in both the d- and l-isocitrate complexes. In addition, the C3 carbon was in the same protein site in both the d- and l-enantiomers. Only the fourth group, the OH atom, was in a very different position in the apo enzyme and in the metal-containing complexes. A four-location model is necessary to explain the enantiomeric specificity of IDH in contrast to the conventional three-point attachment model. The thermodynamic and kinetic ramifications of this model are explored. |
==About this Structure== | ==About this Structure== | ||
| - | 1PB3 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4 and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Isocitrate_dehydrogenase_(NADP(+)) Isocitrate dehydrogenase (NADP(+))], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.42 1.1.1.42] Full crystallographic information is available from [http:// | + | 1PB3 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Isocitrate_dehydrogenase_(NADP(+)) Isocitrate dehydrogenase (NADP(+))], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.42 1.1.1.42] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1PB3 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Isocitrate dehydrogenase (NADP(+))]] | [[Category: Isocitrate dehydrogenase (NADP(+))]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Jr., D | + | [[Category: Jr., D E.Koshland.]] |
| - | [[Category: Mesecar, A | + | [[Category: Mesecar, A D.]] |
[[Category: GOL]] | [[Category: GOL]] | ||
[[Category: SO4]] | [[Category: SO4]] | ||
| Line 23: | Line 23: | ||
[[Category: stereospecificity]] | [[Category: stereospecificity]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:26:58 2008'' |
Revision as of 12:27, 21 February 2008
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Sites of binding and orientation in a four location model for protein stereospecificity.
Overview
The stereospecificity of the enzyme isocitrate dehydrogenase was examined by steady-state kinetics and x-ray crystallography. The enzyme has the intriguing property that the apoenzyme in the absence of divalent metal showed a selectivity for the inactive l-enantiomer of the substrate isocitrate, whereas the enzyme containing magnesium showed selectivity for the physiologically active d-enantiomer. The hydrogen atom on the C2 carbon that is transferred during the reaction was, in both the d- and l-isocitrate complexes, in an orientation very close to that expected for delivery of a hydride ion to the cosubstrate NADP+. The beta-carboxylate that is eliminated as a CO2 molecule during the reaction occupied the same site on the protein in both the d- and l-isocitrate complexes. In addition, the C3 carbon was in the same protein site in both the d- and l-enantiomers. Only the fourth group, the OH atom, was in a very different position in the apo enzyme and in the metal-containing complexes. A four-location model is necessary to explain the enantiomeric specificity of IDH in contrast to the conventional three-point attachment model. The thermodynamic and kinetic ramifications of this model are explored.
About this Structure
1PB3 is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Isocitrate dehydrogenase (NADP(+)), with EC number 1.1.1.42 Full crystallographic information is available from OCA.
Reference
Sites of binding and orientation in a four-location model for protein stereospecificity., Mesecar AD, Koshland DE Jr, IUBMB Life. 2000 May;49(5):457-66. PMID:10902579
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