1pb3: Difference between revisions
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'''Sites of binding and orientation in a four location model for protein stereospecificity.''' | '''Sites of binding and orientation in a four location model for protein stereospecificity.''' | ||
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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:[http://www.ncbi.nlm.nih.gov/pubmed/10902579 10902579] | 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:[http://www.ncbi.nlm.nih.gov/pubmed/10902579 10902579] | ||
[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Jr., D E.Koshland.]] | [[Category: Jr., D E.Koshland.]] | ||
[[Category: Mesecar, A D.]] | [[Category: Mesecar, A D.]] | ||
[[Category: | [[Category: Entantiomer]] | ||
[[Category: | [[Category: Isocitrate dehydrogense,idh]] | ||
[[Category: | [[Category: Stereospecificity]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 04:53:46 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 04:53, 3 May 2008
Sites of binding and orientation in a four location model for protein stereospecificity.
OverviewOverview
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 StructureAbout this Structure
1PB3 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
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 Page seeded by OCA on Sat May 3 04:53:46 2008