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| {{STRUCTURE_1bg0| PDB=1bg0 | SCENE= }} | | {{STRUCTURE_1bg0| PDB=1bg0 | SCENE= }} |
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| '''TRANSITION STATE STRUCTURE OF ARGININE KINASE'''
| | ===TRANSITION STATE STRUCTURE OF ARGININE KINASE=== |
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| ==Overview==
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| Arginine kinase belongs to the family of enzymes, including creatine kinase, that catalyze the buffering of ATP in cells with fluctuating energy requirements and that has been a paradigm for classical enzymological studies. The 1.86-A resolution structure of its transition-state analog complex, reported here, reveals its active site and offers direct evidence for the importance of precise substrate alignment in the catalysis of bimolecular reactions, in contrast to the unimolecular reactions studied previously. In the transition-state analog complex studied here, a nitrate mimics the planar gamma-phosphoryl during associative in-line transfer between ATP and arginine. The active site is unperturbed, and the reactants are not constrained covalently as in a bisubstrate complex, so it is possible to measure how precisely they are pre-aligned by the enzyme. Alignment is exquisite. Entropic effects may contribute to catalysis, but the lone-pair orbitals are also aligned close enough to their optimal trajectories for orbital steering to be a factor during nucleophilic attack. The structure suggests that polarization, strain toward the transition state, and acid-base catalysis also contribute, but, in contrast to unimolecular enzyme reactions, their role appears to be secondary to substrate alignment in this bimolecular reaction.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9671698}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9671698 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9671698}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Transferase]] | | [[Category: Transferase]] |
| [[Category: Transition state analog]] | | [[Category: Transition state analog]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:27:53 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 19:04:51 2008'' |