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| | {{STRUCTURE_1cd5| PDB=1cd5 | SCENE= }} | | {{STRUCTURE_1cd5| PDB=1cd5 | SCENE= }} |
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| - | '''GLUCOSAMINE-6-PHOSPHATE DEAMINASE FROM E.COLI, T CONFORMER'''
| + | ===GLUCOSAMINE-6-PHOSPHATE DEAMINASE FROM E.COLI, T CONFORMER=== |
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| - | ==Overview==
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| - | BACKGROUND: The allosteric hexameric enzyme glucosamine-6-phosphate deaminase from Escherichia coli catalyses the regulatory step of N-acetylglucosamine catabolism, which consists of the isomerisation and deamination of glucosamine 6-phosphate (GlcN6P) to form fructose 6-phosphate (Fru6P) and ammonia. The reversibility of the catalysis and its rapid-equilibrium random kinetic mechanism, among other properties, make this enzyme a good model for studying allosteric processes. RESULTS: Here we present the structure of P6(3)22 crystals, obtained in sodium acetate, of GlcN6P deaminase in its ligand-free T state. These crystals are very sensitive to X-ray radiation and have a high (78%) solvent content. The activesite lid (residues 162-185) is highly disordered in the T conformer; this may contribute significantly to the free-energy change of the whole allosteric transition. Comparison of the structure with the crystallographic coordinates of the R conformer (Brookhaven Protein Data Bank entry 1 dea) allows us to describe the geometrical changes associated with the allosteric transition as the movement of two rigid entities within each monomer. The active site, located in a deep cleft between these two rigid entities, presents a more open geometry in the T conformer than in the R conformer. CONCLUSIONS: The differences in active-site geometry are related to alterations in the substrate-binding properties associated with the allosteric transition. The rigid nature of the two mobile structural units of each monomer seems to be essential in order to explain the observed kinetics of the deaminase hexamer. The triggers for both the homotropic and heterotropic allosteric transitions are discussed and particular residues are assigned to these functions. A structural basis for an entropic term in the allosteric transition is an interesting new feature that emerges from this study.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_10378272}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 10378272 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_10378272}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Allosteric enzyme]] | | [[Category: Allosteric enzyme]] |
| | [[Category: Entropic effect]] | | [[Category: Entropic effect]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:36:01 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 20:34:48 2008'' |
Revision as of 17:34, 30 June 2008
Template:STRUCTURE 1cd5
GLUCOSAMINE-6-PHOSPHATE DEAMINASE FROM E.COLI, T CONFORMER
Template:ABSTRACT PUBMED 10378272
About this Structure
1CD5 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
The allosteric transition of glucosamine-6-phosphate deaminase: the structure of the T state at 2.3 A resolution., Horjales E, Altamirano MM, Calcagno ML, Garratt RC, Oliva G, Structure. 1999 May;7(5):527-37. PMID:10378272
Page seeded by OCA on Mon Jun 30 20:34:48 2008
