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| | {{STRUCTURE_1jt9| PDB=1jt9 | SCENE= }} | | {{STRUCTURE_1jt9| PDB=1jt9 | SCENE= }} |
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| - | '''Structure of the mutant F174A T form of the Glucosamine-6-Phosphate deaminase from E.coli'''
| + | ===Structure of the mutant F174A T form of the Glucosamine-6-Phosphate deaminase from E.coli=== |
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| - | ==Overview==
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| - | The active site of glucosamine-6-phosphate deaminase from Escherichia coli (GlcN6P deaminase, EC 3.5.99.6) has a complex lid formed by two antiparallel beta-strands connected by a helix-loop segment (158-187). This motif contains Arg172, which is a residue involved in binding the substrate in the active-site, and three residues that are part of the allosteric site, Arg158, Lys160 and Thr161. This dual binding role of the motif forming the lid suggests that it plays a key role in the functional coupling between active and allosteric sites. Previous crystallographic work showed that the temperature coefficients of the active-site lid are very large when the enzyme is in its T allosteric state. These coefficients decrease in the R state, thus suggesting that this motif changes its conformational flexibility as a consequence of the allosteric transition. In order to explore the possible connection between the conformational flexibility of the lid and the function of the deaminase, we constructed the site-directed mutant Phe174-Ala. Phe174 is located at the C-end of the lid helix and its side-chain establishes hydrophobic interactions with the remainder of the enzyme. The crystallographic structure of the T state of Phe174-Ala deaminase, determined at 2.02 A resolution, shows no density for the segment 162-181, which is part of the active-site lid (PDB 1JT9). This mutant form of the enzyme is essentially inactive in the absence of the allosteric activator, N-acetylglucosamine-6-P although it recovers its activity up to the wild-type level in the presence of this ligand. Spectrometric and binding studies show that inactivity is due to the inability of the active-site to bind ligands when the allosteric site is empty. These data indicate that the conformational flexibility of the active-site lid critically alters the binding properties of the active site, and that the occupation of the allosteric site restores the lid conformational flexibility to a functional state. | + | The line below this paragraph, {{ABSTRACT_PUBMED_12051945}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 12051945 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_12051945}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Entropic effect]] | | [[Category: Entropic effect]] |
| | [[Category: Structural flexibility]] | | [[Category: Structural flexibility]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 21:53:21 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 20:46:03 2008'' |
Revision as of 17:46, 1 July 2008
Template:STRUCTURE 1jt9
Structure of the mutant F174A T form of the Glucosamine-6-Phosphate deaminase from E.coli
Template:ABSTRACT PUBMED 12051945
About this Structure
1JT9 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
On the role of the conformational flexibility of the active-site lid on the allosteric kinetics of glucosamine-6-phosphate deaminase., Bustos-Jaimes I, Sosa-Peinado A, Rudino-Pinera E, Horjales E, Calcagno ML, J Mol Biol. 2002 May 24;319(1):183-9. PMID:12051945
Page seeded by OCA on Tue Jul 1 20:46:03 2008
