1jt9
From Proteopedia
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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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[[Category: Rudino-Pinera, E.]] | [[Category: Rudino-Pinera, E.]] | ||
[[Category: Sosa-Peinado, A.]] | [[Category: Sosa-Peinado, A.]] | ||
| - | [[Category: | + | [[Category: Aldose-ketose isomerase]] |
| - | [[Category: | + | [[Category: Allosteric enzyme]] |
| - | [[Category: | + | [[Category: Entropic effect]] |
| - | [[Category: | + | [[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 | + | |
Revision as of 18:53, 2 May 2008
Structure of the mutant F174A T form of the Glucosamine-6-Phosphate deaminase from E.coli
Overview
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.
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 Fri May 2 21:53:21 2008
