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| {{STRUCTURE_1xge| PDB=1xge | SCENE= }} | | {{STRUCTURE_1xge| PDB=1xge | SCENE= }} |
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| '''Dihydroorotase from Escherichia coli: Loop Movement and Cooperativity between subunits'''
| | ===Dihydroorotase from Escherichia coli: Loop Movement and Cooperativity between subunits=== |
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| ==Overview==
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| Escherichia coli dihydroorotase has been crystallized in the presence of the product, L-dihydroorotate (L-DHO), and the structure refined at 1.9A resolution. The structure confirms that previously reported (PDB entry 1J79), crystallized in the presence of the substrate N-carbamyl-D,L-aspartate (D, L-CA-asp), which had a dimer in the asymmetric unit, with one subunit having the substrate, L-CA-asp bound at the active site and the other having L-DHO. Importantly, no explanation for the unusual structure was given. Our results now show that a loop comprised of residues 105-115 has different conformations in the two subunits. In the case of the L-CA-asp-bound subunit, this loop reaches in toward the active site and makes hydrogen-bonding contact with the bound substrate molecule. For the L-DHO-bound subunit, the loop faces in the opposite direction and forms part of the surface of the protein. Analysis of the kinetics for conversion of L-DHO to L-CA-asp at low concentrations of L-DHO shows positive cooperativity with a Hill coefficient n=1.57(+/-0.13). Communication between subunits in the dimer may occur via cooperative conformational changes of the side-chains of a tripeptide from each subunit: Arg256-His257-Arg258, near the subunit interface.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15826651}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15826651 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15826651}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Maher, M J.]] | | [[Category: Maher, M J.]] |
| [[Category: Tim barrel]] | | [[Category: Tim barrel]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 14:59:45 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 15:45:59 2008'' |
