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| [[Image:3csu.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_3csu| PDB=3csu | SCENE= }} | | {{STRUCTURE_3csu| PDB=3csu | SCENE= }} |
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| '''CATALYTIC TRIMER OF ESCHERICHIA COLI ASPARTATE TRANSCARBAMOYLASE'''
| | ===CATALYTIC TRIMER OF ESCHERICHIA COLI ASPARTATE TRANSCARBAMOYLASE=== |
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| ==Overview==
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| The lack of knowledge of the three-dimensional structure of the trimeric, catalytic (C) subunit of aspartate transcarbamoylase (ATCase) has impeded understanding of the allosteric regulation of this enzyme and left unresolved the mechanism by which the active, unregulated C trimers are inactivated on incorporation into the unliganded (taut or T state) holoenzyme. Surprisingly, the isolated C trimer, based on the 1.9-A crystal structure reported here, resembles more closely the trimers in the T state enzyme than in the holoenzyme:bisubstrate-analog complex, which has been considered as the active, relaxed (R) state enzyme. Unlike the C trimer in either the T state or bisubstrate-analog-bound holoenzyme, the isolated C trimer lacks 3-fold symmetry, and the active sites are partially disordered. The flexibility of the C trimer, contrasted to the highly constrained T state ATCase, suggests that regulation of the holoenzyme involves modulating the potential for conformational changes essential for catalysis. Large differences in structure between the active C trimer and the holoenzyme:bisubstrate-analog complex call into question the view that this complex represents the activated R state of ATCase. | | The line below this paragraph, {{ABSTRACT_PUBMED_10318893}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10318893 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10318893}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Endrizzi, J A.]] | | [[Category: Endrizzi, J A.]] |
| [[Category: Schachman, H K.]] | | [[Category: Schachman, H K.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 21:58:45 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 13:06:26 2008'' |