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| {{STRUCTURE_1f1b| PDB=1f1b | SCENE= }} | | {{STRUCTURE_1f1b| PDB=1f1b | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF E. COLI ASPARTATE TRANSCARBAMOYLASE P268A MUTANT IN THE R-STATE IN THE PRESENCE OF N-PHOSPHONACETYL-L-ASPARTATE'''
| | ===CRYSTAL STRUCTURE OF E. COLI ASPARTATE TRANSCARBAMOYLASE P268A MUTANT IN THE R-STATE IN THE PRESENCE OF N-PHOSPHONACETYL-L-ASPARTATE=== |
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| ==Overview==
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| The only cis-proline residue in Escherichia coli aspartate transcarbamoylase has been replaced by alanine using site-specific mutagenesis. The Pro268-->Ala enzyme exhibits a 40-fold reduction in enzyme activity and decreased substrate affinity toward carbamoyl phosphate and aspartate compared to the corresponding values for the wild-type enzyme. The concentration of the bisubstrate analogue N-phosphonacetyl-L-aspartate (PALA) required to activate the mutant enzyme to the same extent as the wild-type enzyme is significantly increased. The heterotropic effects of ATP and CTP upon the Pro268-->Ala enzyme are also altered. Crystal structures of the Pro268-->Ala enzyme in both T- and R-states show that the cis-peptidyl linkage between Leu267 and Ala268 is maintained. However, the tertiary structure of both the catalytic and regulatory chains has been altered by the amino acid substitution, and the mobility of the active-site residues is increased for the R-state structure of Pro268-->Ala enzyme as comparison with the wild-type R-state structure. These structural changes are responsible for the loss of enzyme activity. Thus, Pro268 is required for the proper positioning of catalytically critical residues in the active site and is important for the formation of the high-activity high-affinity R-state of E. coli aspartate transcarbamoylase.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10891088}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10891088 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10891088}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Cis-amino acid]] | | [[Category: Cis-amino acid]] |
| [[Category: Cis-proline]] | | [[Category: Cis-proline]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 15:46:25 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 02:20:03 2008'' |
