1f1b
From Proteopedia
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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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[[Category: Kantrowitz, E R.]] | [[Category: Kantrowitz, E R.]] | ||
[[Category: Stec, B.]] | [[Category: Stec, B.]] | ||
| - | [[Category: | + | [[Category: Aspartate carbamoyltransferase]] |
| - | [[Category: | + | [[Category: Aspartate transcarbamoylase]] |
| - | [[Category: | + | [[Category: Cis-amino acid]] |
| - | [[Category: | + | [[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 | + | |
Revision as of 12:46, 2 May 2008
CRYSTAL STRUCTURE OF E. COLI ASPARTATE TRANSCARBAMOYLASE P268A MUTANT IN THE R-STATE IN THE PRESENCE OF N-PHOSPHONACETYL-L-ASPARTATE
Overview
The only cis-proline residue in Escherichia coli aspartate transcarbamoylase has been replaced by alanine using site-specific mutagenesis.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.
About this Structure
1F1B is a Protein complex structure of sequences from Escherichia coli. Full crystallographic information is available from OCA.
Reference
A cis-proline to alanine mutant of E. coli aspartate transcarbamoylase: kinetic studies and three-dimensional crystal structures., Jin L, Stec B, Kantrowitz ER, Biochemistry. 2000 Jul 11;39(27):8058-66. PMID:10891088 Page seeded by OCA on Fri May 2 15:46:25 2008
