1ezz
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(New page: 200px<br /><applet load="1ezz" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ezz, resolution 2.7Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 12:21, 20 November 2007
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CRYSTAL STRUCTURE OF E. COLI ASPARTATE TRANSCARBAMOYLASE P268A MUTANT IN THE T-STATE
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The only cis-proline residue in Escherichia coli aspartate, transcarbamoylase has been replaced by alanine using site-specific, mutagenesis.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
1EZZ is a Protein complex structure of sequences from Escherichia coli with ZN as ligand. Active as Aspartate carbamoyltransferase, with EC number 2.1.3.2 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
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