1F1B

CRYSTAL STRUCTURE OF E. COLI ASPARTATE TRANSCARBAMOYLASE P268A MUTANT IN THE R-STATE IN THE PRESENCE OF N-PHOSPHONACETYL-L-ASPARTATE

Summary for 1F1B

• Entry DOI: 10.2210/pdb1f1b/pdb
• Related: 1D09 1EZZ 6at1
• Descriptor: ASPARTATE CARBAMOYLTRANSFERASE CATALYTIC CHAIN, ASPARTATE CARBAMOYLTRANSFERASE REGULATORY CHAIN, N-(PHOSPHONACETYL)-L-ASPARTIC ACID, ... (5 entities in total)
• Functional Keywords: aspartate transcarbamoylase, aspartate carbamoyltransferase, cis-proline, cis-amino acid, transferase
• Biological source: Escherichia coli; More
• Total number of polymer chains: 4
• Total formula weight: 103550.45

Authors

Jin, L.,Stec, B.,Kantrowitz, E.R. (deposition date: 2000-05-18, release date: 2000-11-22, Last modification date: 2024-02-07)

Primary citation

Jin, L.,Stec, B.,Kantrowitz, E.R.
A cis-proline to alanine mutant of E. coli aspartate transcarbamoylase: kinetic studies and three-dimensional crystal structures.
Biochemistry, 39:8058-8066, 2000

PubMed Abstract: The only cis-proline residue in Escherichia coli aspartate transcarbamoylase has been replaced by alanine using site-specific mutagenesis.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.

PubMed: 10891088
DOI: 10.1021/bi000418+

Experimental method

X-RAY DIFFRACTION (2.3 Å)