8at1
From Proteopedia
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CRYSTAL STRUCTURES OF ASPARTATE CARBAMOYLTRANSFERASE LIGATED WITH PHOSPHONOACETAMIDE, MALONATE, AND CTP OR ATP AT 2.8-ANGSTROMS RESOLUTION AND NEUTRAL P*H
Overview
The R-state structures of the ATP and CTP complexes of aspartate, carbamoyltransferase ligated with phosphonoacetamide and malonate have, been determined at 2.8-A resolution and neutral pH. These structures were, solved by the method of molecular replacement and were refined to, crystallographic residuals between 0.167 and 0.182. The triphosphate, the, ribose, and the purine and pyrimidine moieties of ATP and CTP interact, with similar regions of the allosteric domain of the regulatory dimer. ATP, and CTP relatively increase and decrease the size of the allosteric site, in the vicinity of the base, respectively. For both CTP and ATP at pH 7, the gamma-phosphates are bound to His20 and are also near Lys94, while the, alpha-phosphates interact exclusively with Lys94. The 2'-hydroxyls of both, CTP and ATP are near the amino group of Lys60. The pyrimidine ring of CTP, makes specific hydrogen bonds at the allosteric site: the NH2 group, donates hydrogen bonds to the main-chain carbonyls of Ile12 and Tyr89 and, the pyrimidine ring carbonyl oxygen accepts a hydrogen bond from the amino, group of Lys60; the nitrogen at position 3 in the pyrimidine ring is, hydrogen bonded to a main-chain NH group of Ile12. The purine ring of ATP, also makes numerous interactions with residues at the allosteric site: the, purine NH2 (analogous to the amino group of CTP) donates a hydrogen bond, to the main-chain carbonyl oxygen of Ile12, the N3 nitrogen interacts with, the amino group of Lys60, and the N1 nitrogen hydrogen bonds to the NH, group of Ile12. The binding of CTP and ATP to the allosteric site in the, presence of phosphonoacetamide and malonate does not dramatically alter, the structure of the allosteric binding site or of the allosteric domain., Nonetheless, in the CTP-ligated structure, the average separation between, the catalytic trimers decreases by approximately 0.5 A, indicating a small, shift of the quaternary structure toward the T state. In the CTP- and, ATP-ligated R-state structures, the binding and occupancy of, phosphonoacetamide and malonate are similar and the structures of the, active sites are similar at the current resolution of 2.8 A.
About this Structure
8AT1 is a Protein complex structure of sequences from Escherichia coli with MAL, ZN, PCT and CTP as ligands. Active as Aspartate carbamoyltransferase, with EC number 2.1.3.2 Full crystallographic information is available from OCA.
Reference
Crystal structures of aspartate carbamoyltransferase ligated with phosphonoacetamide, malonate, and CTP or ATP at 2.8-A resolution and neutral pH., Gouaux JE, Stevens RC, Lipscomb WN, Biochemistry. 1990 Aug 21;29(33):7702-15. PMID:2271529
Page seeded by OCA on Tue Nov 20 15:09:49 2007
