1at1
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| , resolution 2.8Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | , and | ||||||
| Activity: | Aspartate carbamoyltransferase, with EC number 2.1.3.2 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
CRYSTAL STRUCTURES OF PHOSPHONOACETAMIDE LIGATED T AND PHOSPHONOACETAMIDE AND MALONATE LIGATED R STATES OF ASPARTATE CARBAMOYLTRANSFERASE AT 2.8-ANGSTROMS RESOLUTION AND NEUTRAL P*H
OverviewOverview
The T----R transition of the cooperative enzyme aspartate carbamoyltransferase occurs at pH 7 in single crystals without visibly cracking many of the crystals and leaving those uncracked suitable for single-crystal X-ray analysis. To promote the T----R transition, we employ the competitive inhibitors of carbamoyl phosphate and aspartate, which are phosphonoacetamide (PAM) and malonate, respectively. In response to PAM binding to the T-state crystals, residues Thr 53-Thr 55 and Pro 266-Pro 268 move to their R-state positions to bind to the phosphonate and amino group of PAM. These changes induce a conformation that can bind tightly the aspartate analogue malonate, which thereby effects the allosteric transition. We prove this by showing that PAM-ligated T-state crystals (Tpam), space group P321 (a = 122.2 A, c = 142.2 A), when transferred to a solution containing 20 mM PAM and 8 mM malonate at pH 7, isomerize to R-state crystals (Rpam,mal,soak), space group also P321 (a = 122.2 A, c = 156.4 A). The R-state structure in which the T----R transition occurs within the crystal at pH 7 compares very well (rms = 0.19 A for all atoms) with an R-state structure determined at pH 7 in which the crystals were initially grown in a solution of PAM and malonate at pH 5.9 and subsequently transferred to a buffer containing the ligands at pH 7 (Rpam,mal,crys). In fact, both of the PAM and malonate ligated R-state structures are very similar to both the carbamoyl phosphate and succinate or the N-(phosphonoacetyl)-L-aspartate ligated structures, even though the R-state structures reported here were determined at pH 7. Crystallographic residuals refined to 0.16-0.18 at 2.8-A resolution for the three structures.
About this StructureAbout this Structure
1AT1 is a Protein complex structure of sequences from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of phosphonoacetamide ligated T and phosphonoacetamide and malonate ligated R states of aspartate carbamoyltransferase at 2.8-A resolution and neutral pH., Gouaux JE, Lipscomb WN, Biochemistry. 1990 Jan 16;29(2):389-402. PMID:2405902
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