1TU0: Aspartate Transcarbamoylase Catalytic Chain Mutant E50a Complex With Phosphonoacetamide

A detailed description of the transition that allosteric enzymes undergo constitutes a major challenge in structural biology. We have succeeded in trapping four distinct allosteric states of a mutant enzyme of Escherichia coli aspartate transcarbomylase and determining their structures by X-ray crystallography. The mutant version of aspartate transcarbamoylase in which Glu50 in the catalytic chains was replaced by Ala destabilizes the native R state and shifts the equilibrium towards the T state. This behavior allowed the use of substrate analogs such as phosphonoacetamide and malonate to trap the enzyme in T-like and R-like structures that are distinct from the T-state structure of the wild-type enzyme (as represented by the structure of the enzyme with CTP bound and the R-state structure as represented by the structure with N-(phosphonacetyl)-L-aspartate bound). These structures shed light on the nature and the order of internal structural rearrangements during the transition from the T to the R state. They also suggest an explanation for diminished activity of the E50A enzyme and for the change in reaction mechanism from ordered to random for this mutant enzyme.
PDB ID: 1TU0Download
MMDB ID: 28719
PDB Deposition Date: 2004/6/23
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.55  Å
Source Organism:
Similar Structures:
Biological Unit for 1TU0: dodecameric; determined by author and by software (PISA,PQS)
Molecular Components in 1TU0
Label Count Molecule
Proteins (12 molecules)
Aspartate Carbamoyltransferase Catalytic Chain(Gene symbol: pyrB)
Molecule annotation
Aspartate Carbamoyltransferase Regulatory Chain(Gene symbol: pyrI)
Molecule annotation
Chemicals (12 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB