4FYX

E. coli Aspartate Transcarbamoylase complexed with dCTP, UTP, and Mg2+


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.09 Å
  • R-Value Free: 0.212 
  • R-Value Work: 0.165 
  • R-Value Observed: 0.168 

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Ligand Structure Quality Assessment 


This is version 1.1 of the entry. See complete history


Literature

Metal Ion Involvement in the Allosteric Mechanism of Escherichia coli Aspartate Transcarbamoylase.

Cockrell, G.M.Kantrowitz, E.R.

(2012) Biochemistry 51: 7128-7137

  • DOI: 10.1021/bi300920m
  • Primary Citation of Related Structures:  
    4FYV, 4FYW, 4FYX, 4FYY

  • PubMed Abstract: 
  • Escherichia coli aspartate transcarbamoylase (ATCase) allosterically regulates pyrimidine nucleotide biosynthesis. The enzyme is inhibited by CTP and can be further inhibited by UTP, although UTP alone has little or no influence on activity; however, the mechanism for the synergistic inhibition is still unknown ...

    Escherichia coli aspartate transcarbamoylase (ATCase) allosterically regulates pyrimidine nucleotide biosynthesis. The enzyme is inhibited by CTP and can be further inhibited by UTP, although UTP alone has little or no influence on activity; however, the mechanism for the synergistic inhibition is still unknown. To determine how UTP is able to synergistically inhibit ATCase in the presence of CTP, we determined a series of X-ray structures of ATCase·nucleotide complexes. Analysis of the X-ray structures revealed that (1) CTP and dCTP bind in a very similar fashion, (2) UTP, in the presence of dCTP or CTP, binds at a site that does not overlap the CTP/dCTP site, and (3) the triphosphates of the two nucleotides are parallel to each other with a metal ion, in this case Mg(2+), coordinated between the β- and γ-phosphates of the two nucleotides. Kinetic experiments showed that the presence of a metal ion such as Mg(2+) is required for synergistic inhibition. Together, these results explain how the binding of UTP can enhance the binding of CTP and why UTP binds more tightly in the presence of CTP. A mechanism for the synergistic inhibition of ATCase is proposed in which the presence of UTP stabilizes the T state even more than CTP alone. These results also call into question many of the past kinetic and binding experiments with ATCase with nucleotides as the presence of metal contamination was not considered important.


    Organizational Affiliation

    Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Aspartate carbamoyltransferase catalytic chainA, C310Escherichia coli K-12Mutation(s): 0 
Gene Names: pyrBb4245JW4204
EC: 2.1.3.2
UniProt
Find proteins for P0A786 (Escherichia coli (strain K12))
Explore P0A786 
Go to UniProtKB:  P0A786
Protein Feature View
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Aspartate carbamoyltransferase regulatory chainB, D153Escherichia coli K-12Mutation(s): 0 
Gene Names: pyrIb4244JW4203
UniProt
Find proteins for P0A7F3 (Escherichia coli (strain K12))
Explore P0A7F3 
Go to UniProtKB:  P0A7F3
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.09 Å
  • R-Value Free: 0.212 
  • R-Value Work: 0.165 
  • R-Value Observed: 0.168 
  • Space Group: P 3 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 121.21α = 90
b = 121.21β = 90
c = 141.764γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PHENIXrefinement
PDB_EXTRACTdata extraction
HKL-2000data collection
HKL-2000data reduction
HKL-2000data scaling
PHENIXphasing

Structure Validation

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Ligand Structure Quality Assessment  



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-10-10
    Type: Initial release
  • Version 1.1: 2017-11-15
    Changes: Refinement description