1SKU

E. coli Aspartate Transcarbamylase 240's Loop Mutant (K244N)


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.231 
  • R-Value Work: 0.201 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

240s Loop Interactions Stabilize the T State of Escherichia coli Aspartate Transcarbamoylase.

Alam, N.Stieglitz, K.A.Caban, M.D.Gourinath, S.Tsuruta, H.Kantrowitz, E.R.

(2004) J.Biol.Chem. 279: 23302-23310

  • DOI: 10.1074/jbc.M401637200

  • PubMed Abstract: 
  • Here the functional and structural importance of interactions involving the 240s loop of the catalytic chain for the stabilization of the T state of aspartate transcarbamoylase were tested by replacement of Lys-244 with Asn and Ala. For the K244A and ...

    Here the functional and structural importance of interactions involving the 240s loop of the catalytic chain for the stabilization of the T state of aspartate transcarbamoylase were tested by replacement of Lys-244 with Asn and Ala. For the K244A and K244N mutant enzymes, the aspartate concentration required to achieve half-maximal specific activity was reduced to 8.4 and 4.0 mm, respectively, as compared with 12.4 mM for the wild-type enzyme. Both mutant enzymes exhibited dramatic reductions in homotropic cooperativity and the ability of the heterotropic effectors to modulate activity. Small angle x-ray scattering studies showed that the unligated structure of the mutant enzymes, and the structure of the mutant enzymes ligated with N-phosphonacetyl-L-aspartate, were similar to that observed for the unligated and N-phosphonacetyl-L-aspartateligated wild-type enzyme. A saturating concentration of carbamoyl phosphate alone has little influence on the small angle x-ray scattering of the wild-type enzyme. However, carbamoyl phosphate was able to shift the structure of the two mutant enzymes dramatically toward R, establishing that the mutations had destabilized the T state of the enzyme. The x-ray crystal structure of K244N enzyme showed that numerous local T state stabilizing interactions involving 240s loop residues were lost. Furthermore, the structure established that the mutation induced additional alterations at the subunit interfaces, the active site, the relative position of the domains of the catalytic chains, and the allosteric domain of the regulatory chains. Most of these changes reflect motions toward the R state structure. However, the K244N mutation alone only changes local conformations of the enzyme to an R-like structure, without triggering the quaternary structural transition. These results suggest that loss of cooperativity and reduction in heterotropic effects is due to the dramatic destabilization of the T state of the enzyme by this mutation in the 240s loop of the catalytic chain.


    Organizational Affiliation

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




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Aspartate carbamoyltransferase catalytic chain
A, C
310Escherichia coli (strain K12)Mutation(s): 1 
Gene Names: pyrB
EC: 2.1.3.2
Find proteins for P0A786 (Escherichia coli (strain K12))
Go to UniProtKB:  P0A786
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Aspartate carbamoyltransferase regulatory chain
B, D
153Escherichia coli (strain K12)Mutation(s): 0 
Gene Names: pyrI
Find proteins for P0A7F3 (Escherichia coli (strain K12))
Go to UniProtKB:  P0A7F3
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
ZN
Query on ZN

Download SDF File 
Download CCD File 
B, D
ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
MLI
Query on MLI

Download SDF File 
Download CCD File 
A, C
MALONATE ION
C3 H2 O4
OFOBLEOULBTSOW-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.231 
  • R-Value Work: 0.201 
  • Space Group: H 3
Unit Cell:
Length (Å)Angle (°)
a = 125.670α = 90.00
b = 125.670β = 90.00
c = 198.200γ = 120.00
Software Package:
Software NamePurpose
AMoREphasing
DENZOdata reduction
SCALEPACKdata scaling
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2004-03-30
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Advisory, Derived calculations, Version format compliance