1B4X

ASPARTATE AMINOTRANSFERASE FROM E. COLI, C191S MUTATION, WITH BOUND MALEATE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.45 Å
  • R-Value Work: 0.207 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

The role of residues outside the active site: structural basis for function of C191 mutants of Escherichia coli aspartate aminotransferase.

Jeffery, C.J.Gloss, L.M.Petsko, G.A.Ringe, D.

(2000) Protein Eng. 13: 105-112

  • Primary Citation of Related Structures:  1QIR, 1QIS, 1QIT, 5EAA

  • PubMed Abstract: 
  • In previous kinetic studies of Escherichia coli aspartate aminotransferase, it was determined that some substitutions of conserved cysteine 191, which is located outside of the active site, altered the kinetic parameters of the enzyme (Gloss,L.M., Sp ...

    In previous kinetic studies of Escherichia coli aspartate aminotransferase, it was determined that some substitutions of conserved cysteine 191, which is located outside of the active site, altered the kinetic parameters of the enzyme (Gloss,L.M., Spencer,D. E. and Kirsch,J.F., 1996, Protein Struct. Funct. Genet., 24, 195-208). The mutations resulted in an alkaline shift of 0.6-0.8 pH units for the pK(a) of the internal aldimine between the PLP cofactor and Lys258. The change in the pK(a) affected the pH dependence of the k(cat)/K(m) (aspartate) values for the mutant enzymes. To help to understand these observations, crystal structures of five mutant forms of E.coli aspartate aminotransferase (the maleate complexes of C191S, C191F, C191Y and C191W, and C191S without maleate) were determined at about 2 A resolution in the presence of the pyridoxal phosphate cofactor. The overall three-dimensional fold of each mutant enzyme is the same as that of the wild-type protein, but there is a rotation of the mutated side chain around its C(alpha)-C(beta) bond. This side chain rotation results in a change in the pattern of hydrogen bonding connecting the mutant residue and the protonated Schiff base of the cofactor, which could account for the altered pK(a) of the Schiff base imine nitrogen that was reported previously. These results demonstrate how residues outside the active site can be important in helping determine the subtleties of the active site amino acid geometries and interactions and how mutations outside the active site can have effects on catalysis. In addition, these results help explain the surprising result previously reported that, for some mutant proteins, replacement of a buried cysteine with an aromatic side chain did not destabilize the protein fold. Instead, rotation around the C(alpha)-C(beta) bond allowed each large aromatic side chain to become buried in a nearby pocket without large changes in the enzyme's backbone geometry.


    Organizational Affiliation

    Rosenstiel Basic Medical Sciences Research Center, MS029, Brandeis University, Waltham, MA 02454-9110, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
ASPARTATE AMINOTRANSFERASE
A
396Escherichia coli (strain K12)Gene Names: aspC
EC: 2.6.1.1
Find proteins for P00509 (Escherichia coli (strain K12))
Go to UniProtKB:  P00509
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MAE
Query on MAE

Download SDF File 
Download CCD File 
A
MALEIC ACID
C4 H4 O4
VZCYOOQTPOCHFL-UPHRSURJSA-N
 Ligand Interaction
PLP
Query on PLP

Download SDF File 
Download CCD File 
A
PYRIDOXAL-5'-PHOSPHATE
VITAMIN B6 Phosphate
C8 H10 N O6 P
NGVDGCNFYWLIFO-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.45 Å
  • R-Value Work: 0.207 
  • Space Group: C 2 2 21
Unit Cell:
Length (Å)Angle (°)
a = 157.130α = 90.00
b = 86.690β = 90.00
c = 79.870γ = 90.00
Software Package:
Software NamePurpose
R-AXISdata reduction
R-AXISdata scaling
X-PLORphasing
X-PLORmodel building
X-PLORrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2000-10-27
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance