1K0G

THE CRYSTAL STRUCTURE OF AMINODEOXYCHORISMATE SYNTHASE FROM PHOSPHATE GROWN CRYSTALS


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.238 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Structure of Escherichia coli aminodeoxychorismate synthase: architectural conservation and diversity in chorismate-utilizing enzymes.

Parsons, J.F.Jensen, P.Y.Pachikara, A.S.Howard, A.J.Eisenstein, E.Ladner, J.E.

(2002) Biochemistry 41: 2198-2208

  • Primary Citation of Related Structures:  1K0E

  • PubMed Abstract: 
  • Aminodeoxychorismate synthase is part of a heterodimeric complex that catalyzes the two-step biosynthesis of 4-amino-4-deoxychorismate, a precursor of p-aminobenzoate and folate in microorganisms. In the first step, a glutamine amidotransferase encod ...

    Aminodeoxychorismate synthase is part of a heterodimeric complex that catalyzes the two-step biosynthesis of 4-amino-4-deoxychorismate, a precursor of p-aminobenzoate and folate in microorganisms. In the first step, a glutamine amidotransferase encoded by the pabA gene generates ammonia as a substrate that, along with chorismate, is used in the second step, catalyzed by aminodeoxychorismate synthase, the product of the pabB gene. Here we report the X-ray crystal structure of Escherichia coli PabB determined in two different crystal forms, each at 2.0 A resolution. The 453-residue monomeric PabB has a complex alpha/beta fold which is similar to that seen in the structures of homologous, oligomeric TrpE subunits of several anthranilate synthases of microbial origin. A comparison of the structures of these two classes of chorismate-utilizing enzymes provides a rationale for the differences in quaternary structures seen for these enzymes, and indicates that the weak or transient association of PabB with PabA during catalysis stems at least partly from a limited interface for protein interactions. Additional analyses of the structures enabled the tentative identification of the active site of PabB, which contains a number of residues implicated from previous biochemical and genetic studies to be essential for activity. Differences in the structures determined from phosphate- and formate-grown crystals, and the location of an adventitious formate ion, suggest that conformational changes in loop regions adjacent to the active site may be needed for catalysis. A surprising finding in the structure of PabB was the presence of a tryptophan molecule deeply embedded in a binding pocket that is analogous to the regulatory site in the TrpE subunits of the anthranilate synthases. The strongly bound ligand, which cannot be dissociated without denaturation of PabB, may play a structural role in the enzyme since there is no effect of tryptophan on the enzymic synthesis of aminodeoxychorismate. Extensive sequence similarity in the tryptophan-binding pocket among several other chorismate-utilizing enzymes, including isochorismate synthase, suggests that they too may bind tryptophan for structural integrity, and corroborates early ideas on the evolution of this interesting enzyme family.


    Organizational Affiliation

    Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, National Institute of Standards and Technology, 9600 Gudelsky Drive, Rockville, Maryland 20850, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
p-aminobenzoate synthase component I
A, B
453Escherichia coli (strain K12)Gene Names: pabB
EC: 2.6.1.85
Find proteins for P05041 (Escherichia coli (strain K12))
Go to UniProtKB:  P05041
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PO4
Query on PO4

Download SDF File 
Download CCD File 
A, B
PHOSPHATE ION
O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-K
 Ligand Interaction
TRP
Query on TRP

Download SDF File 
Download CCD File 
A, B
TRYPTOPHAN
C11 H12 N2 O2
QIVBCDIJIAJPQS-VIFPVBQESA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.238 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 102.010α = 90.00
b = 109.710β = 90.00
c = 134.380γ = 90.00
Software Package:
Software NamePurpose
SHELXL-97refinement
X-GENdata scaling
CNSrefinement
MAR345data collection
CNSphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2002-02-27
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2017-10-04
    Type: Refinement description