3ETJ

Crystal structure E. coli Purk in complex with Mg, ADP, and Pi


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.6 Å
  • R-Value Free: 0.215 
  • R-Value Work: 0.158 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Structural analysis of the active site geometry of N(5)-Carboxyaminoimidazole ribonucleotide synthetase from Escherichia coli.

Thoden, J.B.Holden, H.M.Firestine, S.M.

(2008) Biochemistry 47: 13346-13353

  • DOI: 10.1021/bi801734z
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • N(5)-Carboxyaminoimidazole ribonucleotide synthetase (N(5)-CAIR synthetase) converts 5-aminoimidazole ribonucleotide (AIR), MgATP, and bicarbonate into N(5)-CAIR, MgADP, and P(i). The enzyme is required for de novo purine biosynthesis in microbes yet ...

    N(5)-Carboxyaminoimidazole ribonucleotide synthetase (N(5)-CAIR synthetase) converts 5-aminoimidazole ribonucleotide (AIR), MgATP, and bicarbonate into N(5)-CAIR, MgADP, and P(i). The enzyme is required for de novo purine biosynthesis in microbes yet is not found in humans suggesting that it represents an ideal and unexplored target for antimicrobial drug design. Here we report the X-ray structures of N(5)-CAIR synthetase from Escherichia coli with either MgATP or MgADP/P(i) bound in the active site cleft. These structures, determined to 1.6-A resolution, provide detailed information regarding the active site geometry before and after ATP hydrolysis. In both structures, two magnesium ions are observed. Each of these is octahedrally coordinated, and the carboxylate side chain of Glu238 bridges them. For the structure of the MgADP/P(i) complex, crystals were grown in the presence of AIR and MgATP. No electron density was observed for AIR, and the electron density corresponding to the nucleotide clearly revealed the presence of ADP and P(i) rather than ATP. The bound P(i) shifts by approximately 3 A relative to the gamma-phosphoryl group of ATP and forms electrostatic interactions with the side chains of Arg242 and His244. Since the reaction mechanism of N(5)-CAIR synthetase is believed to proceed via a carboxyphosphate intermediate, we propose that the location of the inorganic phosphate represents the binding site for stabilization of this reactive species. Using the information derived from the two structures reported here, coupled with molecular modeling, we propose a catalytic mechanism for N(5)-CAIR synthetase.


    Organizational Affiliation

    Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Phosphoribosylaminoimidazole carboxylase ATPase subunit
A, B
355Escherichia coli (strain K12)Mutation(s): 2 
Gene Names: purK
EC: 6.3.4.18
Find proteins for P09029 (Escherichia coli (strain K12))
Go to UniProtKB:  P09029
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PI
Query on PI

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A, B
HYDROGENPHOSPHATE ION
H O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-L
 Ligand Interaction
ADP
Query on ADP

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Download CCD File 
A, B
ADENOSINE-5'-DIPHOSPHATE
C10 H15 N5 O10 P2
XTWYTFMLZFPYCI-KQYNXXCUSA-N
 Ligand Interaction
CL
Query on CL

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Download CCD File 
A
CHLORIDE ION
Cl
VEXZGXHMUGYJMC-UHFFFAOYSA-M
 Ligand Interaction
MG
Query on MG

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Download CCD File 
A, B
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.6 Å
  • R-Value Free: 0.215 
  • R-Value Work: 0.158 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 128.800α = 90.00
b = 70.500β = 124.30
c = 88.700γ = 90.00
Software Package:
Software NamePurpose
HKL-2000data scaling
TNTrefinement
PDB_EXTRACTdata extraction
HKL-2000data collection
HKL-2000data reduction
PHASERphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2008-10-21
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance