1P18

Hypoxanthine Phosphoribosyltransferase from Trypanosoma cruzi, K68R mutant, ternary substrates complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.293 
  • R-Value Work: 0.210 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Interactions at the dimer interface influence the relative efficiencies for purine nucleotide synthesis and pyrophosphorolysis in a phosphoribosyltransferase

Canyuk, B.Medrano, F.J.Wenck, M.A.Focia, P.J.Eakin, A.E.Craig III, S.P.

(2004) J.Mol.Biol. 335: 905-921

  • Primary Citation of Related Structures:  1P17, 1P19

  • PubMed Abstract: 
  • Enzymes that salvage 6-oxopurines, including hypoxanthine phosphoribosyltransferases (HPRTs), are potential targets for drugs in the treatment of diseases caused by protozoan parasites. For this reason, a number of high-resolution X-ray crystal struc ...

    Enzymes that salvage 6-oxopurines, including hypoxanthine phosphoribosyltransferases (HPRTs), are potential targets for drugs in the treatment of diseases caused by protozoan parasites. For this reason, a number of high-resolution X-ray crystal structures of the HPRTs from protozoa have been reported. Although these structures did not reveal why HPRTs need to form dimers for catalysis, they revealed the existence of potentially relevant interactions involving residues in a loop of amino acid residues adjacent to the dimer interface, but the contributions of these interactions to catalysis remained poorly understood. The loop, referred to as active-site loop I, contains an unusual non-proline cis-peptide and is composed of residues that are structurally analogous with Leu67, Lys68, and Gly69 in the human HPRT. Functional analyses of site-directed mutations (K68D, K68E, K68N, K68P, and K68R) in the HPRT from Trypanosoma cruzi, etiologic agent of Chagas' disease, show that the side-chain at position 68 can differentially influence the K(m) values for all four substrates as well as the k(cat) values for both IMP formation and pyrophosphorolysis. Also, the results for the K68P mutant are inconsistent with a cis-trans peptide isomerization-assisted catalytic mechanism. These data, together with the results of structural studies of the K68R mutant, reveal that the side-chain of residue 68 does not participate directly in reaction chemistry, but it strongly influences the relative efficiencies for IMP formation and pyrophosphorolysis, and the prevalence of lysine at position 68 in the HPRT of the majority of eukaryotes is consistent with there being a biological role for nucleotide pyrophosphorolysis.


    Organizational Affiliation

    University of North Carolina School of Pharmacy, Chapel Hill, NC 27599, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
hypoxanthine phosphoribosyltransferase
A, B
221Trypanosoma cruzi (strain CL Brener)N/A
Find proteins for Q4DRC4 (Trypanosoma cruzi (strain CL Brener))
Go to UniProtKB:  Q4DRC4
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PRP
Query on PRP

Download SDF File 
Download CCD File 
A, B
ALPHA-PHOSPHORIBOSYLPYROPHOSPHORIC ACID
C5 H13 O14 P3
PQGCEDQWHSBAJP-TXICZTDVSA-N
 Ligand Interaction
MG
Query on MG

Download SDF File 
Download CCD File 
A, B
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
7HP
Query on 7HP

Download SDF File 
Download CCD File 
A, B
7-HYDROXY-PYRAZOLO[4,3-D]PYRIMIDINE
C5 H4 N4 O
JFZSDNLQDTYVEE-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.293 
  • R-Value Work: 0.210 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 39.500α = 90.00
b = 102.100β = 94.30
c = 51.800γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
X-PLORphasing
X-PLORmodel building
X-PLORrefinement
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2004-05-18
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance