1DQN

CRYSTAL STRUCTURE OF GIARDIA GUANINE PHOSPHORIBOSYLTRANSFERASE COMPLEXED WITH A TRANSITION STATE ANALOGUE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.75 Å
  • R-Value Free: 0.234 
  • R-Value Work: 0.204 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Crystal structures of Giardia lamblia guanine phosphoribosyltransferase at 1.75 A(,).

Shi, W.Munagala, N.R.Wang, C.C.Li, C.M.Tyler, P.C.Furneaux, R.H.Grubmeyer, C.Schramm, V.L.Almo, S.C.

(2000) Biochemistry 39: 6781-6790

  • Primary Citation of Related Structures:  1DQP

  • PubMed Abstract: 
  • Giardia lamblia, the protozoan parasite responsible for giardiasis, requires purine salvage from its host for RNA and DNA synthesis. G. lamblia expresses an unusual purine phosphoribosyltransferase with a high specificity for guanine (GPRTase). The e ...

    Giardia lamblia, the protozoan parasite responsible for giardiasis, requires purine salvage from its host for RNA and DNA synthesis. G. lamblia expresses an unusual purine phosphoribosyltransferase with a high specificity for guanine (GPRTase). The enzyme's sequence significantly diverges from those of related enzymes in other organisms. The transition state analogue immucillinGP is a powerful inhibitor of HGXPRTase from malaria [Li, C. M., et al. (1999) Nat. Struct. Biol. 6, 582-587] and is also a 10 nM inhibitor of G. lamblia GPRTase. Cocrystallization of GPRTase with immucillinGP led unexpectedly to a GPRTase.immucillinG binary complex with an open catalytic site loop. Diffusion of ligands into preformed crystals gave a GPRTase.immucillinGP.Mg(2+).pyrophosphate complex in which the open loop is stabilized by crystal contacts. G. lamblia GPRTase exhibits substantial structural differences from known purine phosphoribosyltransferases at positions remote from the catalytic site, but conserves most contacts to the bound inhibitor. The filled catalytic site with an open catalytic loop provides insight into ligand binding. One active site Mg(2+) ion is chelated to pyrophosphate, but the other is chelated to two conserved catalytic site carboxylates, suggesting a role for these amino acids. This arrangement of Mg(2+) and pyrophosphate has not been reported in purine phosphoribosyltransferases. ImmucillinG in the binary complex is anchored by its 9-deazaguanine group, and the iminoribitol is disordered. No Mg(2+) or pyrophosphate is detected; thus, the 5'-phosphoryl group is needed to immobilize the iminoribitol prior to magnesium pyrophosphate binding. Filling the catalytic site involves (1) binding the purine ring, (2) anchoring the 5'-phosphate to fix the ribosyl group, (3) binding the first Mg(2+) to Asp125 and Glu126 carboxyl groups and binding Mg(2+).pyrophosphate, and (4) closing the catalytic site loop and formation of bound (Mg(2+))(2). pyrophosphate prior to catalysis. Guanine specificity is provided by two peptide carbonyl oxygens hydrogen-bonded to the exocyclic amino group and a weak interaction to O6. Transition state formation involves N7 protonation by Asp129 acting as the general acid.


    Organizational Affiliation

    Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
GUANINE PHOSPHORIBOSYLTRANSFERASE
A, B
230Giardia intestinalisN/A
Find proteins for Q24973 (Giardia intestinalis)
Go to UniProtKB:  Q24973
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
POP
Query on POP

Download SDF File 
Download CCD File 
A, B
PYROPHOSPHATE 2-
H2 O7 P2
XPPKVPWEQAFLFU-UHFFFAOYSA-L
 Ligand Interaction
MG
Query on MG

Download SDF File 
Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
IMU
Query on IMU

Download SDF File 
Download CCD File 
A, B
PHOSPHORIC ACID MONO-[5-(2-AMINO-4-OXO-4,5-DIHYDRO-3H-PYRROLO[3,2-D]PYRIMIDIN-7-YL)-3,4-DIHYDROXY-PYRROLIDIN-2-YLMETHYL] ESTER
MODIFIED QUANOSINE-5-PHOSPHATE
C11 H16 N5 O7 P
IQLBECLICFDTTF-PVEDRDFWSA-N
 Ligand Interaction
IPA
Query on IPA

Download SDF File 
Download CCD File 
B
ISOPROPYL ALCOHOL
2-PROPANOL
C3 H8 O
KFZMGEQAYNKOFK-UHFFFAOYSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
IMUKi: 10 nM BINDINGMOAD
IMUKi: 10 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.75 Å
  • R-Value Free: 0.234 
  • R-Value Work: 0.204 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 56.632α = 90.00
b = 71.553β = 90.00
c = 123.080γ = 90.00
Software Package:
Software NamePurpose
SOLVEphasing
SCALEPACKdata scaling
DENZOdata reduction
CNSrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2000-07-26
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance