2QII

Crystal Structure Of tRNA-Guanine Transglycosylase (TGT) From Zymomonas mobilis Complexed With Archaeosine Precursor, Preq0


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.7 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.166 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Glutamate versus glutamine exchange swaps substrate selectivity in tRNA-guanine transglycosylase: insight into the regulation of substrate selectivity by kinetic and crystallographic studies.

Tidten, N.Stengl, B.Heine, A.Garcia, G.A.Klebe, G.Reuter, K.

(2007) J.Mol.Biol. 374: 764-776

  • DOI: 10.1016/j.jmb.2007.09.062
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Bacterial tRNA-guanine transglycosylase (Tgt) catalyses the exchange of guanine in the wobble position of particular tRNAs by the modified base preQ(1). In vitro, however, the enzyme is also able to insert the immediate biosynthetic precursor, preQ(0 ...

    Bacterial tRNA-guanine transglycosylase (Tgt) catalyses the exchange of guanine in the wobble position of particular tRNAs by the modified base preQ(1). In vitro, however, the enzyme is also able to insert the immediate biosynthetic precursor, preQ(0), into those tRNAs. This substrate promiscuity is based on a peptide switch in the active site, gated by the general acid/base Glu235. The switch alters the properties of the binding pocket to allow either the accommodation of guanine or preQ(1). The peptide conformer recognising guanine, however, is also able to bind preQ(0). To investigate selectivity regulation, kinetic data for Zymomonas mobilis Tgt were recorded. They show that selectivity in favour of the actual substrate preQ(1) over preQ(0) is not achieved by a difference in affinity but via a higher turnover rate. Moreover, a Tgt(Glu235Gln) variant was constructed. The mutation was intended to stabilise the peptide switch in the conformation favouring guanine and preQ(0) binding. Kinetic characterisation of the mutated enzyme revealed that the Glu235Gln exchange has, with respect to all substrate bases, no significant influence on k(cat). In contrast, K(M)(preQ(1)) is drastically increased, while K(M)(preQ(0)) seems to be decreased. Hence, regarding k(cat)/K(M) as an indicator for catalytic efficiency, selectivity of Tgt in favour of preQ(1) is abolished or even inverted in favour of preQ(0) for Tgt(Glu235Gln). Crystal structures of the mutated enzyme confirm that the mutation strongly favours the binding pocket conformation required for the accommodation of guanine and preQ(0). The way this is achieved, however, significantly differs from that predicted based on crystal structures of wild-type Tgt.


    Organizational Affiliation

    Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Queuine tRNA-ribosyltransferase
A
386Zymomonas mobilis subsp. mobilis (strain ATCC 31821 / ZM4 / CP4)Mutation(s): 0 
Gene Names: tgt
EC: 2.4.2.29
Find proteins for P28720 (Zymomonas mobilis subsp. mobilis (strain ATCC 31821 / ZM4 / CP4))
Go to UniProtKB:  P28720
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PQ0
Query on PQ0

Download SDF File 
Download CCD File 
A
2-AMINO-4-OXO-4,7-DIHYDRO-3H-PYRROLO[2,3-D]PYRIMIDINE-5-CARBONITRILE
7-DEAZA-7-CYANO-GUANINE
C7 H5 N5 O
FMKSMYDYKXQYRV-UHFFFAOYSA-N
 Ligand Interaction
ZN
Query on ZN

Download SDF File 
Download CCD File 
A
ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
GOL
Query on GOL

Download SDF File 
Download CCD File 
A
GLYCEROL
GLYCERIN; PROPANE-1,2,3-TRIOL
C3 H8 O3
PEDCQBHIVMGVHV-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.7 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.166 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 90.622α = 90.00
b = 65.535β = 96.47
c = 70.325γ = 90.00
Software Package:
Software NamePurpose
SHELXL-97refinement
DENZOdata reduction
SCALEPACKdata scaling
CNSphasing
SHELXmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2007-07-17
    Type: Initial release
  • Version 1.1: 2008-05-01
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance