1JN3

FIDELITY PROPERTIES AND STRUCTURE OF M282L MUTATOR MUTANT OF DNA POLYMERASE: SUBTLE STRUCTURAL CHANGES INFLUENCE THE MECHANISM OF NUCLEOTIDE DISCRIMINATION


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.256 
  • R-Value Work: 0.215 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

A DNA polymerase beta mutator mutant with reduced nucleotide discrimination and increased protein stability

Shah, A.M.Conn, D.A.Li, S.-X.Capaldi, A.Jaeger, J.Sweasy, J.B.

(2001) Biochemistry 40: 11372-11381


  • PubMed Abstract: 
  • DNA polymerase beta (pol beta) offers a simple system to examine the role of polymerase structure in the fidelity of DNA synthesis. In this study, the M282L variant of pol beta (M282Lbeta) was identified using an in vivo genetic screen. Met282, which ...

    DNA polymerase beta (pol beta) offers a simple system to examine the role of polymerase structure in the fidelity of DNA synthesis. In this study, the M282L variant of pol beta (M282Lbeta) was identified using an in vivo genetic screen. Met282, which does not contact the DNA template or the incoming deoxynucleoside triphosphate (dNTP) substrate, is located on alpha-helix N of pol beta. This mutant enzyme demonstrates increased mutagenesis in both in vivo and in vitro assays. M282Lbeta has a 7.5-fold higher mutation frequency than wild-type pol beta; M282Lbeta commits a variety of base substitution and frameshift errors. Transient-state kinetic methods were used to investigate the mechanism of intrinsic mutator activity of M282Lbeta. Results show an 11-fold decrease in dNTP substrate discrimination at the level of ground-state binding. However, during the protein conformational change and/or phosphodiester bond formation, the nucleotide discrimination is improved. X-ray crystallography was utilized to gain insights into the structural basis of the decreased DNA synthesis fidelity. Most of the structural changes are localized to site 282 and the surrounding region in the C-terminal part of the 31-kDa domain. Repositioning of mostly hydrophobic amino acid residues in the core of the C-terminal portion generates a protein with enhanced stability. The combination of structural and equilibrium unfolding data suggests that the mechanism of nucleotide discrimination is possibly affected by the compacting of the hydrophobic core around residue Leu282. Subsequent movement of an adjacent surface residue, Arg283, produces a slight increase in volume of the pocket that may accommodate the incoming correct base pair. The structural changes of M282Lbeta ultimately lead to an overall reduction in polymerase fidelity.


    Organizational Affiliation

    Department of Therapeutic Radiology and Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
DNA POLYMERASE BETA
A
251Rattus norvegicusGene Names: Polb
EC: 2.7.7.7, 4.2.99.-
Find proteins for P06766 (Rattus norvegicus)
Go to UniProtKB:  P06766
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.256 
  • R-Value Work: 0.215 
  • Space Group: P 21 21 2
Unit Cell:
Length (Å)Angle (°)
a = 119.540α = 90.00
b = 63.620β = 90.00
c = 37.510γ = 90.00
Software Package:
Software NamePurpose
CNSphasing
SCALEPACKdata scaling
DENZOdata reduction
CNSrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-08-03
    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: 2011-11-16
    Type: Atomic model