1KRP

DNA polymerase I Klenow fragment (E.C.2.7.7.7) mutant/DNA complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.255 
  • R-Value Work: 0.190 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Structural principles for the inhibition of the 3'-5' exonuclease activity of Escherichia coli DNA polymerase I by phosphorothioates.

Brautigam, C.A.Steitz, T.A.

(1998) J Mol Biol 277: 363-377

  • DOI: 10.1006/jmbi.1997.1586
  • Primary Citation of Related Structures:  
    1KFS, 1KRP, 1KSP

  • PubMed Abstract: 
  • A two-metal-ion catalytic mechanism has previously been proposed for several phosphoryl-transfer enzymes. In order to extend the structural basis of this mechanism, crystal structures of three single-stranded DNA substrates bound to the 3'-5' exonucleoly ...

    A two-metal-ion catalytic mechanism has previously been proposed for several phosphoryl-transfer enzymes. In order to extend the structural basis of this mechanism, crystal structures of three single-stranded DNA substrates bound to the 3'-5' exonucleolytic active site of the large fragment of DNA polymerase I from Escherichia coli have been elucidated. The first is a 2.1 A resolution structure of a Michaelis complex between the large fragment (or Klenow fragment, KF) and a single-stranded DNA substrate, stabilized by low pH and flash-freezing. The positions and identities of the catalytic metal ions, a Zn2+ at site A and a Mg2+ at site B, have been clearly established. The structural and kinetic consequences of sulfur substitutions in the scissile phosphate have been explored. A complex with the Rp isomer of phosphorothioate DNA, refined at 2.2 A resolution, shows Zn2+ bound to both metal sites and a mispositioning of the substrate and attacking nucleophile. The complex with the Sp phosphorothioate at 2. 3 A resolution reveals that metal ions do not bind in the active site, having been displaced by a bulky sulfur atom. Steady-state kinetic experiments show that catalyzed hydrolysis of the Rp isomer was reduced only about 15-fold, while no enzyme activity could be detected with the Sp phosphorothioate, consistent with the structural observations. Furthermore, Mn2+ could not rescue the activity of the exonuclease on the Sp phosphorothioate. Taken together, these studies confirm and extend the proposed two-metal-ion exonuclease mechanism and provide a structural context to explain the effects of sulfur substitutions on this and other phosphoryl-transfer enzymes. These experiments also suggest that the possibility of metal-ion exclusion be taken into account when interpreting the results of Mn2+ rescue experiments.


    Related Citations: 
    • Structural Basis for the 3'-5' Exonuclease Activity of Escherichia Coli DNA Polymerase I: A Two Metal Ion Mechanism
      Beese, L.S., Steitz, T.A.
      (1991) EMBO J 10: 25

    Organizational Affiliation

    Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.



Macromolecules

Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
PROTEIN (DNA POLYMERASE I KLENOW FRAGMENT (E.C.2.7.7.7)) A605Escherichia coliMutation(s): 1 
EC: 2.7.7.7
Find proteins for P00582 (Escherichia coli (strain K12))
Explore P00582 
Go to UniProtKB:  P00582
Protein Feature View
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  • Reference Sequence
  • Find similar nucleic acids by:  Sequence   |   Structure
  • Entity ID: 1
    MoleculeChainsLengthOrganismImage
    DNA (5'-D(P*TP*TP*PST)-3')B3N/A
    Experimental Data & Validation

    Experimental Data

    • Method: X-RAY DIFFRACTION
    • Resolution: 2.20 Å
    • R-Value Free: 0.255 
    • R-Value Work: 0.190 
    • Space Group: P 43
    Unit Cell:
    Length ( Å )Angle ( ˚ )
    a = 101.6α = 90
    b = 101.6β = 90
    c = 85.2γ = 90
    Software Package:
    Software NamePurpose
    X-PLORmodel building
    X-PLORrefinement
    DENZOdata reduction
    SCALEPACKdata scaling
    X-PLORphasing

    Structure Validation

    View Full Validation Report



    Entry History 

    Deposition Data

    Revision History 

    • Version 1.0: 1998-02-25
      Type: Initial release
    • Version 1.1: 2008-05-22
      Changes: Version format compliance
    • Version 1.2: 2011-07-13
      Changes: Version format compliance