1EJ9

CRYSTAL STRUCTURE OF HUMAN TOPOISOMERASE I DNA COMPLEX


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.281 
  • R-Value Work: 0.214 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Novel insights into catalytic mechanism from a crystal structure of human topoisomerase I in complex with DNA.

Redinbo, M.R.Champoux, J.J.Hol, W.G.

(2000) Biochemistry 39: 6832-6840


  • PubMed Abstract: 
  • Human topoisomerase I helps to control the level of DNA supercoiling in cells and is vital for numerous DNA metabolic events, including replication, transcription, and recombination. The 2.6 A crystal structure of human topoisomerase I in noncovalent ...

    Human topoisomerase I helps to control the level of DNA supercoiling in cells and is vital for numerous DNA metabolic events, including replication, transcription, and recombination. The 2.6 A crystal structure of human topoisomerase I in noncovalent complex with a DNA duplex containing a cytosine at the -1 position of the scissile strand rather than the favored thymine is reported. The hydrogen bond between the O2 position of this -1 base and the epsilon-amino of the conserved Lys-532 residue, the only base-specific contact observed previously in the human topoisomerase I-DNA interaction, is maintained in this complex. Several unique features of this structure, however, have implications for the DNA-binding and active-site mechanisms of the enzyme. First, the ends of the DNA duplex were observed to shift by up to 5.4 A perpendicular to the DNA helical axis relative to structures reported previously, suggesting a novel degree of plasticity in the interaction between human topoisomerase I and its DNA substrate. Second, 12 additional residues at the NH(2) terminus of the protein (Trp-203-Gly-214) could be built in this structure, and they were found to pack against the putative hinge region implicated in the clamping of the enzyme around duplex DNA. Third, a water molecule was observed adjacent to the scissile phosphate and the active-site residues; the potential specific base character of this solvent molecule in the active-site mechanism of the enzyme is discussed. Fourth, the scissile phosphate group was found to be rotated by 75 degrees, bringing Lys-532 into hydrogen-bonding distance of one of the nonbridging phosphate oxygens. This orientation of the scissile phosphate group implicates Lys-532 as a fifth active-site residue, and also mimics the orientation observed for the 3'-phosphotyrosine linkage in the covalent human topoisomerase I-DNA complex structure. The implications of these structural features for the mechanism of the enzyme are discussed, including the potential requirement for a rotation of the scissile phosphate group during DNA strand cleavage and covalent attachment.


    Organizational Affiliation

    Department of Biological Structure and Biomolecular Structure Center, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, Washington 98195, USA. redinbo@unc.edu




Macromolecules

Find similar proteins by: Sequence  |  Structure


Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
DNA TOPOISOMERASE I
A
563Homo sapiensGene Names: TOP1
EC: 5.99.1.2
Find proteins for P11387 (Homo sapiens)
Go to Gene View: TOP1
Go to UniProtKB:  P11387
Entity ID: 1
MoleculeChainsLengthOrganism
DNA (5'-D(*C*AP*AP*AP*AP*AP*GP*AP*CP*TP*CP*AP*GP*AP*AP*AP*AP*AP*TP*TP*TP*TP*T)-3')C23N/A
Entity ID: 2
MoleculeChainsLengthOrganism
DNA (5'-D(*C*AP*AP*AP*AP*AP*TP*TP*TP*TP*TP*CP*TP*GP*AP*GP*TP*CP*TP*TP*TP*TP*T)-3')D23N/A
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.281 
  • R-Value Work: 0.214 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 56.980α = 90.00
b = 124.920β = 93.84
c = 72.290γ = 90.00
Software Package:
Software NamePurpose
DENZOdata reduction
AMoREphasing
SCALEPACKdata scaling
X-PLORrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2000-08-03
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance