1R49

Human topoisomerase I (Topo70) double mutant K532R/Y723F


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.13 Å
  • R-Value Free: 0.339 
  • R-Value Work: 0.277 
  • R-Value Observed: 0.280 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

The role of lysine 532 in the catalytic mechanism of human topoisomerase I.

Interthal, H.Quigley, P.M.Hol, W.G.Champoux, J.J.

(2004) J Biol Chem 279: 2984-2992

  • DOI: 10.1074/jbc.M309959200
  • Primary Citation of Related Structures:  
    1R49

  • PubMed Abstract: 
  • Based on co-crystal structures of human topoisomerase I with bound DNA, Lys(532) makes a minor groove contact with the strongly preferred thymidine residue at the site of covalent attachment (-1 position). Replacement of Lys(532) with either arginine or alanine has essentially no effect on the sequence preference of the enzyme, indicating that this interaction is not required for the preference for a T at the -1 position ...

    Based on co-crystal structures of human topoisomerase I with bound DNA, Lys(532) makes a minor groove contact with the strongly preferred thymidine residue at the site of covalent attachment (-1 position). Replacement of Lys(532) with either arginine or alanine has essentially no effect on the sequence preference of the enzyme, indicating that this interaction is not required for the preference for a T at the -1 position. Although both the cleavage and religation activities of the K532R mutant enzyme are reduced, cleavage is reduced to a greater extent than religation. The reverse is true for the K532A mutant enzyme with religation so impaired that the nicked intermediate accumulates during plasmid relaxation assays. Consistent with the shift in the cleavage religation equilibrium toward cleavage for the K532A mutant enzyme, expression of the mutant enzyme in Saccharomyces cerevisiae is cytotoxic, and thus this mutant enzyme mimics the effects of the anticancer drug camptothecin. Cleavage assays with the mutant enzymes using an oligonucleotide containing a 5'-bridging phosphorothiolate indicate that Lys(532) functions as a general acid during cleavage to protonate the leaving 5'-oxygen. It is possible that the contact with the -1 base is important during catalysis to provide positional rigidity to the active site. The corresponding residues in the vaccinia virus topoisomerase and the tyrosine recombinases may have similar critical roles in catalysis.


    Organizational Affiliation

    Department of Microbiology, University of Washington School of Medicine, Seattle, Washington 98195-7242, USA.



Macromolecules

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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
DNA topoisomerase IC [auth A]592Homo sapiensMutation(s): 2 
Gene Names: TOP1
EC: 5.99.1.2 (PDB Primary Data), 5.6.2.1 (UniProt)
Find proteins for P11387 (Homo sapiens)
Explore P11387 
Go to UniProtKB:  P11387
NIH Common Fund Data Resources
PHAROS:  P11387
Protein Feature View
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  • Reference Sequence
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Entity ID: 1
MoleculeChainsLengthOrganismImage
5'-D(*AP*AP*AP*AP*AP*GP*AP*CP*TP*TP*AP*GP*AP*AP*AP*AP*AP*TP*TP*TP*TP*T)-3'A [auth B]22N/A
Protein Feature View
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsLengthOrganismImage
5'-D(P*AP*AP*AP*AP*AP*TP*TP*TP*TP*TP*CP*TP*AP*AP*GP*TP*CP*TP*TP*TP*TP*T)-3'B [auth C]22N/A
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.13 Å
  • R-Value Free: 0.339 
  • R-Value Work: 0.277 
  • R-Value Observed: 0.280 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 56.944α = 90
b = 118.638β = 98.33
c = 71.651γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
HKL-2000data reduction
SCALEPACKdata scaling
AMoREphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-12-16
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance