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  • The EMBO Journal (1999) 18, 6599 - 6609
  • doi:10.1093/emboj/18.23.6599

Crystal structure of a thwarted mismatch glycosylase DNA repair complex

Tracey E. Barrett1,2, Orlando D. Schärer3,4, Renos Savva1,5, Tom Brown6, Josef Jiricny7, Gregory L. Verdine3 and Laurence H. Pearl1,2,8

  1. Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
  2. Present address: Centre for Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
  3. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
  4. Present address: Department of Cell Biology and Genetics, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands
  5. Present address: Laboratory of Molecular Biology, Department of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK
  6. Department of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
  7. Institute for Medical Radiobiology, August Forel-Strasse 7, 8029 Zürich, Switzerland
  8. Joint UCL/LICR Crystallography Laboratory, University College London, Gower Street, London WC1E 6BT, UK

Correspondence to:

Laurence H. Pearl, E-mail: l.pearl@biochem.ucl.ac.uk

Received 21 July 1999; Accepted 6 October 1999; Revised 6 October 1999

The bacterial mismatch-specific uracil-DNA glycosylase (MUG) and eukaryotic thymine-DNA glycosylase (TDG) enzymes form a homologous family of DNA glycosylases that initiate base-excision repair of G:U/T mismatches. Despite low sequence homology, the MUG/TDG enzymes are structurally related to the uracil-DNA glycosylase enzymes, but have a very different mechanism for substrate recognition. We have now determined the crystal structure of the Escherichia coli MUG enzyme complexed with an oligonucleotide containing a non-hydrolysable deoxyuridine analogue mismatched with guanine, providing the first structure of an intact substrate-nucleotide productively bound to a hydrolytic DNA glycosylase. The structure of this complex explains the preference for G:U over G:T mispairs, and reveals an essentially non-specific pyrimidine-binding pocket that allows MUG/TDG enzymes to excise the alkylated base, 3,N4-ethenocytosine. Together with structures for the free enzyme and for an abasic-DNA product complex, the MUG–substrate analogue complex reveals the conformational changes accompanying the catalytic cycle of substrate binding, base excision and product release.

  • Keywords:

    • DNA repair,
    • mismatch DNA glycosylase,
    • structure