Crystal Structure of Human uracil-DNA Glycosylase in Complex With a Protein Inhibitor: Protein Mimicry of DNA

Cell. 1995 Sep 8;82(5):701-8. doi: 10.1016/0092-8674(95)90467-0.


Uracil-DNA glycosylase inhibitor (Ugi) is a B. subtilis bacteriophage protein that protects the uracil-containing phage DNA by irreversibly inhibiting the key DNA repair enzyme uracil-DNA glycosylase (UDG). The 1.9 A crystal structure of Ugi complexed to human UDG reveals that the Ugi structure, consisting of a twisted five-stranded antiparallel beta sheet and two alpha helices, binds by inserting a beta strand into the conserved DNA-binding groove of the enzyme without contacting the uracil specificity pocket. The resulting interface, which buries over 1200 A2 on Ugi and involves the entire beta sheet and an alpha helix, is polar and contains 22 water molecules. Ugi binds the sequence-conserved DNA-binding groove of UDG via shape and electrostatic complementarity, specific charged hydrogen bonds, and hydrophobic packing enveloping Leu-272 from a protruding UDG loop. The apparent mimicry by Ugi of DNA interactions with UDG provides both a structural mechanism for UDG binding to DNA, including the enzyme-assisted expulsion of uracil from the DNA helix, and a crystallographic basis for the design of inhibitors with scientific and therapeutic applications.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites / genetics
  • Crystallography
  • DNA / metabolism
  • DNA Glycosylases*
  • DNA Repair / physiology*
  • DNA-Binding Proteins / metabolism
  • Humans
  • Image Processing, Computer-Assisted
  • N-Glycosyl Hydrolases / antagonists & inhibitors
  • N-Glycosyl Hydrolases / chemistry*
  • N-Glycosyl Hydrolases / ultrastructure
  • Protein Binding / physiology
  • Protein Conformation
  • Uracil / metabolism
  • Uracil-DNA Glycosidase
  • Viral Proteins / metabolism*
  • Viral Proteins / ultrastructure


  • DNA-Binding Proteins
  • Viral Proteins
  • uracil-DNA glycosylase inhibitor protein, B. subtilis bacteriophage
  • Uracil
  • DNA
  • DNA Glycosylases
  • N-Glycosyl Hydrolases
  • Uracil-DNA Glycosidase