Structure of Hjc, a Holliday junction resolvase, from Sulfolobus solfataricus

Proc Natl Acad Sci U S A. 2001 May 8;98(10):5509-14. doi: 10.1073/pnas.091613398. Epub 2001 May 1.


The 2.15-A structure of Hjc, a Holliday junction-resolving enzyme from the archaeon Sulfolobus solfataricus, reveals extensive structural homology with a superfamily of nucleases that includes type II restriction enzymes. Hjc is a dimer with a large DNA-binding surface consisting of numerous basic residues surrounding the metal-binding residues of the active sites. Residues critical for catalysis, identified on the basis of sequence comparisons and site-directed mutagenesis studies, are clustered to produce two active sites in the dimer, about 29 A apart, consistent with the requirement for the introduction of paired nicks in opposing strands of the four-way DNA junction substrate. Hjc displays similarity to the restriction endonucleases in the way its specific DNA-cutting pattern is determined but uses a different arrangement of nuclease subunits. Further structural similarity to a broad group of metal/phosphate-binding proteins, including conservation of active-site location, is observed. A high degree of conservation of surface electrostatic character is observed between Hjc and T4-phage endonuclease VII despite a complete lack of structural homology. A model of the Hjc-Holliday junction complex is proposed, based on the available functional and structural data.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Catalytic Domain
  • Dimerization
  • Endodeoxyribonucleases / chemistry*
  • Holliday Junction Resolvases
  • Models, Molecular
  • Molecular Sequence Data
  • Sulfolobus / enzymology*


  • Endodeoxyribonucleases
  • Holliday Junction Resolvases

Associated data

  • PDB/1HH1