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

Charles S. Bond, Mamuka Kvaratskhelia, Derek Richard, Malcolm F. White, William N. Hunter

Research output: Contribution to journalArticlepeer-review

72 Citations (Scopus)


The 2.15-Å 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 Å 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.

Original languageEnglish
Pages (from-to)5509-5514
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number10
Publication statusPublished - 2001
Externally publishedYes


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