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Crystal Structure of T7 Endo I resolvase in complex with a Holliday Junction
Structural highlights
FunctionENDO_BPT7 Junction-resolving enzyme that selectively binds and cleaves four-way (Holliday) DNA junctions present after viral genomic replication. These intermediates are created during DNA repair, processing of stalled replication forks and homologous genetic recombination. Introduces two nicks on the two non-crossing strands, at 5' sides of the junction. Participates also together with gp6 in the degradation of host chromosome to provide nucleotides for phage DNA synthesis.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe four-way (Holliday) DNA junction is the central intermediate in homologous recombination, a ubiquitous process that is important in DNA repair and generation of genetic diversity. The penultimate stage of recombination requires resolution of the DNA junction into nicked-duplex species by the action of a junction-resolving enzyme, examples of which have been identified in a wide variety of organisms. These enzymes are nucleases that are highly selective for the structure of branched DNA. The mechanism of this selectivity has, however, been unclear in the absence of structural data. Here we present the crystal structure of the junction-resolving enzyme phage T7 endonuclease I in complex with a synthetic four-way DNA junction. Although the enzyme is structure-selective, significant induced fit occurs in the interaction, with changes in the structure of both the protein and the junction. The dimeric enzyme presents two binding channels that contact the backbones of the junction's helical arms over seven nucleotides. These interactions effectively measure the relative orientations and positions of the arms of the junction, thereby ensuring that binding is selective for branched DNA that can achieve this geometry. The structural basis of Holliday junction resolution by T7 endonuclease I.,Hadden JM, Declais AC, Carr SB, Lilley DM, Phillips SE Nature. 2007 Oct 4;449(7162):621-4. Epub 2007 Sep 16. PMID:17873858[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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