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- Title
Evolution of a phage RuvC endonuclease for resolution of both Holliday and branched DNA junctions.
- Authors
Curtis, Fiona A.; Reed, Patricia; Sharples, Gary J.
- Abstract
Resolution of Holliday junction recombination intermediates in most Gram-negative bacteria is accomplished by the RuvC endonuclease acting in concert with the RuvAB branch migration machinery. Gram-positive species, however, lack RuvC, with the exception of distantly related orthologues from bacteriophages infecting Lactococci and Streptococci. We have purified one of these proteins, 67RuvC, fromLactococcus lactisphage bIL67 and demonstrated that it functions as a Holliday structure resolvase. Differences in the sequence selectivity of resolution between 67RuvC andEscherichia coliRuvC were noted, although both enzymes prefer to cleave 3′ of thymidine residues. However, unlike its cellular counterpart, 67RuvC readily binds and cleaves a variety of branched DNA substrates in addition to Holliday junctions. Plasmids expressing 67RuvC induce chromosomal breaks, probably as a consequence of replication fork cleavage, and cannot be recovered from recombination-defectiveE. colistrains. Despite these deleterious effects, 67RuvC constructs suppress the UV light sensitivity ofruvA,ruvABandruvABCmutant strains confirming that the phage protein mediates Holliday junction resolutionin vivo. The characterization of 67RuvC offers a unique insight into how a Holliday junction-specific resolvase can evolve into a debranching endonuclease tailored to the requirements of phage recombination.
- Subjects
GRAM-negative bacteria; BACTERIA; ENDONUCLEASES; NUCLEASES; LACTOCOCCUS; STREPTOCOCCACEAE; STREPTOCOCCUS; ESCHERICHIA coli
- Publication
Molecular Microbiology, 2005, Vol 55, Issue 5, p1332
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1111/j.1365-2958.2004.04476.x