Nucleic Acids Research, Vol 27, Issue 5 1275-1282, Copyright © 1999 by Oxford University Press
C Mezard, H George, AA Davies, AJ van Gool, D Zerbib, A Stasiak and SC West
The RuvABC proteins of Escherichia coli process recombination intermediates
during genetic recombination and DNA repair. RuvA and RuvB promote branch
migration of Holliday junctions, a process that extends heteroduplex DNA.
Together with RuvC, they form a RuvABC complex capable of Holliday junction
resolution. Branch migration by RuvAB is mediated by RuvB, a hexameric ring
protein that acts as an ATP- driven molecular pump. To gain insight into
the mechanism of branch migration, random mutations were introduced into
the ruvB gene by PCR and a collection of mutant alleles were obtained.
Mutation of leucine 268 to serine resulted in a severe UV-sensitive
phenotype, characteristic of a ruv defect. Here, we report a biochemical
analysis of the mutant protein RuvBL268S. Unexpectedly, the purified
protein is fully active in vitro with regard to its ATPase, DNA binding and
DNA unwinding activities. It also promotes efficient branch migration in
combination with RuvA, and forms functional RuvABC-Holliday junction
resolvase complexes. These results indicate that RuvB may perform some
additional, and as yet undefined, function that is necessary for cell
survival after UV-irradiation.
ARTICLES
Escherichia coli RuvBL268S: a mutant RuvB protein that exhibits wild- type activities in vitro but confers a UV-sensitive ruv phenotype in vivo
Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, UK.
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