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J. Bacteriol., 01 1996, 130-135, Vol 178, No. 1
JD Carroll, MJ Daly and KW Minton
Deinococcus (formerly Micrococcus) radiodurans is remarkable for its
extraordinary resistance to ionizing and UV irradiation and many other
agents that damage DNA. This organism can repair > 100 double-strand
breaks per chromosome induced by ionizing radiation without lethality or
mutagenesis. We have previously observed that expression of D. radiodurans
recA in Escherichia coli appears lethal. We now find that the RecA protein
of D. radiodurans is ot detectable in D. radiodurans except in the setting
of DNA damage and that termination of its synthesis is associated with the
onset of deinococcal growth. The synthesis of Shigella flexneri RecA
(protein sequence identical to that of E. coli RecA) in recA-defective D.
radiodurans is described. Despite a large accumulation of the S. flexneri
RecA in D. radiodurans, there is no complementation of any D. radiodurans
recA phenotype, including DNA damage sensitivity, inhibition of natural
transformation, or inability to support a plasmid that requires RecA for
replication. To ensure that the cloned S. flexneri recA gene was not
inactivated, it was rescued from D. radiodurans and was shown to function
normally in E. coli. We conclude that neither D. radiodurans nor S.
flexneri RecA is functional in the other species, nor are the kinetics of
induction and suppression similar to each other, indicating a difference
between these two proteins in their modes of action.
Copyright © 1996, American Society for Microbiology
Expression of recA in Deinococcus radiodurans
Department of Pathology, F. E. Hebert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814- 4799, USA.
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