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Journal of Bacteriology, February 2000, p. 607-612, Vol. 182, No. 3
Department of Biology and Rosenstiel Basic
Medical Sciences Research Center, Brandeis University, Waltham,
Massachusetts 02454-9110
Received 7 September 1999/Accepted 5 November 1999
The RecJ protein of Escherichia coli plays an important
role in a number of DNA repair and recombination pathways. RecJ
catalyzes processive degradation of single-stranded DNA in a 5'-to-3'
direction. Sequences highly related to those encoding RecJ can be found
in most of the eubacterial genomes sequenced to date. From alignment of
these sequences, seven conserved motifs are apparent. At least five of
these motifs are shared among a large family of proteins in eubacteria,
eukaryotes, and archaea, including the PPX1 polyphosphatase of yeast
and Drosophila Prune. Archaeal genomes are particularly rich in such sequences, but it has not been clear whether any of the
encoded proteins play a functional role similar to that of RecJ
exonuclease. We have investigated three such proteins from
Methanococcus jannaschii with the strongest overall
sequence similarity to E. coli RecJ. Two of the genes,
MJ0977 and MJ0831, partially complement a recJ mutant
phenotype in E. coli. The expression of MJ0977 in E. coli resulted in high levels of a thermostable single-stranded
DNase activity with properties similar to those of RecJ exonuclease.
Despite overall weak sequence similarity between the MJ0977 product and
RecJ, these nucleases are likely to have similar biological functions.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
A Thermostable Single-Strand DNase from
Methanococcus jannaschii Related to the RecJ Recombination
and Repair Exonuclease from Escherichia coli
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Corresponding author. Mailing address: Rosenstiel Basic
Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110. Phone: (781) 736-2487. Fax: (781) 736-2405. E-mail: lovett{at}hydra.rose.brandeis.edu.
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