Identification and purification of a single-stranded-DNA-specific exonuclease encoded by the recJ gene of Escherichia coli.
The Escherichia coli recJ gene product was overproduced using a plasmid that carries the recJ gene downstream of a strong regulatable promoter and a strong ribosome-binding site. Overexpression of recJ produced a concomitant increase in the levels of single-stranded-DNA-specific nuclease activity present in crude cell extracts. This nuclease activity was purified to homogeneity and found to reside in a 60-kDa polypeptide. This polypeptide was induced with recJ overexpression and had the size and N-terminal amino acid sequence identical to the predicted RecJ protein sequence. The RecJ nuclease degraded linear single-stranded DNA but did not have exonuclease activity on linear double-stranded substrates or endonuclease activity on either single-stranded or double-stranded substrates. The RecJ exonuclease had greater activity on duplex DNA molecules with 5'-rather than 3'-single-stranded tails.
Lovett
S T
ST
Department of Cell and Molecular Biology, Dana-Farber Cancer Institute, Boston, MA 02115.
Kolodner
R D
RD
D000595:Amino Acid Sequence; D001483:Base Sequence; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000302:isolation & purification*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D011995:Recombination, Genetic; D013379:Substrate Specificity
D004277:DNA, Single-Stranded; D005090:Exodeoxyribonucleases