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J. Biol. Chem., Vol. 276, Issue 49, 46004-46010, December 7, 2001
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From the Department of Chemistry and Biochemistry, University of
Maryland, College Park, Maryland 20742
The RecB subunit of the Escherichia
coli RecBCD enzyme has both helicase and nuclease activities. The
helicase function was localized to an N-terminal domain, whereas the
nuclease activity was found in a C-terminal domain. Recent analysis has
uncovered a group of proteins that have weak amino acid sequence
similarity to the RecB nuclease domain and that are proposed to
constitute a family of related proteins (Aravind, L., Walker, D. R., and Koonin, E. V. (1999) Nucleic Acids Res. 27, 1223-1242). One is the E. coli RecE protein (exonuclease
VIII), an ATP-independent exonuclease that degrades the 5'-terminated
strand of double-stranded DNA. We have made mutations in several
residues of RecE that align with the critical residues of RecB, and we
find that the mutations reduce or abolish the nuclease activity of RecE
but do not affect the enzyme binding to linear double-stranded DNA.
Proteolysis experiments with subtilisin show that a stable
34-kilodalton C-terminal domain that contains these critical residues
has nuclease activity, whereas no stable proteolytic fragments
accumulate from the N-terminal portion of RecE. These results show that
RecE has a nuclease domain and active site that are similar to RecB,
despite the very weak sequence similarity between the two proteins.
These similarities support the hypothesis that the nuclease domains of
the two proteins are evolutionarily related.
Structure and Function of the Escherichia coli RecE
Protein, a Member of the RecB Nuclease Domain Family*
*
This work was supported by Grant GM39777 from the National
Institutes of Health.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed. Tel.: 301-405-1821;
Fax: 301-314-9121; E-mail: dj13@umail.umd.edu.
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