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RecBCD enzyme and the repair of double-stranded DNA breaks.

Authors
Type
Published Article
Journal
Microbiology and Molecular Biology Reviews
Publisher
American Society for Microbiology
Volume
72
Issue
4
Identifiers
DOI: 10.1128/MMBR.00020-08
Source
Kowalczykowski Lab
License
Unknown

Abstract

The RecBCD enzyme of Escherichia coli is a helicase-nuclease that initiates the repair of double-stranded DNA breaks by homologous recombination. It also degrades linear double-stranded DNA, protecting the bacteria from phages and extraneous chromosomal DNA. The RecBCD enzyme is, however, regulated by a cis-acting DNA sequence known as Chi (crossover hotspot instigator) that activates its recombination-promoting functions. Interaction with Chi causes an attenuation of the RecBCD enzyme s vigorous nuclease activity, switches the polarity of the attenuated nuclease activity to the 5 strand, changes the operation of its motor subunits, and instructs the enzyme to begin loading the RecA protein onto the resultant Chi-containing single-stranded DNA. This enzyme is a prototypical example of a molecular machine: the protein architecture incorporates several autonomous functional domains that interact with each other to produce a complex, sequence-regulated, DNA-processing machine. In this review, we discuss the biochemical mechanism of the RecBCD enzyme with particular emphasis on new developments relating to the enzyme s structure and DNA translocation mechanism.

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