title: The 30-kDa C-terminal domain of the RecB protein is critical for the nuclease activity, but not the helicase activity, of the RecBCD enzyme from Escherichia coli.
abstract: The RecBCD enzyme from Escherichia coli is an ATP-dependent helicase and an ATP-stimulated nuclease. The 3' --> 5' exonuclease activity on double-stranded DNA is suppressed when the enzyme encounters a recombinational hot spot, called chi (chi). We have prepared a RecB deletion mutant (RecB1-929) by using results of limited proteolysis experiments that indicated that the RecB subunit consists of two main domains. The RecB1-929 protein, comprising the 100-kDa N-terminal domain of RecB, is an ATP-dependent helicase and a single-stranded DNA-dependent ATPase. Reconstitution of RecB1-929 with RecC and RecD leads to processive unwinding of a linearized plasmid. However, the reconstituted RecB1-929CD enzyme has lost the single-strand endo- and exonuclease and the double-strand exonuclease activities of the RecBCD enzyme. These results show that the 30-kDa C-terminal domain of RecB has an important role in the nuclease activity of RecBCD. On the basis of these findings, we propose the RecB C-terminal domain swing model to explain RecBCD's transformation from a 3' --> 5' exonuclease to a helicase when it meets a chi site.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
authors.forename: M
authors.initials: M
authors.lastname: Yu
authors.forename: J
authors.initials: J
authors.lastname: Souaya
authors.forename: D A
authors.initials: DA
authors.lastname: Julin
mesh_terms: D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; D004265:DNA Helicases