RecBCD enzyme is altered upon cutting DNA at a chi recombination hotspot.
During its unidirectional unwinding of DNA, RecBCD enzyme cuts one DNA strand near a properly oriented Chi site, a hotspot of homologous genetic recombination in Escherichia coli. We report here that individual DNA molecules containing two properly oriented Chi sites were cut with about 40% efficiency at one or the other Chi site but not detectably at both Chi sites. Furthermore, initial incubation of RecBCD with Chi-containing DNA reduced its ability both to unwind DNA and to cut at Chi sites on subsequently added DNA molecules much more than did initial incubation with Chi-free DNA; the nuclease activity was less severely affected. These results imply that RecBCD loses its Chi-cutting activity upon cutting at a single Chi site and provide a mechanism for ensuring single genetic exchanges near the ends of DNA molecules.
Taylor
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AF
Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
Smith
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GR
D010582:Bacteriophage lambda / Q000235:genetics; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D007700:Kinetics; D010957:Plasmids; D011995:Recombination, Genetic; D013379:Substrate Specificity
D004269:DNA, Bacterial; D004279:DNA, Viral; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V