Chi sites are octameric nucleotide sequences in DNA that stimulate the Rec-BCD pathway of homologous recombination in Escherichia coli. Stimulation is maximal at the Chi site, decreases approximately a factor of two for each 2–3 kb to one side, but is insignificant to the other side of Chi. Chi stimulates recombination by interaction with RecBCD enzyme, which has multiple enzymatic activities and multiple physiological roles in recombination, repair, and replication. Chi appears to be active throughout the enteric bacteria; other nucleotide sequences may similarly interact with RecBCD-like enzymes in other bacteria. This chapter reviews the properties of Chi, its interaction with RecBCD enzyme, and its occurrence on the chromosome of E. coli and other organisms.
KeywordsHomologous Recombination Nuclease Activity Bacteriophage Lambda RecA Protein Homologous Pairing
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