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A DNA library of strain HB19 from Borrelia burgdorferi sensu stricto, an agent of
Lyme borreliosis, was constructed in the cosmid pLA2917. Genes involved in initiation of DNA replication and resolution of recombination intermediates (Holliday junctions) were found on a 23-kbp region up to 0.7 kbp of the "left" extremity of the linear chromosome in representative species of B. burgdorferi sensu lato. The potential ruvB gene, located at 22 kbp from the left telomere, was identified by the similarity of its deduced amino acid sequence to RuvB (helicases) of other bacteria. B. burgdorferi ruvB is part of an operon which comprises the homologues of ruvA, queA and pfbB. Expression of the B. burgdorferi ruvB and ruvA genes renders a wild-type Escherichia coli sensitive to UV light and mitomycin, indicative of negative complementation. priA, which encodes the potential recognition factor for the primosome assembly site, was found at 15 kbp from the left telomere. RuvB and PriA sequences have motifs characteristic of helicases: a DExH box and an ATP binding site.