HOMOLOGS OF HELICASE GENES PRIA AND RUVAB OF BORRELIA-BURGDORFERI, THE LYME BORRELIOSIS AGENT

A DNA library of strain HB19 from Borrelia burgdorferi sensu stricto, an agent of Lyme borreliosis, was constructed in the cosmid pLA2917. G enes involved in initiation of DNA replication and resolution of recom bination intermediates (Holliday junctions) were found on a 23-kbp reg ion up to 0.7 kbp of the ''left'' extremity of the linear chromosome i n representative species of B. burgdorferi sensu late. The potential r uvB 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 comp rises the homologues of ruvA, queA and pfbB. Expression of the B. burg dorferi ruvB and ruvA genes renders a wild-type Escherichia coli sensi tive to UV light and mitomycin, indicative of negative complementation . priA, which encodes the potential recognition factor for the primoso me assembly site, was found at 15 kbp from the left telomere. RuvB and PriA sequences have motifs characteristic of helicases: a DExH box an d an ATP binding site.