A CHEA CHEW OPERON IN BORRELIA-BURGDORFERI, THE AGENT OF LYME-DISEASE

Borrelia burgdorferi sensu stricto homologues of cheA and cheW were cl oned and characterized. A combination of strategies such as polymerase chain reaction (PCR) using degenerate primers, random-primed gene wal king PCR and construction of a lambda library were used to identify th e putative cheA gene. Sequence analysis of the DNA fragments obtained from the CT strain identified a 2,592-bp open reading frame (ORF) enco ding an 864-amino-acid protein with significant similarity (53-64.6% i dentical residues) to the CheA of several genera of eubacteria. In par ticular, hallmarks of a histidine kinase family were found such as the location of the histidine autophosphorylation domain very close to th e NH, terminus and the nucleotide-binding site. A second ORF located i mmediately downstream from the putative borrelial cheA gene encoded a 195-amino-acid protein which displayed a high level of similarity to b acterial CheW. Using reverse transcription PCR, we demonstrated that c heA and cheW form an operon with an upstream, unidentified ORF. The ch eA and cheW homologues were located at 722-737 kbp, 738-768 kbp and 74 3-824 kbp on the linear chromosomes of B. borgdorferi sensu stricto, B . garinii and B. afzelii, respectively. Identification of cheA and che W is the first step toward elucidation of a possible role of chemotaxi s in virulence of the Lyme disease borreliae.