Unique genetic arrangement in the dnaA region of the Borrelia burgdorferi linear chromosome: nucleotide sequence of the dnaA gene

Abstract

The complete nucleotide sequence of the Borrelia burgdorferi dnaA gene (encoding the initiator protein of chromosome replication) and its flanking regions was determined. The putative DnaA polypeptide exhibited 29-42% identity with those of other eubacteria. The gene order in the dnaA region at the centre of the B. burgdorferi linear chromosome is rnpA-rpmH-dnaN-dnaA-gyrB-gyrA in contrast to the consensus eubacterial order of rnpA-rpmH-dnaA-dnaN-recF-gyrB, suggesting a rearrangement during the evolution of the Borrelia chromosome. We did not detect the multiple 9-nucleotide repeats known as DnaA boxes, which characterise origin of replications, in the dnaA-gyrB and dnaA-dnaN intergenic regions. In addition B. burgdorferi DnaA protein differs considerably from those of other eubacteria in a normally highly conserved region at the C-terminus of the polypeptide which may be involved in DNA binding.