SEQUENCE-ANALYSIS OF THE RICKETTSIA-PROWAZEKII GYR-A GENE

The Rickettsia prowazekii (Rp) gyrA gene, which codes for a subunit of DNA gyrase in this obligate intracellular bacterium, has been isolate d and characterized. Nucleotide sequence analysis revealed an open rea ding frame (ORF), initiating with a GTG start codon, of 2718 bp that c ould encode a protein of 905 amino acids (aa) with a calculated M(r) o f 101 048. The Rp gyrase subunit A (GyrA), when compared to GyrA analo gs of other bacterial species, exhibited 43 to 50% identity. Alignment of the Rp GyrA aa sequence with the other analogs revealed the presen ce of a span of additional aa within the putative DNA-binding domain. The lack of an ORF within 865 bp upstream from the Rp gyrA demonstrate s a Rp gene organization different from that of characterized gyrA fro m other species. Despite the similarity to Escherichia coli GyrA, Rp G yrA did not complement an E. coli gyrA temperature-sensitive mutant. H owever, Rp gyrA was dominant to an E. coli gyrA96 nalidixic-acid-resis tant (Nal(R)) mutant, conferring Nal sensitivity when introduced into the Nal(R) E. Coli Strain.