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.