I. Uchida et al., CLONING AND CHARACTERIZATION OF A GENE WHOSE PRODUCT IS A TRANSACTIVATOR OF ANTHRAX TOXIN SYNTHESIS, Journal of bacteriology, 175(17), 1993, pp. 5329-5338
The 184-kb Bacillus anthracis plasmid pXO1, which is required for viru
lence, contains three genes encoding the protein components of anthrax
toxin, cya (edema factor gene), lef (lethal factor gene), and pag (pr
otective antigen gene). Expression of the three proteins is induced by
bicarbonate or serum. Using a pag-lacZ transcriptional construct to m
easure pag promoter activity, we cloned in Bacillus subtilis a gene (a
txA) whose product acts in trans to stimulate anthrax toxin expression
. Deletion analysis located atxA on a 2.0-kb fragment between cya and
pag. DNA sequencing identified one open reading frame encoding 476 ami
no acids with a predicted M(r) of 55,673, in good agreement with the v
alue of 53 kDa obtained by in vitro transcription-translation analysis
. The cloned atxA gene complemented previously characterized Tn917 ins
ertion mutants UM23 tp29 and UM23 tp32 (J. M. Hornung and C. B. Thorne
, Abstr. 91st Gen. Meet. Am. Soc. Microbiol. 1991, abstr. D-121, p. 98
), which are deficient in synthesis of all three toxin proteins. These
results demonstrate that the atxA product activates not only transcri
ption of pag but also that of cya and lef. Beta-Galactosidase synthesi
s from the pag-lacZ transcriptional fusion construct introduced into a
n insertion mutant (UM23 tp62) which does not require bicarbonate for
toxin synthesis indicated that additional regulatory genes other than
atxA play a role in the induction of anthrax toxin gene expression by
bicarbonate.