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J Bacteriol, July 1998, p. 3522-3528, Vol. 180, No. 14
Department of Bacteriology, National
Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo
162, Japan
Received 15 January 1998/Accepted 9 May 1998
virF is the master regulator which activates the
virulence determinant genes of Shigella spp. such as
ipaBCD and virG. We previously reported that
expression of virF itself is regulated in a pH-dependent
manner and that cpxA, a sensor of a two-component regulatory system, is involved in this regulation (S. Nakayama and
H. Watanabe, J. Bacteriol. 177:5062-5069, 1995). Disruption of cpxR, which has been thought to be the cognate response
regulator of cpxA (J. Dong, S. Iuchi, H.-S. Kwan, Z. Lue, and E. C. C. Lin, Gene 136:227-230, 1993), abolished
virF expression almost completely. Purified CpxR
bound directly to the upstream region of virF. Binding capacity was enhanced when CpxR was phosphorylated by coincubation with acetyl phosphate in vitro. Furthermore, we observed that phosphorylated CpxR could activate virF transcription in
vitro. These results clearly indicated that CpxR was an
essential activator for virF expression and strongly
suggested that the binding of phosphorylated CpxR to the target
site upstream of the virF gene induced a direct activation
of virF transcription.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of cpxR as a Positive
Regulator Essential for Expression of the Shigella sonnei
virF Gene
*
Corresponding author. Mailing address: Department of
Bacteriology, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162, Japan. Phone: (81-3) 5285-1111, ext. 2201. Fax:
(81-3) 5285-1163. E-mail: haruwata{at}nih.go.jp.
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