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Journal of Bacteriology, August 1998, p. 3973-3977, Vol. 180, No. 15
Laboratory of Molecular Microbiology, School
of Agriculture, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
Received 30 March 1998/Accepted 29 May 1998
The two components ArcB and ArcA play a crucial role in the signal
transduction implicated in the complex transcriptional regulatory
network that allows Escherichia coli to sense various respiratory growth conditions. ArcB is a hybrid sensor kinase having
multiple phosphorylation sites in its primary amino acid sequence,
including a transmitter, a receiver, and a histidine-containing phosphotransfer (HPt) domain. ArcA is a DNA-binding transcriptional regulator with a receiver domain. Results of recent in vitro studies revealed multistep His-to-Asp phosphotransfer circuitry in the ArcB-ArcA signaling system. For this report we conducted a series of in
vivo experiments using a set of crucial ArcB mutants to evaluate the
regulation of the sdh operon. The results suggested that
the phosphorylated His-717 site in the HPt domain of ArcB is essential
for anaerobic repression of sdh. Nonetheless, the ArcB
mutant lacking this crucial His-717 site does not necessarily exhibit a
null phenotype with respect to ArcB-ArcA signaling. The HPt mutant
appears to maintain an ability to signal ArcA, particularly under
aerobic conditions, which results in a significant repression of
sdh. Based on these and other in vivo results, we propose a
model in which ArcB functions in its own right as a dual-signaling
sensor that is capable of propagating two types of stimuli through two
distinct phosphotransfer pathways.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A Dual-Signaling Mechanism Mediated by the ArcB
Hybrid Sensor Kinase Containing the Histidine-Containing
Phosphotransfer Domain in Escherichia coli
*
Corresponding author. Mailing address: Laboratory of
Molecular Microbiology, School of Agriculture, Nagoya University,
Chikusa-ku, Nagoya 464-8601, Japan. Phone: (81)-52-789-4089. Fax:
(81)-52-789-4091. E-mail:
i45455a{at}nucc.cc.nagoya-u.ac.jp.
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