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J. Bacteriol., 07 1995, 3771-3780, Vol 177, No. 13
U Voelker, A Voelker, B Maul, M Hecker, A Dufour and WG Haldenwang
sigma B is a secondary sigma factor that controls the general stress
response of Bacillus subtilis. sigma B-dependent transcription is induced
by the activation of sigma B itself, a process that involves release of
sigma B from an inhibitory complex with its primary regulator, RsbW. sigma
B becomes available to RNA polymerase when RsbW forms a complex with an
additional regulatory protein (RsbV) and, because of this, fails to bind
sigma B. Using Western blot (immunoblot) analyses, reporter gene fusion
assays, and measurements of nucleotide pool sizes, we provide evidence for
two independent processes that promote the binding of RsbW to RsbV. The
first occurs during carbon limitation or entry into stationary phase.
Activation of sigma B under these circumstances correlates with a drop in
the intracellular levels of ATP and may be a direct consequence of ATP
levels on RsbW's binding preference. The second activation process relies
on the product of a third regulatory gene, rsbU. RsbU is dispensable for
sigma B activation during carbon limitation or stationary phase but is
needed for activation of sigma B in response to any of a number of
different environmental insults (ethanol treatment, salt or acid shock,
etc.). RsbU, or a process dependent on it, alters RsbW binding without
regard for intracellular levels of ATP. In at least some instances, the
effects of multiple inducing stimuli are additive. The data are consistent
with RsbW being a regulator at which distinct signals from separate
effectors can be integrated to modulate sigma B activity.
Copyright © 1995, American Society for Microbiology
Separate mechanisms activate sigma B of Bacillus subtilis in response to environmental and metabolic stresses
Department of Microbiology, University of Texas Health Science Center at San Antonio 78284-7758, USA.
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