New Family of Regulators in the Environmental Signaling Pathway Which Activates the General Stress Transcription Factor ς ^B of Bacillus subtilis

Novel σ B regulation modules of Gram-positive bacteria involve the use of complex hybrid histidine kinases

“…Energy stress is probably signalled through RsbP, which contains an N-terminal PAS sensory domain (Brody et al, 2001(Brody et al, , 2009Vijay et al, 2000), while environmental stress (i.e. heat, osmolytes, ethanol, low pH) is signalled through RsbU, which contains an N-terminus that interacts with the regulator RsbT, which in turn interacts with the RsbRand RsbS-containing supramolecular 'stressosome' (Akbar et al, 2001;Chen et al, 2003;Delumeau et al, 2006;Dufour et al, 1996;Kim et al, 2004;Marles-Wright et al, 2008) (Fig. 1a).…”

“…The B. subtilis stressosome is an~1.8 MDa supramolecular complex that consists of multiple copies of RsbR and RsbS (Chen et al, 2003;Delumeau et al, 2006;Dufour et al, 1996;Marles-Wright et al, 2008). Different environmental stresses and signals are thought to stimulate RsbT kinase activity towards its stressosome substrates (Akbar et al, 2001;Á vila-Pé rez et al, 2006;Gaidenko et al, 2006;Kim et al, 2004;Voelker et al, 1995). This leads to dissociation of RsbT from the stressosome to activate RsbU and subsequently s B .…”

Enhancement of a σB-dependent stress response in Bacillus subtilis by light via YtvA photoreceptor

“…s B is activated by occurrence of several environmental stresses, such as salt, ethanol-addition and heat shock, as well as energy stress like entry into the stationary phase of growth, and these Rsb proteins involve in receiving and transmitting environmental stress signals. As ytvA deletion resulted in reduction of s B activation by several stresses, YtvA is also recognized as a positive regulator of s B activity (Akbar et al, 2001), but precise mechanism for this regulation is not known. It is noteworthy that YtvA is distinctive from others in that it does not contain phosphorylation sites by RsbT kinase, and only YtvA contains LOV domain (Akbar et al, 2001).…”

“…YtvA belongs to a family of six proteins in B. subtilis, RsbRA, RsbRB, RsbRC, RsbRD (formerly RsbR, YkoB, YojH and YqhA, respectively), RsbS and YtvA, which share extensive similarities with each other at their C-terminal STAS domains (Akbar et al, 2001). These five Rsb proteins are members of regulators of s B activity, a stress response sigma factor.…”

Light-induced behavioral responses (‘phototaxis’) in prokaryotes

“…It is relevant to note that this organism has a protein with sequence similarity to UV-A/blue light photoreceptors. Akbar et al (2001) have shown that one of the upstream components in the stress-signaling pathway in B. subtilis that activates sigma factor B, YtvA, has considerable sequence identity with the chromophore-binding domain of the phototropin photoreceptors from plants. Upon heterologous overexpression in E. coli the YtvA protein indeed turned out to carry a flavin-type chromophore.…”