Stress Responsive PP2Cs in Bacillus subtilis

Bacillus subtilis has five PP2C-like phosphatases, SpoIIE, PrpC, RsbU, RsbX, and RsbP, with the latter three involved in the regulation of the general stress-responsive oB factor. The oB transcription factor can be activated by energy stress (i.e., starvation of carbon, phosphate, or oxygen) or environmental stress (i.e., high salt, heat shock, or ethanol), leading to the induction of many stress-response genes [27]. Energy and environmental stresses are transmitted by distinct signaling cascades, which are linked by the RsbV anti-anti-o factor (Fig. 2). Energy stress signaling is mediated by the RsbP phosphatase dephosphorylating RsbV to induce the general stress response through inhibition of the anti-o factor RsbW [28]. Environmental stress signals are conveyed through dephosphorylation of RsbV by the RsbU phosphatase, which is activated by upstream regulators, including the RsbX phosphatase [29]. In the absence of

Figure 2 Stress signaling in B. subtilis. The anti-anti-c factor RsbV is dephosphorylated by two PP2C-like phosphatases, RsbP and RsbU, which are activated upon energy or environmental stress, respectively. Dephosphorylated RsbV binds to the RsbW anti-c factor to release cB. Free cB then induces a set of stress responsive genes. RsbW also has a protein kinase activity that phosphorylates and inactivates RsbV.

Figure 2 Stress signaling in B. subtilis. The anti-anti-c factor RsbV is dephosphorylated by two PP2C-like phosphatases, RsbP and RsbU, which are activated upon energy or environmental stress, respectively. Dephosphorylated RsbV binds to the RsbW anti-c factor to release cB. Free cB then induces a set of stress responsive genes. RsbW also has a protein kinase activity that phosphorylates and inactivates RsbV.

stress, the kinase activity of the RsbW anti-c factor represses the pathway via phosphorylation of RsbV.

RsbP contains a PP2C-like catalytic domain as well as a PAS domain essential for its function in vivo. In bacteria, PAS domains with associated chromophores are found in a variety of signal transduction proteins, regulating the activity of a linked output domain in response to changes in the redox potential. The expression level of RsbP is not regulated in response to the energy stress [28], and it is possible that the stress signals modulate the phosphatase activity of RsbP through its PAS domain.

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