FIGURE 3.

Diagram of SigB regulatory pathways of general stress response under stress conditions in Bacillus subtilis. Energy stress activates the PP2C-type phosphatase RsbP (P for simplicity) and the agonist protein RsbQ (Q for simplicity) which form a complex RsbQP (QP for simplicity) to dephosphorylate RsbV∼Pi (V∼P). Environmental stress induces the kinase activity of RsbT (T for simplicity) to phosphorylate RsbRA (RA∼P), RbsRB (RB∼P), and RsbS (S∼P). Released T from the stressosome binds and activates the PP2C-type phosphatase RsbU (U for simplicity) to dephosphorylate RsbV∼Pi (V∼P). Dephosphorylated RsbV (V), formed by the phosphatases P and/or U, binds to RsbW (W for simplicity), releasing SigB (σ^B) which in turn binds to RNAP and activates its target genes (i.e., GSR and spo0E). A third SigB activating pathway by low temperature stress operates independently of U, P, and V activities at the level of complex stability between RsbW and SigB (Wσ^B). The RbsX phosphatase is responsible for the dephosphorylation of RsbRA∼Pi, RsbRB∼Pi, and RsbS∼Pi, to restore the levels of SigB activity to the ones present before stress (not shown for simplicity). See the text for further details.