Figure 1. Model of the stressosome previously characterized in B. subtilis.

In the absence of stress, RsbT (turquoise) only phosphorylates RsbR (purple), resulting in basal transcription level (top). In the presence of an environmental stressor, RsbT continues to phosphorylate RsbR; increasing levels of RsbR phosphorylation causes RsbS (blue) to also be phosphorylated by RsbT. Phosphorylated RsbS reduces the binding affinity of RsbT to the stressosome core, causing RsbT to activate downstream stress response gene transcription through a cascade that activates σ^B (bottom)¹⁵,¹⁶.