Figure 2. Model for the Phosphorylation Cascade in B. subtilis .

The model assumes that the receptor complex (receptor, CheA, CheC, CheD, and CheW) exists either in an active (T^A) or inactive (T^I) state. Active receptors stimulate CheA. CheA phosphorylates CheB, CheV, and CheY. Phosphorylated CheY (Y_p) binds the receptor and increases the likelihood a receptor adopts an inactive conformation (thick red line). Phosphorylated CheY also binds the flagellar motor (M). The motor switch enhances the rate of CheY dephosphorylation (Szurmant et al. 2003). The model assumes that unphosphorylated CheV inhibits CheA by disrupting the receptor complex (thick blue line).