FIGURE 8.

Mechanistic model for the function of TodS. The binding of effectors, such as toluene, occurs at the N-terminal PAS sensor domain, which stimulates phosphorylation of its neighboring kinase domain. The phosphoryl group is then passed on to Asp-500 of the internal response regulator receiver domain and subsequently to His-760 of the C-terminal kinase domain, which is the site for transphosphorylation of TodT. The C-terminal kinase domain has autokinase activity, and it remains to be elucidated whether this is modulated by potential recognition of a signal by the PAS 2 sensor domain.