Modulation of TodS autophosphorylation activity in vitro. TodS autophosphorylation activity with [32P]ATP was measured in the absence of signal (control) and in the presence of 100 μM toluene, o-xylene, 1,2,3-TMB, or o-chlorotoluene. (A) SDS/PAGE of TodS in the absence and presence of different ligands. (B) Densitometric analysis of the data in A. Data are the means of three independent assays. Linear fit of the points at 2.5 and 10 min was used to calculate relative rates of autophosphorylation. Filled square, control; open triangle, o-chlorotoluene; open square, trimethylbenzene; open diamond, o-xylene; filled diamond, toluene.