Phosphate Sink Containing Two-Component Signaling Systems as Tunable Threshold Devices
Figure 3
Experimental validation for the role of the sink RR in shaping the signal-response curve.
The steady-state level of phosphorylated CheY2 was measured in the presence or absence of the sink (i.e. CheY1) at different 32P-ATP concentrations. (A) Phosphorimages showing phosphorylated CheY2 levels in the presence or absence of CheY1 at low (0.2 mM) and high (2 mM) ATP levels. The indicated quantity of [γ-32P] ATP was added to a reaction mixture containing 10 µM CheA, 2.5 µM CheY2, and where indicated 2.5 µM CheY1. (B) Graph comparing the observed steady state levels of phosphorylated CheY2 with and without the sink, CheY1. The phosphorylated CheY2 levels predicted by the model are shown with a dashed line (in absence of sink) and with a solid line (in presence of sink), while the experimentally measured values are shown by squares (in absence of sink) and circles (in presence of sink). Error bars show the standard error of the mean obtained from three independent experiments.