Fig. 4.

Transition from regime I to regime II for homogeneous receptors. Response of homogeneous clusters of Tar receptors to steps of MeAsp within the MWC model. Dose–response curves (solid) and receptor-occupancy curves (dashed) are shown for Tar receptor methylation states EEEE, QEEE, QEQE, and QEQQ (left to right), where the Tar-receptor parameters and cluster sizes are those used in Fig. 1b. (Inset Upper) Adaptation of averaged activity is shown of a cluster Tar receptors exposed to two steps of MeAsp from 0 mM up to 1 mM at t = 30 s and then down to 0.01 mM at t = 90 s. (Inset Lower) Average methylation level of receptors. Averages are taken over 100 independent clusters of six Tar receptors. Details of the Barkai-Leibler-type adaptation model (15) are given in supporting information.