Fig. 4. Adaptive MWC model for chemoreceptors reveals origin of sensory diversity and its tuning mechanism.

(A) Schematic for allosteric MWC model of the receptor kinase complex. The effective number of coupled receptor dimers n affects the response of kinase activity a upon a step change in ligand concentration from [L]₀ to [L], through the expression a = (1 + exp (f(n, m*, [L]₀, [L])))⁻¹, where m* is the methylation level of the receptors in the absence of ligand. Both n and m* can vary across cells due to differences in gene expression. (B) Two limiting cases of cell-to-cell variation in the model parameters. Model 1 (red solid lines): m* is fixed, but n varies across cells. Model 2 (blue dotted lines): n is fixed, but m* varies across cells. (C to E) Fits of models 1 and 2 to the distribution of steady-state kinase activity a₀ (C), population-averaged dose-response curves (D), and distribution of logK_1/2 (E). Black corresponds [in (C) and (D)] to measured data and [in (E)] to probability density computed from model fits to cumulative distributions (see fig. S7). Error bars represent 95% bootstrap CIs.