Cooperativity increases with the expression level of CheW.

(A,B) Model fit (A) and FRET data [12] (B) for different expression levels of CheW at 0.7 (dark blue), 0.1 (blue) and 0.01 (azure) times the native level of [W]0. (C) Hill curves were fitted to the model outcome to allow for comparison with experimental results. Hill coefficient pairs (model/experiment) in order of increasing [W] are (3.0/3.0), (4.2/5.0) and (4.6/9.6). (D) The corresponding Hill amplitudes in order of increasing [W] are (0.005/0.006), (0.033/0.036) and (0.049/0.044). (E) Distribution of complex types present at half-maximum concentration for 0.7 (dark blue) and 0.01 (azure) times the native concentration [W]0. Model parameters: Δϵ(QEQE) = −2.42, , , ρ = 3.13, , , and J = −3.81. Parameters are shared with model for variation in [A] (Fig 5).