Descriptions of different models based on different regulation hypotheses.

Each numbered row corresponds to a particular model (hypothesis). The second column shows the parameters that are regulated by the signal σ. The fitted parameters shown in the third column are the parameters varied to minimize the mean error χ2, Eq (5), whose values are given in the last column. The Kp/D parameter is present when a different dissociation constant is used for nanodiscs from that used for the vesicles. The koff/0 is the residue activity level of the “inactive” state. The fourth column shows the fixed large rate constants for the fast reactions in the corresponding model (see text for explanation). Ntotal is the total number of fitting parameters; it is the sum of the number of parameters in the second column plus the 12 parameters common to all models shown in the bottom row. The definitions of the symbols used in this table can be found in Table A of the S1 Appendix.