Dependence of apparent state-to-state transition rate constants on the concentration of ligands. Apparent rate constants plotted against the concentration of Arg⁺ or Agm²⁺, obtained as described in Results. All data are presented as mean ± SEM. The symbols for (forward) or (backward) rate constants, k_i,j or k_j,i, are colored blue or red in the case of Arg⁺, whereas they are colored green or orange in the case of Agm²⁺. The curves superimposed on the data are fits of an equation with the same form as Eq. 3. Fitted parameter values are given in Tables S1, S2, S3, and S4.