Table 2.

Rate and equilibrium constant values obtained from the global fits of MWC and MWC + Open models to single-channel data sets

Rate and equilibrium constants Unit MWC (Scheme 1) MWC + Open (Scheme 1a) 
α3′ s−1  167 ± 9% 
β3′ s−1  6,450 ± 14% 
α1 s−1 60 ± 63% 86,300 ± 100% 
β1 s−1 0.147 ± 71% 7 ± 100% 
α2 s−1 3,150 ± 27% 101,200 ± 49% 
β2 s−1 2,730 ± 10% 5,480 ± 68% 
α3 s−1 46 ± 7% 2,100 ± 16% 
β3 s−1 31,400 ± 5% 15,300 ± 32% 
k+ M−1 s−1 2.54 × 104 ± 10% 2.15 × 104 ± 67% 
k s−1 163 ± 7% 58 ± 63% 
ko+ M−1 s−1 1.40 × 106 ± 24% 9.97 × 107 ± 96% 
ko− s−1 13.3 ± 41% 93 ± 51% 
E1 = β11  0.0016 ± 42% 0.0002 ± 82% 
E2 = β22  1.0 ± 29% 0.04 ± 69% 
E3 = β33  700 ± 11% 7.9 ± 35% 
E3′ = β3′/α3′   38.6 ± 11% 
KR = k/k+ mM 6.4 ± 5% 6.3 ± 11% 
Ko = ko−/ko+ mM 0.0092 ± 24% 22.9 ± 64% 
EC50 mM 0.81 ± 3% 1.14 ± 6% 
nH  2.6 ± 1% 2.5 ± 2% 
Rate and equilibrium constants Unit MWC (Scheme 1) MWC + Open (Scheme 1a) 
α3′ s−1  167 ± 9% 
β3′ s−1  6,450 ± 14% 
α1 s−1 60 ± 63% 86,300 ± 100% 
β1 s−1 0.147 ± 71% 7 ± 100% 
α2 s−1 3,150 ± 27% 101,200 ± 49% 
β2 s−1 2,730 ± 10% 5,480 ± 68% 
α3 s−1 46 ± 7% 2,100 ± 16% 
β3 s−1 31,400 ± 5% 15,300 ± 32% 
k+ M−1 s−1 2.54 × 104 ± 10% 2.15 × 104 ± 67% 
k s−1 163 ± 7% 58 ± 63% 
ko+ M−1 s−1 1.40 × 106 ± 24% 9.97 × 107 ± 96% 
ko− s−1 13.3 ± 41% 93 ± 51% 
E1 = β11  0.0016 ± 42% 0.0002 ± 82% 
E2 = β22  1.0 ± 29% 0.04 ± 69% 
E3 = β33  700 ± 11% 7.9 ± 35% 
E3′ = β3′/α3′   38.6 ± 11% 
KR = k/k+ mM 6.4 ± 5% 6.3 ± 11% 
Ko = ko−/ko+ mM 0.0092 ± 24% 22.9 ± 64% 
EC50 mM 0.81 ± 3% 1.14 ± 6% 
nH  2.6 ± 1% 2.5 ± 2% 

The fits constrain the binding and unbinding rates to be the same, regardless of the number of molecules bound and the conformation. Those constraints were implemented by the following equations: k+1 = k+2 = k+3 = k+; k−1 = k−2 = k−3 = k and ko+2 = ko+3 = ko+; ko−2 = ko−3 = ko−. In addition, one rate constant in each cycle was fixed by the constraint of microscopic reversibility (Colquhoun et al., 2004). The equilibrium constants, E and K, and the values for the EC50 and Hill slope (nH) of the predicted Popen curve were calculated from the rate constants for each set and then averaged. Values are means ± coefficient of variation (i.e., SD of the mean expressed as a percentage of the mean).

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