TABLE 2.

Inactivation rate constants in whole oocytes

Control		In 0.5 μM κ−PVIIA
	Average ± SE		Average ± SE
kono (μM−1s−1)	50.0	koni (μM−1s−1)	28.3 ± 7.5
koffo (s−1)	25.0	koffi (s−1)	14.0 ± 5.4
ki (s−1)	0.187 ± 0.013	kib (s−1)	0.234 ± 0.074
kr (s−1)	0.049 ± 0.0042	krb (s−1)	0.054 ± 0.016
Ki	0.26 ± 0.0082	Kib	0.37 ± 0.190
κ−PVIIA binding constants
Open channels		Inactivated channels
KDo (μM)	0.5	KDi (μM)	0.68 ± 0.35

Kinetic and rate constants that describe Scheme 1 applied to the TEVC relaxation curves as those shown in Fig. 3. Values are the average of four oocytes to which the relaxations in the presence and in the absence of toxin were compared. The strategy to do the fitting is described in Materials and Methods. K_i and K_ib, the apparent inactivation equilibrium constants at 0 mV, were calculated from k_r/k_i and k_rb/k_ib, respectively, whereas K_Do and K_Di were calculated from k_offo/k_ono and k_offi/k_oni, respectively. A value of ΔΔG = +0.2 kcal/mol results from the change in binding energy of the toxin to inactivated channels relative to the binding to open channels.