Table 2.

Rate constants of block of rI_Na by TTX and recovery from block following simultaneous washout of TTX and peptide

Peptide	[TTX] kobs of block of rINa by TTX		koff of peptide•TTX•NaVa	koff of peptide•NaVb	Estimated konc	Estimated kond
	µM	min−1	min−1	min−1	µM−1•min−1	µM−1•min−1
ddKIIIA	100	0.44 ± 0.13	0.58 ± 0.03	0.01 ± 0.0015	−0.0014 ± 0.0013e	0.0044 ± 0.0013
ddKIIIA[K7A]	10	4.4 ± 1.3	0.27 ± 0.035	0.13 ± 0.03	0.41 ± 0.13	0.44 ± 0.13
ddKIIIA[K7D]	10	1.7 ± 0.4	0.081 ± 0.013	0.083 ± 0.02	0.16 ± 0.04	0.17 ± 0.04
ddKIIIA[K7S]	10	4.6 ± 1.6	0.13 ± 0.015	0.11 ± 0.02	0.45 ± 0.16	0.46 ± 0.16
ddKIIIA[K7F]	10	2.2 ± 0.5	0.27 ± 0.01	0.3 ± 0.04	0.19 ± 0.05	0.22 ± 0.05
ddKIIIA[K7G]	3.3f	6.5 ± 1.0	0.48 ± 0.085	0.67 ± 0.11	1.82 ± 0.3	1.97 ± 0.3
ddKIIIA[K7L]	10	0.73 ± 0.06	0.17 ± 0.01	0.2 ± 0.009	0.056 ± 0.006	0.073 ± 0.006
ddKIIIA[K7V]	10	1.2 ± 0.05	0.082 ± 0.01	0.091 ± 0.014	0.11 ± 0.005	0.12 ± 0.005
ddKIIIA[K7T]	10	1.3 ± 0.2	0.1 ±0.009	0.09 ± 0.006	0.12 ± 0.02	0.13 ± 0.02
ddKIIIA[K7dap]	3.3f	1.8 ± 0.5	0.55 ± 0.02	0.06 ± 0.008	0.38 ± 0.15	0.54 ± 0.15
KIIIAg	NA	NA	0.017 ± 0.002	0.0016 ± 0.0016	0.3 ± 0.03h	NA
KIIIA[K7A]g	NA	NA	0.024 ± 0.004	0.015 ± 0.005	0.13 ± 0.006h	NA
KIIIA[K7D]	10	2.3 ± 0.6	0.01 ± 0.003	0.008 ± 0.001	0.23 ± 0.06	0.23 ± 0.06

^aRate constant of recovery from block of ternary complex, peptide•TTX•Na_V1.2, when both peptide and TTX were simultaneously washed out.

^bBinary complex values from Table 1, reproduced here for ready comparison with ternary complex values.

^cCalculated assuming bimolecular reaction kinetics (k_on = (k_obs − k_off)/[TTX]) and TTX dissociated from the ternary peptide•TTX•Na_V complex with a rate constant no larger than the k_off of peptide•TTX•Na_V (i.e., 5^th column in table). Rationale for this assumption is that if during the washout of both toxins TTX dissociated from the complex before peptide did, then a rapid recovery of rI_Na would be expected, followed by the slower recovery from block by peptide alone; instead, the recovery from block followed essentially a single exponential time course (see Figs. 4C & D). For the most part, the k_off value for a given ternary peptide•TTX•Na_V complex was either larger or approximately equal to the k_off value for the corresponding binary peptide•Na_V complex (compare columns 4 and 5).

^dUpper limit of k_on obtained by assuming TTX could not dissociate from the ternary complex, in which case estimated k_on = k_obs/[TTX]. Note, both k_on estimates gave similar values.

^eNegative value for estimated k_on suggests k_off of recovery from block of the ternary complex is a gross overestimate of k_off of TTX in this instance.

^fLower concentration than elsewhere was used because of larger relative k_obs.

^gData from ref. (18).

^hObtained from slope of k_obs versus [ligand] plot.