Table 1.

Distances between the Tb³⁺ and Bodipy FL probes during the catalytic cycle of NT Pgp

The measurements in the absence of Ver were obtained first for the apo-state and then after sequential addition of 5 mm NaATP (ATP-bound state), 10 mm MgSO₄ (MgATP state), and 0.25 mm V_i (V_i state). In the presence of Ver, measurements were obtained first for the apo-state and then after sequential addition of Ver (Ver-bound state), 5 mm NaATP (Ver/ATP-bound state), 10 mm MgSO₄ (Ver/MgATP state), and 0.25 mm V_i (Ver/V_i state). The two dominant exponential components of the sensitized emission decays are presented as distances d1 and d2. Lifetimes of Bodipy FL-sensitized emission (τ_DA), the calculated donor-acceptor distances (R), and the percentage of NT Pgp molecules displaying each distance are shown. The latter were calculated from multiexponential fits as the fractional intensity contribution of each exponential component divided by the rate of energy transfer (k = 1/τ_DA − 1/τ_D). Data are presented as means ± S.E., and n is the number of independent experiments. All the LRET decays used for these calculations were obtained from NT Pgp in NDSCs at 37 °C.

State	d1			d2
	τDA	R1	Molecules	τDA	R2	Molecules
	μs	Å	%	μs	Å	%
NT Pgp in NDSCs in the absence of transport substrate (n = 7)
Apo	378 ± 12	32.7 ± 0.2	12 ± 1	1286 ± 18	47.1 ± 0.4	88 ± 1
ATP-bound	369 ± 11	32.5 ± 0.2	40 ± 4	1212 ± 11	45.6 ± 0.2	60 ± 4
MgATP	414 ± 13	33.3 ± 0.2	29 ± 2	1282 ± 19	47.0 ± 0.4	71 ± 2
Vi	439 ± 16	33.7 ± 0.3	49 ± 4	1088 ± 34	43.6 ± 0.5	51 ± 4
NT Pgp in NDSCs in the presence of 30 μm verapamil (Ver; n = 5)
Apo	373 ± 11	32.6 ± 0.2	12 ± 1	1265 ± 37	46.7 ± 0.8	88 ± 1
Ver-bound	389 ± 16	32.9 ± 0.3	17 ± 1	1136 ± 13	44.3 ± 0.2	83 ± 1
Ver/ATP-bound	349 ± 20	32.1 ± 0.4	24 ± 3	1150 ± 11	44.5 ± 0.2	76 ± 3
Ver/MgATP	394 ± 17	33.0 ± 0.3	39 ± 4	1164 ± 33	44.8 ± 0.6	61 ± 4
Ver/Vi	430 ± 28	33.6 ± 0.5	46 ± 6	1119 ± 32	44.0 ± 2.0	54 ± 6