Table 1. Intra- and intermolecular distances between the Ca_v1.2 calcium channel α_1C and β subunits measured by three-color FRET microscopy.

Channel subunits	Measured distances (r)	β1b	β2d		β3
		r, Å	r, Å	c	r, Å	c
Vα1CC+Rβ	r C-V	68±1 (17)	68±2 (13)	0.90±0.37	69±1 (19)	0.60±0.05
	r C∼V		72±3 (5)	1.27±0.54	77±3 (6)	1.16±0.17
	r V-R	95±3 (13)	99±3§ (8)	1.70±0.27	90±2 (19)	0.97±0.20
	r V∼R		107±1 (3)	2.52±0.17	100±2 (15)	1.72±0.23
	r C-R	85±2‡ (13)	84±2 (13)		79±1 (14)	0.70±0.10
	r C∼R				85±1 (10)	1.55±0.07
Vα1C+α1CC+Rβ	r C∼V	67±1* (26)	72±2 (13)		79±4 (10)
	r V-R	90±2 (26)	90±2 (13)		90±5 (10)
	r C-R	78±1† (26)	86±2 (6)		80±4 (8)

^* P<0.002 vs. β₃.

^† P<0.05 vs. β_2d.

^‡ P<0.05 vs. β₃.

^§ P<0.05 vs. r _V-R in Vα_1C+α_1CC+Rβ_2d.

FRET efficiency between the indicated fluorophores fused to the α_1C and β_1b, β_2d or β₃ subunits was measured in the plasma membrane of expressing COS1 cells and fitted to a Gaussian function. In cases when the routine curve fit showed two significantly different Gaussian distributions, the corresponding dispersion coefficients c (mean±SEM) are shown for both distances (see Experimental Procedures). V – mVenus, C- mCerulean, R – tagRFP. Shown values of r are mean±SEM. Number of cells is shown in parentheses.