TABLE 1.

Equations and parameters of the luminal-triggered Ca²⁺ feedthrough model

Eq.		Eq.
	L-site
2		3	β′=β		Affinity	Opening (0V)	V-dependence	Closing
				+ATP	KL = 60 μM	α = 2.7 s−1	Δ = 0.4	β = 1000 s−1
				−ATP	KL = 45 μM	α = 0.6 s−1	Δ = 0.4	β = 1000 s−1
	A-site
4		5			Affinity	Opening	Feedthrough	Closing
				+ATP	KA = 1 μM	γ = 43 s−1μM−3	X = 15 μM/pA	δ = 220 s−1μM (n = 1)
6		7a,		−ATP	KA = 6 μM	γ = 1.0 s−1μM−3	X = 15 μM/pA	δ = 700 s−1 (n = 0)
		7b
	I2-site
8		9	ϕ′=ϕ		Affinity	Closing	Feedthrough	Opening
				+ATP	KI = 1.2 μM	θ = 250 s−1	Y = 0.35 μM/pA	ϕ = 300 s−1
10a		10b		−ATP	KI = 1.2 μM	θ = 800 s−1	Y = 0.35 μM/pA	ϕ = 400 s−1

Equations describe the [Ca²⁺]-dependencies of opening and closing rates associated with each site (refer to Scheme IV in Fig. 1 B). K_A was derived from the theoretical half-maximal [Ca²⁺]_C-activation of P_o and was not used in the fitting of the model. The reaction rates are distinguished from model parameters with an apostrophe (e.g., α′). γ′, δ′, and θ′ depend on the Ca²⁺ current through the pore and therefore take on different values for the open and closed states (indicated by subscripts, o and c). In Eq. 2, T is the temperature in degrees K, k is the Boltzmann constant and V is bilayer voltage.