Table 1. Parameter values used to... | Rockefeller University Press

Table 1.

Parameter values used to quantitatively describe the activation of DHPR-coupled RyR1s, ^cRyR1s, (^cP₀), and DHPR-noncoupled RyR1s, ^ncRyR1s (^ncP₀) under different conditions

Parameter	Description	Parameter value
^1pK_Mm	Apparent dissociation constant of Mm⁺ from individual A-sites of ^cRyR1s and ^ncRyR1s	172.1 mM^{^a}
^1pK_L	Ca²⁺ equilibrium dissociation constant from individual SR luminal sites of ^cRyR1s and ^ncRyR1s	346.6 μM^{^a}
^1pK_Mg	Mg²⁺ equilibrium dissociation constant from individual A-sites of ^cRyR1s and ^ncRyR1s	30.65 μM^{^a}
^1pK_CaA	Ca²⁺ equilibrium dissociation constant from individual A-sites of ^cRyR1s and ^ncRyR1s	70 nM^{^a}
^1pP_max	Level of individual A-site activation in ^cRyR1s and ^ncRyR1s when the A-site is occupied by Ca²⁺	0.963^{^a}
^1pP_i	Level of individual A-site activation in ^cRyR1s and ^ncRyR1s when the A-site is free or is occupied by two Mm⁺; ^1pP_i is sensitive to SR luminal Ca²⁺ ([Ca²⁺]_L)	= 0.56 + 0.35/(1 + 0.25 mM/[Ca²⁺]_L)^{^a}
K_in	Apparent Ca²⁺/Mg²⁺ dissociation constant from I1 sites of ^ncRyR1s	0.05 mM^{^b}
^4pK_in	Apparent Ca²⁺/Mg²⁺ dissociation constant from I1 sites of ^cRyR1s when DHPRs are not activated	0.05 mM^{^b}
^4pK_in	Apparent Ca²⁺/Mg² dissociation constant from I1 sites of ^cRyR1s when the DHPRs are activated	1.5 mM^{^c}

Parameter	Description	Parameter value
^1pK_Mm	Apparent dissociation constant of Mm⁺ from individual A-sites of ^cRyR1s and ^ncRyR1s	172.1 mM^{^a}
^1pK_L	Ca²⁺ equilibrium dissociation constant from individual SR luminal sites of ^cRyR1s and ^ncRyR1s	346.6 μM^{^a}
^1pK_Mg	Mg²⁺ equilibrium dissociation constant from individual A-sites of ^cRyR1s and ^ncRyR1s	30.65 μM^{^a}
^1pK_CaA	Ca²⁺ equilibrium dissociation constant from individual A-sites of ^cRyR1s and ^ncRyR1s	70 nM^{^a}
^1pP_max	Level of individual A-site activation in ^cRyR1s and ^ncRyR1s when the A-site is occupied by Ca²⁺	0.963^{^a}
^1pP_i	Level of individual A-site activation in ^cRyR1s and ^ncRyR1s when the A-site is free or is occupied by two Mm⁺; ^1pP_i is sensitive to SR luminal Ca²⁺ ([Ca²⁺]_L)	= 0.56 + 0.35/(1 + 0.25 mM/[Ca²⁺]_L)^{^a}
K_in	Apparent Ca²⁺/Mg²⁺ dissociation constant from I1 sites of ^ncRyR1s	0.05 mM^{^b}
^4pK_in	Apparent Ca²⁺/Mg²⁺ dissociation constant from I1 sites of ^cRyR1s when DHPRs are not activated	0.05 mM^{^b}
^4pK_in	Apparent Ca²⁺/Mg² dissociation constant from I1 sites of ^cRyR1s when the DHPRs are activated	1.5 mM^{^c}

Parameter value derived in Appendix 1 from experimental data of Laver et al. (2004).

Parameter value derived from experimental data of Donoso et al. (2000).

As described in the text, DHPR activation of ^cRyR1s induces a sudden 30-fold rise of ^4pK_in from its resting level in ^cRyR1s, which eases inhibition at the I1-sites of the respective ^cRyR1s.

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