![Figure 5. The concentration dependence of activation of the RYR2 channel by ATP analyzed by the allosteric gating model. (A) Values of PO for 0.005, 1, 8, 15, 26, and 53 mM [Ca2+]L (black squares; open circles; black, gray, and open triangles; and black diamonds, respectively) are displayed as a function of ATP concentration. Solid lines are the best fits by Eq. 3. (B) Values of Po for [Ca2+]C of 100, 180, 250, 330, and 410 nM (open circles; black, gray, and open triangles; and black diamonds, respectively) are displayed as a function of ATP concentration. Solid lines are the best fits by Eq. 3. (C) The relationship between KO0 and fATP at different [Ca2+]L (solid symbols) and [Ca2+]C (open symbols). Solid lines are the apparent linear fits of the data for variable [Ca2+]L in the two ranges of 0.005–8 mM (R = 0.99 and P = 0.066) and 8–53 mM (R = −0.62 and P = 0.37). Dashed line is the apparent linear fit of the data for variable [Ca2+]C (R = 0.97 and P < 0.01). Note that the point representing 1 mM [Ca2+]L and 100 nM [Ca2+]C (partially filled circle) was included in both fits. (D) The relationship between tO0 and fATP at different [Ca2+]L (closed symbols) and [Ca2+]C (open symbols). Solid lines are the apparent linear fits of the data, with R = 0.99 (P < 0.005) for variable [Ca2+]L and R = 0.50 (P > 0.35) for variable [Ca2+]C. Note that the point representing 1 mM [Ca2+]L and 100 nM [Ca2+]C (partially filled circle) was included in both fits. In C and D, labels next to the points specify the conditions of the experiments (L0.005, L1, L15, and L53 for [Ca2+]L of 0.005, 1, 15, and 53 mM, respectively, and C100, C250, and C410 for [Ca2+]C of 100, 250, and 410 nM, respectively).](https://cdn.rupress.org/rup/content_public/journal/jgp/140/2/10.1085_jgp.201110708/4/jgp_201110708r_fig5.jpeg?Expires=1773509698&Signature=ODk9dUS2HOZFka~0erW~d2ttK-Q8-hODYR6yfP7Lquyg6otkY~wRHPkT~2dovO1zXaZRpSPLJXo~froHXfLRXAZi6TRYX~NtNnZOPz7RLHfBAqGX5dp8xWsWqUjWLmPpGFDXbH~hrIsP96xoMoCqrePHwJ6jIclhS2~emhvvE2cws~lvDhR9HV1TgbOHjDuGfzEIlBWSSqq82WoG5oMvACtaJZtPDusF7mDkJItEkprqXavptnNIC4a~Z-nQseKAsTnD2utHgnqIoT5sOw5tl1Cx5dXcr~q9rylIEXihBCkeD2doT204nW9ZkmMhBikt2KVEesTv80KNPwISME22mg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
The concentration dependence of activation of the RYR2 channel by ATP analyzed by the allosteric gating model. (A) Values of PO for 0.005, 1, 8, 15, 26, and 53 mM [Ca2+]L (black squares; open circles; black, gray, and open triangles; and black diamonds, respectively) are displayed as a function of ATP concentration. Solid lines are the best fits by Eq. 3. (B) Values of Po for [Ca2+]C of 100, 180, 250, 330, and 410 nM (open circles; black, gray, and open triangles; and black diamonds, respectively) are displayed as a function of ATP concentration. Solid lines are the best fits by Eq. 3. (C) The relationship between KO0 and fATP at different [Ca2+]L (solid symbols) and [Ca2+]C (open symbols). Solid lines are the apparent linear fits of the data for variable [Ca2+]L in the two ranges of 0.005–8 mM (R = 0.99 and P = 0.066) and 8–53 mM (R = −0.62 and P = 0.37). Dashed line is the apparent linear fit of the data for variable [Ca2+]C (R = 0.97 and P < 0.01). Note that the point representing 1 mM [Ca2+]L and 100 nM [Ca2+]C (partially filled circle) was included in both fits. (D) The relationship between tO0 and fATP at different [Ca2+]L (closed symbols) and [Ca2+]C (open symbols). Solid lines are the apparent linear fits of the data, with R = 0.99 (P < 0.005) for variable [Ca2+]L and R = 0.50 (P > 0.35) for variable [Ca2+]C. Note that the point representing 1 mM [Ca2+]L and 100 nM [Ca2+]C (partially filled circle) was included in both fits. In C and D, labels next to the points specify the conditions of the experiments (L0.005, L1, L15, and L53 for [Ca2+]L of 0.005, 1, 15, and 53 mM, respectively, and C100, C250, and C410 for [Ca2+]C of 100, 250, and 410 nM, respectively).
