Figure 2.
Equilibrium binding of 125I-calmodulin to pure InsP3 receptors in the absence and presence of Ca2+. SPA-InsP3 receptor beads were incubated with 125I-calmodulin (3 nM) in the presence of the indicated concentrations of unlabeled calmodulin, first in Ca2+-free medium (•, [Ca2+]m ≈ 2 nM) and then after addition of Ca2+ (○, [Ca2+]m ≈ 30 μM). C denotes the control. Results (means ± SEM) are from three independent experiments.