Figure 5.

Prediction of the Ca and InsP₃ dependence of the open probability using the data in Figs. 2 and 3. The 2-IP₃/2-Ca model used for the analysis of the open probability data assumes that the InsP₃-gated Ca channel complex contains four monomers, and that each monomer of the tetrameric channel complex has two InsP₃ binding sites, one Ca binding site for activation of the channel, and one Ca binding site for inhibition of the channel. Details of the model are included in methods.