Figure 3.

InsP₃R channel gating parameters observed in various [Ca²⁺]_i and [InsP₃] as tabulated (in μM). All parameters plotted were evaluated using event-based statistics (See Appendix). (A) Channel open probability P _o. (B) Channel open probability in each of the three channel gating modes (M stands for H, I, or L, depending on the mode involved). Parameters for the H, I, and L modes are plotted in bar graphs (B–D) in green, yellow, and red, respectively, as indicated by the Key on the upper right corner. (C) Relative prevalence π^M (amount of time the channel spent in a mode/total duration of all analyzed channel current records) for the three gating modes. (D) Relative frequency f ^M (number of times the channel entered a mode/total numbers of modal transitions in all current records) of the gating modes. (E) Mean channel opening 〈t _o〉 (open diamonds) and closing 〈t _c〉 (filled diamonds) duration overall. (F–I) Mean durations of channel opening closing bursts and burst-terminating gaps respectively, for the gating modes. Error bars in bar graphs (A and B) are too small to be plotted noticeably, and those in graphs (E–I) are smaller than the symbols (see Appendix). (J) Mean duration 〈τ ^M〉 of the gating modes. Color and symbols used in graphs (F–J) for the gating modes are tabulated in the key on the upper right corner. Note that in graphs (E–J), the gating kinetic parameters for optimal channel activity ([Ca²⁺]_i = 1 μM and [InsP₃] = 10 μM) are plotted in the left panel for varying [Ca²⁺]_i as well as in the right panel for varying [InsP₃] for easier comparison. Parameters marked with asterisks are those observed in suboptimal ligand concentrations that are statistically significantly different from those observed in optimal [Ca²⁺]_i (1 μM) and saturated [InsP₃] (10 μM).