RyR2 channels gating together retain their sensitivity to Ca ²⁺ . Rat cardiac microsomes reconstituted in bilayers. Ca²⁺ currents flowing from trans to cis driven by a similar [Ca²⁺]_trans as in Fig. 1. (A and B) Panels A and B show currents from channels in a low-activity and a high-activity category, respectively, differing in P_open at physiological [Ca²⁺]_cis by more than an order of magnitude. The activation by [Ca²⁺]_cis has similar half-effect concentrations and maximal activations in both categories, also similar to those found with independently gating channels. Note here clear transitions to the CO/OC configuration, frequent starting from OO but essentially absent starting from CC. Figure minimally modified from Fig. 2 of Gaburjaková and Gaburjaková (2010), reproduced by courtesy of Marta and Jana Gaburjaková. Fig. 2 is reprinted with permission from Springer Nature.