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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: Cell Calcium. 2019 Feb 12;79:35–43. doi: 10.1016/j.ceca.2019.02.002

Figure 3. Nonlinear effects of STIM1-Orai1 binding on CRAC channel gating and permeation.

Figure 3.

Hexameric CRAC channels (red) bind STIM1 dimers (blue) upon entering ER-PM junctions, but show little activity until five sites become occupied. The quintuplybound channels have altered properties, including reduced Po, Ca2+ blocking affinity, and CDI, and elevated unitary conductance and PCs/PNa compared to the fully bound channel or native CRAC channels. Binding to all six subunits is needed to produce the effective activation and permeation characteristics of native CRAC channels.