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. 2019 Apr 22;17(4):e3000096. doi: 10.1371/journal.pbio.3000096

Fig 5. Proposed mechanism of Orai channel activation and Ca2+ permeation.

Fig 5

Two opposite subunits of the Orai channel are shown. Ca2+ and anions are drawn as red and green spheres, respectively. In the closed state, the latched TM4 helix limits the opening of the pore on the cytosolic side. Upon activation, the swing of the TM4 helix induces an outward twist of the pore on the cytosolic side, thus aggregating anions. These anions may reduce positive charge repulsion and increase the potential gradient across the membrane, allowing Ca2+ permeation. TM, transmembrane.