Fig. 5.
Essential components in skeletal muscle excitation-contraction coupling. Voltage-dependent conformational changes in the α1s subunit of CaV1.1 are transmitted mechanically to RyR1, located in the SR membrane. The CaVβ1 subunit, STAC3, and junctophilin are essential in this process, and all three are anchored to disordered regions of α1S (note: the CaVβ1 subunit is visible in cryoelectron microscopy structures of CaV1.1, but has poor local resolution, indicating its mobility). Possibly, all three may become immobilized upon interactions with RyR1 that remain to be identified.