Module 3: Figure CaV1.1 L-type channel
Molecular organization of the CaV1.1 L-type channel from skeletal muscle.
The pore-forming α1S subunit is made up four repeated domains (I–IV) each containing six transmembrane segments (S1–S6). Located between segments S5 and S6 is an additional loop that embeds itself in the membrane to form the channel pore. The intracellular β subunit, which binds strongly to an α1-interaction domain (AID) on the cytosolic loop between domains I and II, has four α-helices, but no transmembrane regions. A region of the cytoplasmic loop between domains II and III (marked in blue) interacts with the ryanodine receptor type 1 (RYR1). The γ subunit is embedded in the membrane through four transmembrane segments. Finally, there is an α2 subunit, which is extracellular and remains associated with the receptor complex through its linkage by a disulphide bond to the δ subunit, which is embedded in the membrane through a single transmembrane segment.