Module 3: Figure VOC subunits

Structural organization of the VOC subunits.

The channel complex is based on the large α1 subunit, which contains the pore region, voltage sensor and binding sites for Ca2+ and drugs such as dihydropyridine (DHP). The large cytoplasmic loop (*) on some α1 subunits function to link channels to synaptic vesicles or the type 1 ryanodine receptor (RYR1) of skeletal muscle. The extracellular α2 subunit has numerous glycosylation sites and is linked through a disulphide bond to a δ subunit that has a single transmembrane region. The variable γ subunit is another transmembrane protein. Finally, there is an intracellular β subunit, which seems to alter the function of different channels and is the target of some of the modulatory signalling pathways (e.g. Module 3: Figure CaV1.1 L-type channel).