The alpha-2/delta subunit of voltage-dependent calcium channels regulates calcium current density and activation/inactivation kinetics of the calcium channel. Plays an important role in excitation-contraction coupling (By similarity). Dimer formed of alpha-2-1 and delta-1 chains; disulfide-linked. Voltage-dependent calcium channels are multisubunit complexes, consisting of alpha-1 (CACNA1), alpha-2 (CACNA2D), beta (CACNB) and delta (CACNA2D) subunits in a 1:1:1:1 ratio (By similarity). Isoform 2A is expressed in skeletal muscle and aorta. Isoform 2B is expressed in brain. Isoform 2C is expressed in heart. Isoform 2D is expressed in heart and smooth muscle. Isoform 2E is expressed in smooth muscle. All five isoforms are expressed in the cardiovascular system. The MIDAS-like motif in the VWFA domain binds divalent metal cations and is required to promote trafficking of the alpha-1 (CACNA1) subunit to the plasma membrane by an integrin-like switch. Proteolytically processed into subunits alpha-2-1 and delta-1 that are disulfide-linked. Binds gabapentin, an antiepileptic drug. Belongs to the calcium channel subunit alpha-2/delta family.