The alpha-2/delta subunit of voltage-dependent calcium channels regulates calcium current density and activation/inactivation kinetics of the calcium channel. Dimer formed of alpha-2-2 and delta-2 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 (Probable). Interacts with CACNA1C and CACNB3 (By similarity). 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. May be proteolytically processed into subunits alpha-2-4 and delta-4 that are disulfide-linked. It is however unclear whether such cleavage really takes place in vivo and has a functional role (By similarity). Defects in Cacna2d4 are a cause of cone-rod dysfunction. Mice display affected retinal ribbon-type synapses. The retinopathy is accompanied by a substantial loss in the activities of the second-order neurons. Rod photoreceptor responses are maintained with reduced amplitude, whereas cone activities are absent. Belongs to the calcium channel subunit alpha-2/delta family.