The Ca_V1.3 channel belongs to the L-type family of Ca²⁺ channels. There are currently four known members in this family. L-type channels provide the main influx pathway for Ca²⁺, an essential, versatile and universal intracellular messenger.

Ca_V1.3, as well as the other members of its family, is comprised of an α1-subunit that serves as the voltage sensitive pore. This subunit is comprised of transmembrane segments S1–S4 and a pore-forming region comprised of S5 and S6 segments together with their connecting linker, which contains helical regions contributing to the formation of the selectivity filter. The α1-subunit associates with other subunits to form hetero-oligomeric complexes. β-subunits are tightly associated at the cytoplasmic face of α1, whereas α2δ subunits are GPI-anchored to the plasma membrane and interact with the extracellular domains of α1. The long cytoplasmic C-terminal region of the α1 subunits serves as an important modulatory domain and is a target of numerous protein–protein interactions.

Ca_V1.3 is expressed in many tissues such as the sinoatrial node, heart atria, neurons, chromaffin cells and pancreatic islets. Currently available calcium channel blocking therapeutic agents block Ca_V1.2 and Ca_V1.3 making it difficult to distinguish between the two. To this day there are no known human diseases resulting from mutations in the CACNA1D gene encoding the Ca_V1.3 α1 subunit. This could be due to the fact that loss-of-function mutations cause no phenotype in the heterozygous state (in mice) but are lethal in the homozygous state^1,2.