Nomenclature and tissue distribution

Ten specific mammalian calcium channel subtypes have been identified based on the sequence of their membrane pore-forming oq subunit. As illustrated in Table 1, calcium channels may be individually identified by their oq subunit, or more commonly using a systematic nomenclature based on a gene subfamily (Cavl-Cav3) and the order of discovery of the oq subunit (e.g., Cavl.l-Cav 1.4) [7]. 

The pore-forming oq subunit alone is sufficient to form a functional calcium channel in the cell membrane [8]. However, high-voltage-activated calcium channels are hetero-oligomeric structures that may contain as many as three additional smaller subunits, labeled CX25 (itself a heterodimer), (5, and y. These three subunits associate in an auxiliary 

P/Q-type Cav2.1 t lA Neuron presynaptic terminals, heart, brain 

R-type Cav2.3 OllE Neuron cell bodies and presynaptic terminals, heart, pituitary 

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