In cardiac myocytes, the L-type calcium channel passes inward Ca2+ current and triggers calcium release from the sarcoplasmic reticulum by activating ryanodine receptor 2 (RyR2) (calcium-induced-calcium-release). Phosphorylation of these channels increases their permeability to calcium and increases the contractility of their respective cardiac myocytes.
In skeletal muscle, there is a very high concentration of L-type calcium channels, situated in
the T-tubules. Muscle depolarization results in large gating
currents, but anomalously low calcium flux, which is now
explained by the very slow activation of the ionic currents. For
this reason, little or no Ca2+ passes across the T-tubule
membrane during a single action potential.
Like most voltage-gated ion channels, the α-subunit is composed of 4 subunits. Each subunit is formed by 6 alpha-helical, transmembrane domains that cross the membrane (numbered S1-S6). The S1-S4 subunits make up the voltage sensor, while S5-S6 subunits make up the selectivity filter.
Alpha subunit of a generic voltage-gated ion channel
^ abFelizola SJ, Maekawa T, Nakamura Y, Satoh F, Ono Y, Kikuchi K, Aritomi S, Ikeda K, Yoshimura M, Tojo K, Sasano H (2014). "Voltage-gated calcium channels in the human adrenal and primary aldosteronism". J Steroid Biochem Mol Biol. 144 (part B): 410–416. doi:10.1016/j.jsbmb.2014.08.012. PMID25151951.
^Yamakage M, Namiki A (February 2002). "Calcium channels--basic aspects of their structure, function and gene encoding; anesthetic action on the channels--a review". Canadian Journal of Anesthesia. 49 (2): 151–64. doi:10.1007/BF03020488. PMID11823393.