Voltage-gated calcium (CaV) channels catalyse rapid, highly selective influx of Ca2+ into cells despite a 70-fold higher extracellular concentration of Na+. How CaV channels solve this fundamental biophysical problem remains unclear.
Ca2+ ions flow through CaV channels at a rate of ~1 million ions per second, yet Na+ conductance is >500-fold lower. Such high-fidelity, high-throughput CaV channel performance is important in regulating intracellular processes such as contraction, secretion, neurotransmission and gene expression in many different cell types. Because the extracellular concentration of Na+ is 70-fold higher than Ca2+, these essential biological functions require CaV channels to be highly selective for Ca2+ in preference to Na+, even though Ca2+ and Na+ have nearly identical diameters (~2 Å). (Nature 505, 56–61 (02 January 2014) doi:10.1038/nature12775)