__ Big Calcium Summary Journal of General Physiology JGP with Cover May 2009 comp3.pdf (original) (raw)

Voltage-dependent calcium channels relay electrical signals from the cell membrane to the cytoplasm by allowing extracellular Ca 2+ to flow into the cell, where Ca 2+ acts as a chemical signal . The Ca 2+ -conducting pore of these transmembrane proteins selects Ca 2+ over the much more abundant cations Na + and K + . Four amino acid residues bearing acidic side chains (the "EEEE" locus in L-type calcium channels) extend into this pore, and all cooperate in selecting Ca 2+ with high affinity for review see . Here, we compute consequences of a physical model of selectivity in which ions compete for interaction with negative structural charge and for restricted space in the EEEE locus.