Mechanisms of permeation and selectivity in calcium channels.
The mechanisms underlying ion transport and selectivity in calcium channels are examined using electrostatic calculations and Brownian dynamics simulations. We model the channel as a rigid structure with fixed charges in the walls, representing glutamate residues thought to be responsible for ion selectivity. Potential energy profiles obtained from multi-ion electrostatic calculations provide insights into ion permeation and many other observed features of L-type calcium channels. These qualitative explanations are confirmed by the results of Brownian dynamics simulations, which closely reproduce several experimental observations. These include the current-voltage curves, current-concentration relationship, block of monovalent currents by divalent ions, the anomalous mole fraction effect between sodium and calcium ions, attenuation of calcium current by external sodium ions, and the effects of mutating glutamate residues in the amino acid sequence.
Corry
B
B
Protein Dynamics Unit, Department of Chemistry, Australian National University, Canberra, Australian Capital Territory.
Allen
T W
TW
Kuyucak
S
S
Chung
S H
SH
D055592:Biophysical Phenomena; D001703:Biophysics; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004553:Electric Conductivity; D018698:Glutamic Acid / Q000737:chemistry; D017136:Ion Transport; D008564:Membrane Potentials; D008954:Models, Biological; D009154:Mutation; D012964:Sodium / Q000378:metabolism; D055672:Static Electricity; D013816:Thermodynamics
D015220:Calcium Channels; D018698:Glutamic Acid; D012964:Sodium; D002118:Calcium