The rat homologue of Drosophila ether a gogo cDNA (rat eag) encodes voltage-activated potassium (K) channels with distinct activation properties. Using the Xenopus expression system, we examined the importance of extracellular Mg2+ on the activation of rat eag. ExtracelIular Mg2+ at physiological concentrations dramatically slowed the activation in a dose- and voltage-dependent manner. Other divalent cations exerted similar effects on the activation kinetics that correlated with their enthalpy of hydration. Lowering the external pH also resulted in a slowing of the activation. Protons competed with Mg2+ as the effect of Mg2+ was abolished at low pH. A kinetic model for rat eag activation was derived from the data indicating that all four channel subunits undergo a Mg2+-dependent conformational transition prior to final channel activation. The strong dependence of rat eag activation on both the resting potential and the extracellular Mg2+ concentration constitutes a system for fine-tuning K channel availability in neuronal cells.
CITATION STYLE
Terlau, H., Ludwig, J., Steffan, R., Pongs, O., Stühmer, W., & Heinemann, S. H. (1996). Extracellular Mg2+ regulates activation of rat eag potassium channel. Pflugers Archiv European Journal of Physiology, 432(2), 301–312. https://doi.org/10.1007/s004240050137
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