ISSN:
1432-2013
Keywords:
Key words Potassium (K) channels
;
Rat eag
;
Activation kinetics
;
Magnesium
;
pH
;
Kinetic model
;
Oocyte expression system
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The rat homologue of Drosophila ether à 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. Extracellular 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050137
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