Positive cooperativity in activation of the cardiac muscarinic K+ channel by intracellular GTP
- 1 April 1990
- journal article
- research article
- Published by Springer Nature in Pflügers Archiv - European Journal of Physiology
- Vol. 416 (1-2) , 216-218
- https://doi.org/10.1007/bf00370247
Abstract
Concentration-dependent effects of intracellular GTP on activation of the muscarinic K+ channel were examined in inside-out patches of cardiac atrial myocytes. The pipette solution contained 0.1 μM ACh. GTP (0.01–30 μM) and 0.5 mM MgCl2 were applied to the inside side of the patch membrane. K+ channels were activated with GTP concentration above 0.1 μM. Channel activation reached a maximal value with 1–3 μM GTP. It decreased at GTP concentrations larger than 3 μM, probably due to desensitization. The dependence of the open probability of the channel on intracellular GTP showed a sigmoidal relationship with a Hill coefficient of around 3. A positive cooperative effect of intracellular GTP on the K+ channel may play an important role in amplifying the signal from the membrane receptor to the K+ channel.Keywords
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