Abstract
While opening of cardiac muscarinic K+ channels is mediated by a guanine nucleotide-binding protein, GK, and normally requires both ACh and cytosolic GTP, we demonstrate that in the absence of agonist and G-nucleotides guinea-pig atrial muscarinic K+ channels are activated by cytosolic ATP (K50 = 224 μM). This activation involves a phosphorylating reaction and is most probably related to a transphosphorylation by a nucleoside diphosphate kinase (NDPK) from ATP to GK-bound GDP. This ATP-induced response is completely inhibited by nanomolar concentrations of GDP or GTP, suggesting a G-nucleotide specific binding site on NDPK.
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This wort was supported by a grant of the National Fund for Scientific Research Belgium.
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Heidbüchel, H., Callewaert, G., Vereecke, J. et al. ATP-dependent activation of atrial muscarinic K+ channels in the absence of agonist and G-nucleotides. Pflügers Arch 416, 213–215 (1990). https://doi.org/10.1007/BF00370246
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DOI: https://doi.org/10.1007/BF00370246