The alpha subunit of the GTP binding protein activates muscarinic potassium channels of the atrium.
It has been debated whether the potassium channel of the atrium is activated by the alpha subunit or by the beta gamma subunits of guanine nucleotide binding (G) proteins, which dissociate on activation with guanosine triphosphate (GTP). Therefore, the channel-activating effectiveness of these subunits on isolated guinea pig atrial cells was tested. The activated alpha K subunit from human erythrocytes activated the channel in subpicomolar concentrations. The beta gamma dimer from bovine brain activated the channel in nanomolar concentrations. These results support the view that, physiologically, the alpha subunit activates the channel.
Cerbai
E
E
Department of Applied Physiology, University of Cologne, Köln, FRG.
Klöckner
U
U
Isenberg
G
G
D000818:Animals; D016275:Atrial Function; D004553:Electric Conductivity; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D046911:Macromolecular Substances; D011188:Potassium / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*
D007473:Ion Channels; D046911:Macromolecular Substances; D011976:Receptors, Muscarinic; D019204:GTP-Binding Proteins; D011188:Potassium