Regulation of adenylyl cyclase from Paramecium by an intrinsic potassium conductance.
Hyperpolarization of the cell membrane of Paramecium stimulates adenosine 3',5'-monophosphate (cAMP) formation. Manipulations of the K+ resting conductance of the ciliate by adaptation in different buffers affected excitability of the cAMP generating system. Blockade of K+ channels inhibited hyperpolarization-stimulated cAMP formation. A mutant of Paramecium that is unable to control its K+ resting conductance had a defect in cAMP formation. Purified adenylyl cyclase, when incorporated into an artificial lipid bilayer membrane, revealed properties of a voltage-independent K+ channel. This indicates that the adenylyl cyclase of Paramecium has a secondary function as carrier of the K+ resting conductance. A hyperpolarization-activated K+ efflux appears to directly regulate adenylyl cyclase activity in vivo.
Pharmazeutisches Institut, Universität Tübingen, Germany.
J E
JE
Schultz
S
S
Klumpp
R
R
Benz
W J
WJ
Schürhoff-Goeters
A
A
Schmid
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002923:Cilia / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism; D006706:Homeostasis; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D010247:Paramecium / Q000201:enzymology / Q000502:physiology*; D011188:Potassium / Q000502:physiology*
D007473:Ion Channels; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D011188:Potassium