Functional role of the beta subunit of high conductance calcium-activated potassium channels.
Mammalian high conductance, calcium-activated potassium (maxi-K) channels are composed of two dissimilar subunits, alpha and beta. We have examined the functional contribution of the beta subunit to the properties of maxi-K channels expressed heterologously in Xenopus oocytes. Channels from oocytes injected with cRNAs encoding both alpha and beta subunits were much more sensitive to activation by voltage and calcium than channels composed of the alpha subunit alone, while expression levels, single-channel conductance, and ionic selectivity appeared unaffected. Channels from oocytes expressing both subunits were sensitive to DHS-I, a potent agonist of native maxi-K channels, whereas channels composed of the alpha subunit alone were insensitive. Thus, alpha and beta subunits together contribute to the functional properties of expressed maxi-K channels. Regulation of co-assembly might contribute to the functional diversity noted among members of this family of potassium channels.
McManus
O B
OB
Department of Membrane Biochemistry and Biophysics, Merck Research Labs, Rahway, New Jersey 07065.
Helms
L M
LM
Pallanck
L
L
Ganetzky
B
B
Swanson
R
R
Leonard
R J
RJ
D000818:Animals; D002118:Calcium / Q000502:physiology*; D005260:Female; D015640:Ion Channel Gating; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology; D009828:Oleanolic Acid / Q000031:analogs & derivatives*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000819:agonists / Q000737:chemistry* / Q000502:physiology*; D018075:RNA, Complementary; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology; D014315:Triterpenes / Q000494:pharmacology; D014982:Xenopus laevis
D046911:Macromolecular Substances; D015221:Potassium Channels; D018075:RNA, Complementary; D012462:Saline Solution, Hypertonic; D012503:Saponins; D014315:Triterpenes; C071764:dehydrosoyasaponin I; D009828:Oleanolic Acid; D002118:Calcium