min K channels form by assembly of at least 14 subunits.
Injection of min K mRNA into Xenopus oocytes results in expression of slowly activating voltage-dependent potassium channels, distinct from those induced by expression of other cloned potassium channels. The min K protein also differs in structure, containing only a single predicted transmembrane domain. While it has been demonstrated that all other cloned potassium channels form by association of four independent subunits, the number of min K monomers which constitute a functional channel is unknown. In rat min K, replacement of Ser-69 by Ala (S69A) causes a shift in the current-voltage (I-V) relationship to more depolarized potentials; currents are not observed at potentials negative to 0 mV. To determine the subunit stoichiometry of min K channels, wild-type and S69A subunits were coexpressed. Injections of a constant amount of wild-type mRNA with increasing amounts of S69A mRNA led to potassium currents of decreasing amplitude upon voltage commands to -20 mV. Applying a binomial distribution to the reduction of current amplitudes as a function of the different coinjection mixtures yielded a subunit stoichiometry of at least 14 monomers for each functional min K channel. A model is presented for how min K subunits may form a channel.
Tzounopoulos
T
T
Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Guy
H R
HR
Durell
S
S
Adelman
J P
JP
Maylie
J
J
D000818:Animals; D001692:Biological Transport; D004553:Electric Conductivity; D046911:Macromolecular Substances; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D024642:Potassium Channels, Voltage-Gated; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D014981:Xenopus
C484268:Kcne1 protein, rat; D046911:Macromolecular Substances; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011994:Recombinant Proteins; D011188:Potassium