Multiple subunits of a voltage-dependent potassium channel contribute to the binding site for tetraethylammonium.
RNAs encoding a wild-type (RBK1) and a mutant (RBK1(Y379V,V381T); RBK1*) subunit of voltage-dependent potassium channels were injected into Xenopus oocytes. When expressed separately, they made homotetrameric channels that differed about 100-fold in sensitivity to tetraethylammonium (TEA). Mixtures of channels having one, two, or three low affinity subunits were expressed by injecting various proportions of RBK1 and RBK1* RNAs. The affinity for TEA of these three channel species was deduced by fitting concentration-response curves for the inhibition of potassium currents. DNAs were also concatenated to construct a sequence that encoded two connected subunits, and channels that contained four, two, or no TEA-sensitive subunits were expressed. The results suggest that bound TEA interacts simultaneously with all four subunits.
Kavanaugh
M P
MP
Vollum Institute, Oregon Health Sciences University, Portland 97201.
Hurst
R S
RS
Yakel
J
J
Varnum
M D
MD
Adelman
J P
JP
North
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D009865:Oocytes; D015221:Potassium Channels / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013757:Tetraethylammonium Compounds / Q000378:metabolism*; D014982:Xenopus laevis
D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D015221:Potassium Channels; D011994:Recombinant Proteins; D013757:Tetraethylammonium Compounds