Transfer of voltage independence from a rat olfactory channel to the Drosophila ether-à-go-go K+ channel.
The S4 segment is an important part of the voltage sensor in voltage-gated ion channels. Cyclic nucleotide-gated channels, which are members of the superfamily of voltage-gated channels, have little inherent sensitivity to voltage despite the presence of an S4 segment. We made chimeras between a voltage-independent rat olfactory channel (rolf) and the voltage-dependent ether-à-go-go K+ channel (eag) to determine the basis of their divergent gating properties. We found that the rolf S4 segment can support a voltage-dependent mechanism of activation in eag, suggesting that rolf has a potentially functional voltage sensor that is silent during gating. In addition, we found that the S3-S4 loop of rolf increases the relative stability of the open conformation of eag, effectively converting eag into a voltage-independent channel. A single charged residue in the loop makes a significant contribution to the relative stabilization of the open stage in eag. Our data suggest that cyclic nucleotide-gated channels such as rolf contain a voltage sensor which, in the physiological voltage range, is stabilized in an activated conformation that is permissive for pore opening.
Tang
C Y
CY
Department of Physiology, School of Medicine, University of California, Los Angeles 90095-1751, USA.
Papazian
D M
DM
D000595:Amino Acid Sequence; D000818:Animals; D001711:Biotransformation / Q000502:physiology; D018076:DNA, Complementary / Q000096:biosynthesis; D004330:Drosophila; D029721:Drosophila Proteins; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012903:Smell / Q000502:physiology*
D018076:DNA, Complementary; D029721:Drosophila Proteins; D051638:Ether-A-Go-Go Potassium Channels; D015221:Potassium Channels; D011993:Recombinant Fusion Proteins; C496883:eag protein, Drosophila