Transplantable sites confer calcium sensitivity to BK channels.
Both intracellular calcium and voltage activate Slo1, a high-conductance potassium channel, linking calcium with electrical excitability. Using molecular techniques, we created a calcium-insensitive variant of this channel gated by voltage alone. Calcium sensitivity was restored by adding back small portions of the carboxyl (C)-terminal 'tail' domain. Two separate regions of the tail independently conferred different degrees of calcium sensitivity; together, they restored essentially wild-type calcium dependence. These results suggest that, in the absence of calcium, the Slo1 tail inhibits voltage-dependent gating, and that calcium removes this inhibition. Slo1 may have evolved from an ancestral voltage-sensitive potassium channel represented by the core; the tail may represent the more recent addition of a calcium-dependent modulatory domain.
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology*; D015640:Ion Channel Gating; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D017434:Protein Structure, Tertiary; D014180:Transplantation; D014981:Xenopus