The N-terminus of the K channel KAT1 controls its voltage-dependent gating by altering the membrane electric field.
Functional roles of different domains (pore region, S4 segment, N-terminus) of the KAT1 potassium channel in its voltage-dependent gating were electrophysiologically studied in Xenopus oocytes. The KAT1 properties did not depend on the extracellular K+ concentration or on residue H267, equivalent to one of the residues known to be important in C-type inactivation in Shaker channels, indicating that the hyperpolarization-induced KAT1 inward currents are related to the channel activation rather than to recovery from inactivation. Neutralization of a positively charged amino acid in the S4 domain (R176S) reduced the gating charge movement, suggesting that it acts as a voltage-sensing residue in KAT1. N-terminal deletions alone (e.g., delta20-34) did not affect the gating charge movement. However, the deletions paradoxically increased the voltage sensitivity of the R176S mutant channel, but not that of the wild-type channel. We propose a simple model in which the N-terminus determines the KAT1 voltage sensitivity by contributing to the electric field sensed by the voltage sensor.
Marten
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Department of Physiology and Biophysics, College of Medicine, The University of Iowa, Iowa City 52242, USA.
Hoshi
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T
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D005260:Female; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016254:Mutagenesis, Insertional; D009865:Oocytes / Q000502:physiology*; D010940:Plant Proteins; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000096:biosynthesis / Q000737:chemistry* / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D017384:Sequence Deletion; D013997:Time Factors; D014982:Xenopus laevis
D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011994:Recombinant Proteins; D011188:Potassium