The N-terminus of the K channel KAT1 controls its voltage-dependent gating by altering the membrane electric field

Biophys J. 1998 Jun;74(6):2953-62. doi: 10.1016/S0006-3495(98)78002-6.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Membrane / physiology
  • Female
  • Kinetics
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mutagenesis, Insertional
  • Oocytes / physiology*
  • Plant Proteins
  • Point Mutation
  • Polymerase Chain Reaction
  • Potassium / pharmacology
  • Potassium Channels / biosynthesis
  • Potassium Channels / chemistry*
  • Potassium Channels / physiology*
  • Potassium Channels, Inwardly Rectifying*
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Sequence Deletion
  • Time Factors
  • Xenopus laevis

Substances

  • Plant Proteins
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • Recombinant Proteins
  • Potassium