Biophys J, June 1998, p. 2953-2962, Vol. 74, No. 6

The N-Terminus of the K Channel KAT1 Controls Its Voltage-Dependent Gating by Altering the Membrane Electric Field

Department of Physiology and Biophysics, College of Medicine, The University of Iowa, Iowa City, Iowa 52242 USA

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., 20-34) 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.

Biophys J, June 1998, p. 2953-2962, Vol. 74, No. 6
© 1998 by the Biophysical Society   0006-3495/98/06/2953/10  $2.00

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