1. Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
2. Present address: University of Texas Southwestern Medical Center, Department of Physiology, 5323 Harry Hines Blvd, Dallas, Texas 75390-9040, USA.

Correspondence to: Roderick MacKinnon Correspondence and requests for materials should be addressed to R.M. (Email: mackinn@rockvax.rockefeller.edu).

Abstract

The steep dependence of channel opening on membrane voltage allows voltage-dependent K⁺ channels to turn on almost like a switch. Opening is driven by the movement of gating charges that originate from arginine residues on helical S4 segments of the protein. Each S4 segment forms half of a 'voltage-sensor paddle' on the channel's outer perimeter. Here we show that the voltage-sensor paddles are positioned inside the membrane, near the intracellular surface, when the channel is closed, and that the paddles move a large distance across the membrane from inside to outside when the channel opens. KvAP channels were reconstituted into planar lipid membranes and studied using monoclonal Fab fragments, a voltage-sensor toxin, and avidin binding to tethered biotin. Our findings lead us to conclude that the voltage-sensor paddles operate somewhat like hydrophobic cations attached to levers, enabling the membrane electric field to open and close the pore.

1. Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
2. Present address: University of Texas Southwestern Medical Center, Department of Physiology, 5323 Harry Hines Blvd, Dallas, Texas 75390-9040, USA.

Correspondence to: Roderick MacKinnon Correspondence and requests for materials should be addressed to R.M. (Email: mackinn@rockvax.rockefeller.edu).