Title: The principle of gating charge movement in a voltage-dependent K+ channel.

Authors: Youxing Jiang, Vanessa Ruta, Jiayun Chen, Alice Lee, Roderick MacKinnon

Journal, date & volume: Nature, 2003 May 1 , 423, 42-8

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/12721619

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.