Luminescence Resonance Energy Transfer Studies of the Shaker Potassium Voltage-Gated Ion Channel

"Members of the superfamily of voltage-gated ion channels are the molecular components underlying electrical excitability in nerves and muscle. Voltage-gated channels allow the selective flow of ions across the hydrophobic lipid bilayer of a cell, opening and closing in response to changes in the voltage across the membrane. The Shaker K+ channel is a standard model system for studying the structure-function relationships in this important class of ion channels. Voltage sensing is known to involve a highly charged segment of the channel called S4. When a channel opens it moves some of these S4 charges across the membrane electric field. The movement of four S4s, one from each identical subunit of Shaker, is coupled to the ""gate"" which opens and closes the pore. Therefore, a central question for understanding the functionality of these proteins is; how exactly does S4 move? Recently, the first crystal structure for a voltage-gated K+ channel was solved. This structure, of the KvAP channel, led the authors to propose a new model of S4 movement. This new model, called the paddle model, hypothesized a large translational motion of S4 across most of the lipid bilayer thickness, a view that has been very controversial. In this study, we examine the conformational movements associated with the S4 segment during voltage sensing. We use a technique called Lanthanide Resonance Energy Transfer (LRET), which gives an accurate distance measurement between two positions on the ion channel. We use two different configurations for LRET on Shaker. The first measures distances between the four identical S4 amino-acid sites on the homotetrameric K+ channel. The second measures distances between S4 sites and a scorpion toxin bound to the symmetric axis of the channel just above the pore. These LRET studies argue strongly against the paddle model of voltage sensing, and demonstrate that the physical movements of the S4 segments of Shaker K+ channels are quite small."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Posson, David John

Contributors dc:contributor

• Selvin, Paul R.

• Biophysics, General

Language dc:language

eng

Identifier

(MiAaPQ)AAI3182357

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/80513