Seminar

Conformational Changes in Ion Channels (nerves) and Actomyosin (muscle) Measured by Advanced Fluorescence Methods

Professor Paul R. Selvin
Department of Physics and Biophysics Center
University of Illinois at U-C

Monday, November 29, 1999
4:00 pm
3269 Beckman Institute

Abstract

Fluorescence resonance energy transfer (FRET) is widely used to measure nanometer-scale changes in biomolecules. We have shown that a modification of the technique, which we called lanthanide-based resonance energy transfer (LRET), offers many technical advantages over FRET. We have used LRET to measure conformational changes in voltage-controlled potassium ion channels and in actomyosin. Voltage-controlled ion channels are responsible for nerve impulses and undergo dramatic changes in ion conductivity in response to changes in membrane potential. Electrical measurements have previously established that charged residues in these proteins move in response to voltage but little is known about the magnitude or type (rotation vs translation) of motion. Using LRET, voltage-dependent distance changes were measured within the Shaker Potassium Ion Channel and correlated with simultaneous electrical measurements. These are the first measurements to detect distance changes between residues in a voltage-controlled ion channel, a long-standing goal in the field, and lead to a new model of how the voltage-sensing region moves in response to voltage. Conformational changes in myosin have also been measured. Changes within the myosin head, specifically between the heavy- and light-chain domains, were measured as a function of nucleotide and actin. These results support the notion that conformational changes between these two domains are responsible for the actomyosin powerstroke involved in muscle contraction.

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Tea and coffee will be served in R3151 Beckman Institute at 2:15 pm and you will have this opportunity to meet the speaker.