Condensed Matter Physics Seminar

Thursday, May 11, 2000, 2 p.m.
Plant Sciences Building, Room 1130

Gating of membrane channels by voltage and stretch

Marco Colombini and Sergei Sukharev

(Department of Biology, University of Maryland)

Abstract:  The goal of this seminar is to present two ongoing biophysical projects to physicists on this campus. We describe two proteins that form water-filled pores called channels in lipid membranes. Their general function is the establishment of specific types of communication between membrane-separated compartments in the cell.  One channel (called VDAC) is a protein found in mitochondrial membranes.  Voltages in the 10 to 30 mV range induce reversible structural changes resulting in drastic changes in pore diameter and ion selectivity.  This voltage-gating can be amplified or diminished.  Evidence will be presented for the molecular basis for ion selectivity, voltage-sensing, and the structural changes responsible for the changes in function.   Another channel,  the Large-conductance mechanosensitive channel (called MscL), opens a 3 nm pore when the tension in the membrane reaches approximately 10  dynes/cm.  Kinetic analysis of gating transitions predicts the presence of elastic elements in the channel structure. Based on the crystal structure of the closed conformation of the protein, we propose the sequence of molecular events that leads to the channel opening.  Questions of general physical interest pertaining to these systems will be discussed.

Host: Victor Yakovenko

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