Biophysical Society Thematic Meeting | Hamburg 2022

Biophysics at the Dawn of Exascale Computers

Poster Abstracts

22-POS Board 22 VOLTAGE SENSING IN PROTEIN-CONDUCTING CHANNEL SECYEG Ferdinand Horvath 1 ; Thomas Renger 1 ; 1 Johannes Kepler University, Department for Theoretical Biophysics, Linz, Austria The bacterial channel SecYEG is responsible for translocating proteins across the plasma membrane. It resides in an energized membrane subjected to the proton motive force (PMF). Experimental reports have shown that the PMF’s electrostatic component allows SecYEG to remain impermeable to ions. When the absolute value of the transmembrane electrostatic potential drops below a certain threshold, however, the channel becomes leaky to ions. The precise mechanism behind this voltage-dependent ion channel activity is still unclear. We employ molecular dynamics simulations to study SecYEG's mechanical response to transmembrane voltages. Although electric fields induce only minute displacements of secondary structure elements within the channel, detailed analysis of intramolecular forces reveals a complex pattern of voltage-dependent stress inside the channel. Using force distribution analysis, we discern voltage-sensitive elements in the channel and highlight networks of interacting residues that constrict the channel pore in the presence of electric fields. We find that, depending on the sign of the transmembrane potential, either helices TM5 and TM7 or TM2 and the plug domain are the most voltage-sensitive elements of the channel.

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