Jessica Swanson (University of Utah): Multiscale kinetic modeling reveals fundamental differences between electrically driven and chemically driven ion exchange

Speaker: Jessica Swanson, University of Utah

Host: Pratyush Tiwary

Abstract: 

Electrochemical gradients, such as the proton motive force, play a central role in bioenergetic transformations. Although they are the consequence of one thing—a transmembrane solute gradient—they pack a double punch of energetic driving forces: one due to the dissipative force of a solute moving down its concentration gradient, and the other due to the electrostatic force of charged species moving in response to an electric field.  These two forces are commonly assumed to have an equivalent impact on ion transport due to their Nernstian relationship. 

In this work, we challenge this notion, highlighting differences in both the physical influence of the two forces on the transport reaction free energy landscape as well as on the reaction flux through competing reaction pathways.  Using multiscale kinetic modeling we quantify the influences of both driving forces in the reaction network for coupled Cl–/H+ exchange in ClC antiporters.  This allows us to describe for the first time the competing experimental assays for pH-dependent ion flux.  Comparing these results to simple model systems reveals a critical role of the lower ion binding site, which has been heavily debated.  This work suggests the potential role of ClC-ec1 in bacterial extreme acid response and has broad implications for electrochemically driven transmembrane mechanisms.

Seminars start at 4:00 pm, and refreshments will be served at 3:45 pm. All seminars are held in the Conference Room (1116) of the Institute for Physical Science and Technology (IPST) Building unless otherwise noted.