Dresden 2017 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 27: Posters - Statistical Physics Biological Systems
DY 27.2: Poster
Dienstag, 21. März 2017, 18:15–21:00, P3
Thermodynamic bounds on the ultra- and infra-affinity of Hsp70 for its substrates — •Basile Nguyen1,2, David Hartich1, Paolo De Los Rios2, and Udo Seifert1 — 1II. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany — 2Laboratory of Statistical Biophysics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Heat shock proteins 70 (Hsp70s) have essential functions in living systems, such as protecting proteins against aggregation and assisting protein folding. They are ATP-driven machines which rely on allosteric regulation to optimally tune their affinity to specific substrates (e.g., misfolded or partially folded proteins). Hsp70s use the chemical free energy from an ATP hydrolysis to show affinity to their substrates beyond the equilibrium bounds, these regimes are called ultra- and infra-affinity. We derive a thermodynamic relation which quantifies how far the affinity can be tuned using the finite energy budget of hydrolysing one ATP. We find that an optimal tuning requires fast hydrolysis and nucleotide exchange reactions with respect to substrate binding and unbinding. Most remarkably, Hsp70s work with cofactors which are observed to catalyze these key reactions. Therefore, we show that the Hsp70 system is optimally tuned to achieve ultra-affinity, thus explaining how it prevents aggregation and refolds efficiently. Finally, we consider small GTPases which can benefit from infra-affinity to optimize intracellular signal transduction.