Effect of viscogens on the kinetic response of a photoperturbed allosteric protein

• Published in: The Journal of chemical physics Vol. 141; no. 22; p. 22D514
• Main Authors: Waldauer, Steven A, Stucki-Buchli, Brigitte, Frey, Lukas, Hamm, Peter
• Format: Journal Article
• Language: English
• Published: United States 14-12-2014
• Subjects: Glycerol - chemistry; Humans; Kinetics; Light; Molecular Dynamics Simulation; PDZ Domains; Photochemical Processes; Protein Folding; Protein Tyrosine Phosphatase, Non-Receptor Type 13 - chemistry; Sucrose - chemistry; Viscosity
• ISSN: 1089-7690
• DOI: 10.1063/1.4897975

By covalently binding a photoswitchable linker across the binding groove of the PDZ2 domain, a small conformational change can be photo-initiated that mimics the allosteric transition of the protein. The response of its binding groove is investigated with the help of ultrafast pump-probe IR spectroscopy from picoseconds to tens of microseconds. The temperature dependence of that response is compatible with diffusive dynamics on a rugged energy landscape without any prominent energy barrier. Furthermore, the dependence of the kinetics on the concentration of certain viscogens, sucrose, and glycerol, has been investigated. A pronounced viscosity dependence is observed that can be best fit by a power law, i.e., a fractional viscosity dependence. The change of kinetics when comparing sucrose with glycerol as viscogen, however, provides strong evidence that direct interactions of the viscogen molecule with the protein do play a role as well. This conclusion is supported by accompanying molecular dynamics simulations.