Functional State Dependence of Picosecond Protein Dynamics

TL;DR

This study investigates how protein dynamics on a picosecond timescale depend on temperature, structure, and function, revealing distinct activation energies linked to structural motions and solvent interactions.

Contribution

It identifies two distinct temperature-dependent processes in protein dynamics and links them to structural motions and solvent interactions, advancing understanding of protein flexibility.

Findings

Native proteins show a double Arrhenius temperature dependence.

Denaturation removes the lower activation energy process.

Ligand binding diminishes the lower activation energy process.

Abstract

We examine temperature dependent picosecond dynamics as a function of structure and function for lysozyme and cytochrome c using temperature dependent terahertz permittivity measurements. A double Arrhenius temperature dependence with activation energies E1 ~ 0.1 kJ/mol and E2 ~10 kJ/mol fits the native state response. The higher activation energy is consistent with the so-called protein dynamical transition associated with beta relaxations at the solvent-protein interface. The lower activation energy is consistent with correlated structural motions. When the structure is removed by denaturing the lower activation energy process is no longer present. Additionally the lower activation energy process is diminished with ligand binding, but not for changes in internal oxidation state. We suggest that the lower energy activation process is associated with collective structural motions that are no longer accessible with denaturing or binding.