Single molecule force spectroscopy reveals the temperature-dependent robustness and malleability of a hyperthermophilic protein

Abstract

The ability of thermophilic and hyperthermophilic proteins to maintain their native structure, yet be dynamic and flexible is a key determinant of their ability to function at the extremes of environmental temperatures found on Earth. An understanding of the design principles governing their material properties is important in the development of biomaterials which are able to withstand such extreme conditions. Single molecule force spectroscopy is used to characterise the mechanical flexibility of cold shock protein B from a hyperthermophilic organism, Thermotoga maritima, in the temperature range from 5–40 °C. We measure temperature-dependent changes in features of the unfolding energy landscape of this protein by studying the pulling speed dependence of the unfolding force with temperature in combination with Monte Carlo simulations. We find that the position of the transition state to unfolding shifts away from the native state with increased temperature, reflecting a reduction in the spring constant of the protein and an increase in the malleability of the structure. The mechanical robustness and malleability of this cold shock protein over the temperature range studied, provides an insight into the dynamical properties of hyperthermophilic proteins and lays the foundations for further studies using this highly structurally conserved protein family.