Impacts of the charged residues mutation S48E/N62H on the thermostability and unfolding behavior of cold shock protein: insights from molecular dynamics simulation with Gō model

Abstract

The cold shock protein from the hyperthermophile Thermotoga maritima (Tm-Csp) exhibits significantly higher thermostability than its homologue from the thermophile Bacillus caldolyticus (Bc-Csp). Experimental studies have shown that the electrostatic interactions unique to Tm-Csp are responsible for improving its thermostability. In the present work, the favorable charged residues in Tm-Csp were grafted into Bc-Csp by a double point mutation of S48E/N62H, and the impacts of the mutation on the thermostability and unfolding/folding behavior of Bc-Csp were then investigated by using a modified Gō model, in which the electrostatic interactions between charged residues were considered in the model. Our simulation results show that this Tm-Csp-like charged residue mutation can effectively improve the thermostability of Bc-Csp without changing its two-state folding mechanism. Besides that, we also studied the unfolding kinetics and unfolding/folding pathway of the wild-type Bc-Csp and its mutant. It is found that this charged residue mutation obviously enhanced the stability of the C-terminal region of Bc-Csp, which decreases the unfolding rate and changes the unfolding/folding pathway of the protein. Our studies indicate that the thermostability, unfolding kinetics and unfolding/folding pathway of Bc-Csp can be artificially changed by introducing Tm-Csp-like favorable electrostatic interactions into Bc-Csp.

Effects of pH and Salt Concentration on Stability of a Protein G Variant Using Coarse-Grained Models

“…Several levels of approximation have been proposed for protein models and for evaluating the electrostatic contributions of unfolding free energy (10)(11)(12)(13). In several of these studies, versions of structure-based models that include a fixed charge have been adopted to study the contribution of the electrostatic interaction in the unfolded state and the interaction between proteins and charged macromolecules (7,(14)(15)(16)(17)(18).…”