Protein Stiffening and Entropic Stabilization in the Subdenaturing Limit of Guanidine Hydrochloride

Abstract

Subdenaturing concentrations of guanidine hydrochloride (GdnHCl) stabilize proteins. For ferrocytochrome c the stabilization is detected at subglobal level with no measured change in global stability. These deductions are made by comparing observed rates of thermally driven ferrocytochrome cHCO reactions with global unfolding rates of ferrocytochrome c measured by stopped flow and NMR hydrogen exchange in the presence of a wide range of GdnHCl concentrations at pH 7, 22 degrees C.

In vivo detection and quantification of chemicals that enhance protein stability

“…Upon searching the literature, we found that a previous study has shown that the two most common denaturants, urea and guanidinium hydrochloride, can act as protein stabilizers when used in sub-denaturing concentrations [27]. The authors of this study suggest that these denaturants can act as chemical cross-linkers that help establish hydrogen bonds and van der Waal's interactions between main chain and side-chain atoms of proteins leading to limited freedom of motion.…”

“…The authors of this study suggest that these denaturants can act as chemical cross-linkers that help establish hydrogen bonds and van der Waal's interactions between main chain and side-chain atoms of proteins leading to limited freedom of motion. This effect has been termed "protein stiffening" [27].…”

Viscosity-dependent structural fluctuation of the M80-containing Ω-loop of horse ferrocytochrome c

“…The protein chain refolds trapping the CO molecule which is still bonded to the heme iron. Cyt c with the trapped CO (called NCO-state) is structurally native-like [59,60] and it represents a long-lived late kinetic intermediate [61,65,66,67]. Folding is blocked as long as the NCO-state stays frozen in the kinetic trap.…”

“…In this work, we have examined the influence of solvent viscosity on the structural fluctuation of presumably the M80-containing X-loop by measuring the rate of thermally-driven CO-dissociation from the natively folded carbonmonoxycytochrome c (NCO-state). Because of its smaller size and the content of the heme iron, carbonmonoxycytochrome c is a model in experimental protein dynamics studies [41,[57][58][59][60][61][62][63]. The CO-dissociation rate of NCOstate varies inversely with viscosity initially when the solvent viscosity is low (68.0 cP), but saturates at higher viscosity, indicating that the CO-dissociation from the NCO-state involves sequential stages that depend differently on solvent friction, i.e., solvent coupled and nonsolvent-coupled stages of the process [22,47].…”

Equilibrium Unfolding of Neuronal Calcium Sensor-1

“…It has been pointed out previously that even small alterations in backbone dihedral angles are known to change optical activity (27,29,30) due to rigidity or stiffening of protein structure, perhaps locally (31). Protein stiffening is described as likely changes in phi-psi backbone dihedral angles, which comes at the cost of decreasing entropy or spatial freedom (31,32). This may not, however, mean a real change in the secondary structure content (27).…”