Osmolyte effects on protein stability and solubility: a balancing act between backbone and side-chains

Area of Science:

• Biochemistry
• Molecular Biology
• Thermodynamics

Background:

• Intracellular osmolyte molecules, often present at molar concentrations, play crucial roles in cellular adaptation.
• Their influence on protein thermodynamics and stability remains an area of active investigation.

Purpose of the Study:

• To develop and validate a predictive model for the effect of osmolytes on protein stability.
• To understand how osmolytes modulate the native (N) and denatured (D) states of proteins.

Main Methods:

• Utilizing atomic coordinates to calculate the transfer free energy of a native protein (ΔG(tr,N)) by summing component parts.
• Employing a self-avoiding random coil model to predict the transfer free energy of the denatured state (ΔG(tr,D)).
• Calculating the m-value (osmolyte effect on N⇌D transition) as the difference between predicted ΔG(tr,D) and ΔG(tr,N).

Main Results:

• Demonstrated a 1:1 correspondence between predicted and measured m-values for 46 proteins and 9 osmolytes.
• The model accurately predicted protein stability changes across a range of 12 kcal/mol/M.
• Identified varying effects of osmolytes on protein solubility and stability.

Conclusions:

• The developed model provides a robust method for predicting osmolyte effects on protein thermodynamics.
• Understanding these effects is key to elucidating the biological roles of osmolytes in adaptation.
• Osmolytes exhibit diverse interactions with protein components, influencing protein stability and solubility.