Equilibrium denaturation studies of mouse beta-nerve growth factor

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Chemistry

Background:

• Mouse beta-nerve growth factor (beta-NGF) is a dimeric protein crucial for neuronal development.
• Understanding the conformational stability and denaturation of beta-NGF is essential for its therapeutic applications.

Purpose of the Study:

• To investigate the equilibrium denaturation of dimeric mouse beta-nerve growth factor (beta-NGF).
• To determine the reversibility of beta-NGF denaturation and the role of disulfide bonds in refolding.
• To quantify the conformational stability of beta-NGF under varying conditions.

Main Methods:

• Spectroscopic techniques including intrinsic fluorescence emission and fluorescence depolarization.
• Circular dichroism (CD) spectroscopy to monitor protein conformation.
• Guanidine hydrochloride and urea as denaturants.
• Nonlinear least-squares fitting to analyze denaturation data and model conformational changes.

Main Results:

• Denaturation by guanidine hydrochloride and urea altered beta-NGF's spectroscopic properties.
• Native-like properties and biological activity were restored upon denaturant removal, indicating reversibility.
• Refolding was dependent on intact disulfide bonds; reduction prevented refolding.
• Denaturation followed a two-state model (N2 = 2D) and was concentration-dependent.
• Conformational stability was determined to be 19.3 +/- 1.1 kcal/mol at pH 7.
• Beta-NGF stability decreased by 25% at pH 4 compared to pH 7.

Conclusions:

• Mouse beta-NGF denaturation is a reversible process.
• The three disulfide bonds are critical for the proper refolding of beta-NGF.
• The conformational stability of beta-NGF is influenced by protein concentration and pH.
• The study provides a quantitative measure of beta-NGF's stability and its dependence on environmental factors.