Investigating protein unfolding kinetics by pulse proteolysis

Area of Science:

• Biochemistry
• Biophysics
• Protein Science

Background:

• Studying protein unfolding kinetics in crude samples is challenging but offers opportunities to explore protein energetics.
• Existing methods often require protein purification, limiting their applicability.
• A facile method is needed to investigate protein unfolding in complex biological mixtures.

Purpose of the Study:

• To develop and validate "pulse proteolysis" as a method for determining protein unfolding kinetics in crude samples.
• To assess the accuracy of pulse proteolysis by comparing results with established techniques.
• To investigate the influence of ligand binding on protein unfolding kinetics.

Main Methods:

• Employed "pulse proteolysis" to probe protein unfolding kinetics by differentiating susceptibility between folded and unfolded states.
• Utilized electrophoretic separation to monitor protein unfolding without prior purification.
• Applied the method to E. coli maltose binding protein (MBP) and E. coli ribonuclease H (RNase H).

Main Results:

• Unfolding kinetic constants obtained via pulse proteolysis closely matched those determined by circular dichroism.
• Successfully determined unfolding kinetics for overexpressed MBP in unpurified cell lysate.
• Quantified the dissociation equilibrium constant (K(d)) for the MBP-maltose complex using unfolding kinetic data.

Conclusions:

• Pulse proteolysis is a feasible and accurate quantitative tool for investigating protein unfolding kinetics.
• The method allows for the study of protein energetics in crude samples, including ligand binding effects.
• This technique simplifies the analysis of protein stability and dynamics in complex biological systems.