Pressure effects on folded proteins in solution. Hydrogen exchange at elevated pressures

Area of Science:

• Biochemistry
• Chemical Kinetics
• Protein Dynamics

Background:

• Hydrogen exchange is a key reaction for studying protein structure and dynamics.
• Pressure can influence biochemical reactions and protein conformations.

Purpose of the Study:

• To investigate the effect of hydrostatic pressure on base-catalyzed hydrogen exchange in proteins and polypeptides.
• To understand how pressure influences the dynamics of folded proteins versus random coil structures.

Main Methods:

• Measurement of rate constants for hydrogen exchange reactions under varying pressures.
• Calculation of activation volumes (deltaV) from pressure-dependent rate data.

Main Results:

• Observed rate constants for hydrogen exchange increased with pressure in lysozyme and ribonuclease A.
• Activation volumes (deltaV) for folded proteins shifted from positive to negative with increasing pressure.
• Random coil polypeptides (oxidized ribonuclease A, poly(DL-lysine)) showed no significant pressure dependence in their activation volumes.

Conclusions:

• Pressure-induced changes in activation volume suggest solvent penetration or partial unfolding in folded proteins.
• The distinct pressure response highlights differences in structural dynamics between folded proteins and random coils.