Oligomeric protein associations: transition from stochastic to deterministic equilibrium

Area of Science:

• Biophysics
• Biochemistry
• Protein dynamics

Background:

• Protein quaternary structure involves subunits associating to form functional complexes.
• Understanding subunit exchange dynamics is crucial for comprehending protein assembly and function.
• Sensitized fluorescence offers a method to monitor molecular interactions in real-time.

Purpose of the Study:

• To investigate subunit exchange mechanisms in protein dimers and tetramers.
• To differentiate between stochastic and deterministic equilibria in protein dissociation.
• To explore the effect of pressure on protein subunit exchange rates.

Main Methods:

• Utilizing sensitized fluorescence to track energy transfer between attached donor and acceptor fluorophores.
• Applying pressure to induce and monitor protein dissociation and subunit exchange.
• Comparing dissociation and association rates in dimers versus tetramers.

Main Results:

• Subunit exchange in dimers occurs at rates comparable to dissociation under pressure.
• Tetramer subunit exchange is significantly slower than dissociation equilibrium attainment.
• Pressure differentially affects dissociation in dimers and association in tetramers.

Conclusions:

• Tetrameric proteins exhibit heterogeneous dissociation properties, behaving like deterministic macroscopic systems.
• Dimeric protein dissociation follows classical stochastic chemical equilibrium principles.
• Protein aggregate behavior can mimic macroscopic mechanical equilibria.