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Common crowding agents have only a small effect on protein-protein interactions
Yael Phillip1, Eilon Sherman, Gilad Haran
1Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Biophysical Journal
|August 5, 2009
Summary
Cellular crowding has minimal impact on specific protein-protein dimerization. Researchers found that crowding agents did not significantly alter binding affinities for key protein pairs, suggesting in vivo interactions may resemble dilute solutions.
Area of Science:
- Biochemistry and Molecular Biology
- Cellular Biophysics
Background:
- Intracellular environments are crowded with macromolecules, influencing biomolecular interactions.
- Previous studies indicated macromolecular crowding enhances oligomerization and polymerization.
- The effect of crowding on specific protein complex association rates was less understood.
Purpose of the Study:
- To investigate the equilibrium effects of macromolecular crowding on protein heterodimerization.
- To compare crowding effects on strong binding pairs (TEM1-beta-lactamase/BLIP, barnase/barstar) and a weak pair (CyPet-YPet).
- To determine how crowding influences association rates, dissociation rates, affinities, and thermodynamic parameters.
Main Methods:
- Studied protein heterodimerization in solutions containing crowding agents like polyethylene glycol (PEG) and dextran.
- Measured association and dissociation rate constants for protein-protein interactions.
- Determined binding affinities and thermodynamic parameters using biophysical techniques.
Main Results:
- Crowding agents had a minor effect on the association and dissociation rates of TEM1-beta-lactamase/BLIP and barnase/barstar.
- Binding affinities for these strong interacting pairs remained similar to those in dilute aqueous solutions.
- The weak binding pair CyPet-YPet exhibited aggregation rather than enhanced dimerization in PEG solutions.
Conclusions:
- Macromolecular crowding agents exert minimal influence on specific protein-protein dimerization reactions.
- The observed effects on binding kinetics and affinity are largely independent of crowding conditions.
- In vivo protein binding may not significantly differ from measurements in dilute solutions, despite cellular crowding.
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