Cosolute and Crowding Effects on a Side-By-Side Protein Dimer.

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• Protein stability is influenced by cosolutes, with volume effects stabilizing and chemical interactions having varied effects.
• Proteins typically function in complex cellular environments, not in isolation.

Purpose of the Study:

• To investigate the impact of small and large cosolutes on the stability of a simple protein-dimer interface.
• To understand the role of chemical interactions in protein-protein interactions under crowded conditions.

Main Methods:

• Utilized 19F nuclear magnetic resonance (NMR) spectroscopy to measure the dimer dissociation constant.
• Tested a range of cosolutes, including urea, trimethylamine N-oxide (TMAO), Ficoll, and biologically relevant macromolecules.

Main Results:

• Observed that chemical interactions between cosolutes and the test protein mirrored those affecting monomeric protein stability.
• Demonstrated that physiologically relevant cosolutes like bovine serum albumin and lysozyme also exert significant chemical influences.
• Reconstituted E. coli cytosol confirmed the importance of these interactions in a complex mixture.

Conclusions:

• Chemical interactions are a key determinant of protein-protein interaction stability in the presence of cosolutes.
• Findings provide a foundation for understanding macromolecular crowding effects on protein complex formation and function.