title: Cosolute and Crowding Effects on a Side-By-Side Protein Dimer.
abstract: The effects of small (∼102Da) and larger (>103Da) cosolutes on the equilibrium stability of monomeric globular proteins are broadly understood, excluding volume stabilizes proteins and chemical interactions are stabilizing when repulsive, but destabilizing when attractive. Proteins, however, rarely work alone. Here, we investigate the effects of small and large cosolutes on the equilibrium stability of the simplest defined protein-protein interactions, the side-by-side homodimer formed by the A34F variant of the 56-residue B1 domain of protein G. We used19F nuclear magnetic resonance spectroscopy to quantify the effects of urea, trimethylamine oxide, Ficoll, and more physiologically relevant cosolutes on the dimer dissociation constant. The data reveal the same stabilizing and destabilizing influences from chemical interactions as observed in studies of protein stability. Results with more physiologically relevant molecules such as bovine serum albumin, lysozyme, and reconstituted Escherichia coli cytosol reflect the importance of chemical interactions between these cosolutes and the test protein. Our study serves as a stepping-stone to a more complete understanding of crowding effects on protein-protein interactions.
authors.affiliation: Department of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Guseman
authors.affiliation: Department of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Gary J
authors.identifier: 0000-0001-6307-542X
authors.initials: GJ
authors.lastname: Pielak
mesh_terms: D003600:Cytosol / Q000737:chemistry; D004926:Escherichia coli / Q000166:cytology; D005362:Ficoll / Q000737:chemistry; D005461:Fluorine; D008744:Methylamines / Q000737:chemistry; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D055503:Protein Multimerization; D055550:Protein Stability; D018080:Receptors, GABA-B / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D014508:Urea / Q000737:chemistry
chemical_list: D008744:Methylamines; D018080:Receptors, GABA-B; D005362:Ficoll; D012710:Serum Albumin, Bovine; D005461:Fluorine; D014508:Urea; D009113:Muramidase; C005855:trimethyloxamine