Translational and rotational diffusion of a small globular protein under crowded conditions.
Protein-protein interaction is the fundamental step of biological signal transduction. Interacting proteins find each other by diffusion. To gain insight into diffusion under the crowded conditions found in cells, we used nuclear magnetic resonance spectroscopy (NMR) to measure the effects of solvent additives on the translational and rotational diffusion of the 7.4 kDa globular protein, chymotrypsin inhibitor 2. The additives were glycerol and the macromolecular crowding agent, polyvinyl pyrrolidone (PVP). Both translational diffusion and rotational diffusion decrease with increasing solution viscosity. For glycerol, the decrease obeys the Stokes-Einstein and Stokes-Einstein Debye laws. Three types of deviation are observed for PVP: the decrease in diffusion with increased viscosity is less than predicted, this negative deviation is greater for rotational diffusion, and the negative deviation increases with increasing PVP molecular weight. We discuss our results in terms of other studies on the effects of macromolecules on globular protein diffusion.
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, USA.
Conggang
C
Li
Yaqiang
Y
Wang
Gary J
GJ
Pielak
D004058:Diffusion; D005990:Glycerol / Q000737:chemistry; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry; D011759:Pyrrolidines / Q000737:chemistry; D012399:Rotation; D015398:Signal Transduction; D012997:Solvents / Q000737:chemistry; D014783:Viscosity
D010455:Peptides; D010940:Plant Proteins; D011145:Polyvinyls; D011759:Pyrrolidines; D012997:Solvents; C093336:chymotrypsin inhibitor 2; C505150:poly(N-vinylpyrrolidine); D005990:Glycerol