title: Cytosol has a small effect on protein backbone dynamics.
abstract: Cells are crowded with macromolecules, yet most biophysical information about proteins is obtained in dilute solution. To determine the impact of this dichotomy, we used nuclear magnetic resonance spectroscopy to measure the backbone (15)N T(1) and T(2) relaxation times and the {(1)H}-(15)N nuclear Overhauser enhancement (nOe) of uniformly (15)N-enriched apocytochrome b(5) in living Escherichia coli and in dilute solution. These data allowed us to assess the backbone dynamics of this partially folded protein in cells and in dilute solution. The two data sets were analyzed by using the model-free approach. Transfer from dilute solution to the cytosol has a quantitative effect on T(1), T(2), and nOe values. Most of the effects are attributed to an increase in the overall correlation time, caused by the increased viscosity of the cytosol compared to that of the dilute solution. Our main conclusion is that the cytosol does not alter the pattern of backbone dynamics of apocytochrome b(5). Increases in the time scale of both the picosecond and millisecond motions are observed, but the increases are less than approximately 30%.
authors.affiliation: Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Bryant
authors.forename: Juliette T J
authors.initials: JT
authors.lastname: Lecomte
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Lee
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Young
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Pielak
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D015786:Cytochromes b5 / Q000737:chemistry / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry* / Q000378:metabolism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D011487:Protein Conformation; D017510:Protein Folding; D012996:Solutions / Q000737:chemistry; D013997:Time Factors; D014783:Viscosity
chemical_list: D029968:Escherichia coli Proteins; D012996:Solutions; D015786:Cytochromes b5