• Medientyp: E-Artikel
  • Titel: Conformational Changes and Proton Uptake in the Reversible Aggregation of Tobacco‐Mosaic‐Virus Protein
  • Beteiligte: Vogel, Dieter; Jaenicke, Rainer
  • Erschienen: Wiley, 1974
  • Erschienen in: European Journal of Biochemistry
  • Umfang: 607-615
  • Sprache: Englisch
  • DOI: 10.1111/j.1432-1033.1974.tb03303.x
  • ISSN: 1432-1033; 0014-2956
  • Schlagwörter: Biochemistry
  • Zusammenfassung: <jats:p>The coat protein of tobacco mosaic virus is characterized by a complex circular dichroic spectrum in the range of aromatic absorption. Depending on the type of aggregate predominating under specific experimental conditions the various well‐resolved bands show positive or negative changes of their amplitude (Δɛ<jats:sub>λ</jats:sub>≶ 0) which may be correlated quantitatively to corresponding structural transformations. A decrease of the amplitude is observed upon aggregating A‐protein to the double disc, while helix formation leads to a strong increase.</jats:p><jats:p>Starting from the A‐protein at pH 8 (<jats:italic>I</jats:italic>= 0.1, 20°C), double discs may be formed either by decreasing pH or by increasing ionic strength; both methods of aggregation lead to identical changes in dichroic absorption at wavelength 265–290 nm, while at 295 nm only smaller changes occur.</jats:p><jats:p>Following the time dependence of transconformation and aggregation by observing Δɛ<jats:sub>λ</jats:sub> and by component analysis in the ultracentrifuge shows that both processes depend in a critical way on pH, ionic strength and the kind of ions applied. Under certain well‐defined conditions of the solvent the conformational changes precede the aggregation process.</jats:p><jats:p>Correlating the temperature dependence of Δɛ<jats:sub>λ</jats:sub> to that of acidimetric titrations shows a linear relationship between double‐disc formation, proton uptake, and change in dichroic absorption. The proton uptake amounts to 1 proton per monomer built into the double disc (<jats:italic>I</jats:italic>= 0.1).</jats:p><jats:p>Including results from mutant studies of other authors, the wavelength of the different maxima of Δɛ<jats:sub>λ</jats:sub> suggest tyrosine and/or tryptophan residues in the carboxylic end of the polypeptide chain to be involved in the conformational changes upon double‐disc formation.</jats:p>
  • Beschreibung: <jats:p>The coat protein of tobacco mosaic virus is characterized by a complex circular dichroic spectrum in the range of aromatic absorption. Depending on the type of aggregate predominating under specific experimental conditions the various well‐resolved bands show positive or negative changes of their amplitude (Δɛ<jats:sub>λ</jats:sub>≶ 0) which may be correlated quantitatively to corresponding structural transformations. A decrease of the amplitude is observed upon aggregating A‐protein to the double disc, while helix formation leads to a strong increase.</jats:p><jats:p>Starting from the A‐protein at pH 8 (<jats:italic>I</jats:italic>= 0.1, 20°C), double discs may be formed either by decreasing pH or by increasing ionic strength; both methods of aggregation lead to identical changes in dichroic absorption at wavelength 265–290 nm, while at 295 nm only smaller changes occur.</jats:p><jats:p>Following the time dependence of transconformation and aggregation by observing Δɛ<jats:sub>λ</jats:sub> and by component analysis in the ultracentrifuge shows that both processes depend in a critical way on pH, ionic strength and the kind of ions applied. Under certain well‐defined conditions of the solvent the conformational changes precede the aggregation process.</jats:p><jats:p>Correlating the temperature dependence of Δɛ<jats:sub>λ</jats:sub> to that of acidimetric titrations shows a linear relationship between double‐disc formation, proton uptake, and change in dichroic absorption. The proton uptake amounts to 1 proton per monomer built into the double disc (<jats:italic>I</jats:italic>= 0.1).</jats:p><jats:p>Including results from mutant studies of other authors, the wavelength of the different maxima of Δɛ<jats:sub>λ</jats:sub> suggest tyrosine and/or tryptophan residues in the carboxylic end of the polypeptide chain to be involved in the conformational changes upon double‐disc formation.</jats:p>
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