| | 1 | Author
| Elisabeth Langer, H. Arald Lehner, Wolfhart Rüdiger, Barbara Zickendraht, -W Endelstadt | Requires cookie* | | | Title
| Circular Dichroism of C-Phycoerythrin: A Conformational Analysis  | | | | Abstract
| An extensive study o f the chiroptical properties o f C-phycoerythrin and the a-and ^-subunits in the spectral region from 700 -200 nm is presented. Based on the VIS-circular dichroism inherently chiral conform ations are proposed for the co valently linked chromophores. By means o f mean residue ellipticities and the experimental circular dichroism spectra in the region o f the n -* n* peptide transition the a-helix contents o f the apoproteins o f the ac-and ß-subunits are estimated to amount to 60% and 40%, respectively. The circular dichroism spectrum o f native C-phycoerythrin is congruent with a linear superposition o f the a-and /?-subspectra, in the whole spectral region studied. Since a-and /?-subunits are associated in native C-phycoery-thrin as revealed by sedim entation analysis the interactions between the subunits in the native chromoprotein are not accom panied by substantial conform ational changes. In the temperature range 0 ° -4 0 °C the thermally induced changes o f the chrom ophores in native C-phycoerythrin are not associated with changes o f the secondary structure o f the apoprotein. Unfolding occurs at 60 0 -7 0 °C but slowly leads to irreversible denaturation. Protein unfolding starts at 3 M urea. The random coil secondary structure o f the apoproteins is reached at 8 M urea. At this concentration the absorbance and the optical activity o f the chrom o phores are reduced by a factor 3 and 10, respectively. The conformational changes in the peptide with increasing denaturant concentration are not synchronous with those induced in the Chromo phore indicating that a m ultistep process is operative during unfolding. The C D results on dena turation are supplem ented by absorption and em ission spectroscopy. | | | |
Reference
| Z. Naturforsch. 35c, 367 (1980); received February 5 1980 | | | |
Published
| 1980 | | | |
Keywords
| Phycoerythrin, Subunits, Conformation o f Chrom ophores and Apoproteins, Circular D ichroism, Denaturation | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0367.pdf | | | | Identifier
| ZNC-1980-35c-0367 | | | | Volume
| 35 | |
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