In:
Zeitschrift für Naturforschung C, Walter de Gruyter GmbH, Vol. 35, No. 5-6 ( 1980-6-1), p. 367-375
Abstract:
An extensive study of the chiroptical properties of C-phycoerythrin and the α-and β-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 of mean residue ellipticities and the experimental circular dichroism spectra in the region of the n → π* peptide transition the a-helix contents of the apoproteins of the ac-and ß-subunits are estimated to amount to 60% and 40%, respectively. The circular dichroism spectrum of native C-phycoerythrin is congruent with a linear superposition of the α-and β-subspectra, in the whole spectral region studied. Since a-and β-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°-40°C the thermally induced changes of the chrom ophores in native C-phycoerythrin are not associated with changes of the secondary structure of the apoprotein. Unfolding occurs at 60°-70°C but slowly leads to irreversible denaturation. Protein unfolding starts at 3 M urea. The random coil secondary structure of the apoproteins is reached at 8 M urea. At this concentration the absorbance and the optical activity of 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.
Type of Medium:
Online Resource
ISSN:
1865-7125
,
0939-5075
DOI:
10.1515/znc-1980-5-603
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1980
detail.hit.zdb_id:
2078107-6
SSG:
12
