Assignment of spectral substructures to pigment-binding sites in higher plant light-harvesting complex LHC-II.
The trimeric main light-harvesting complex (LHC-II) is the only antenna complex of higher plants of which a high-resolution 3D structure has been obtained (Kühlbrandt, W., Wang, D., and Fujiyoshi, Y. (1994) Nature 367, 614-621) and which can be refolded in vitro from its components. Four different recombinant forms of LHC-II, each with a specific chlorophyll (Chl) binding site removed by site-directed mutagenesis, were refolded from heterologously overexpressed apoprotein, purified pigments, and lipid. Absorption spectra of mutant LHC-II were measured in the temperature range from 4 to 300 K and compared to likewise refolded wild-type complex and to native LHC-II isolated from pea chloroplasts. Chls at different binding sites have characteristic, well-defined absorption sub-bands. Mixed occupation of binding sites with Chls a and b is not observed. Temperature-dependent changes of the mutant absorption spectra reveal a consistent shift of the major difference bands but an irregular behavior of minor bands. A model of the spectral substructure of LHC-II is proposed which accounts for the different absorption properties of the 12 individual Chls in the complex, thus establishing a first consistent correlation between the 3D structure of LHC-II and its spectral properties. The spectral substructure is valid for recombinant and native LHC-II, indicating that both have the same spatial arrangement of Chls and that the refolded complex is fully functional.
Rogl
Hans
H
Max-Planck-Institut für Biophysik, Heinrich-Hoffmann-Str. 7, D-60528 Frankfurt/Main, Germany. rogl@ciml.univ-mrs.fr
Schödel
Rene
R
Lokstein
Heiko
H
Kühlbrandt
Werner
W
Schubert
Axel
A
D001665:Binding Sites / Q000235:genetics; D002338:Carotenoids / Q000737:chemistry / Q000235:genetics; D002734:Chlorophyll / Q000737:chemistry* / Q000235:genetics; D000077194:Chlorophyll A; D005615:Freezing; D045342:Light-Harvesting Protein Complexes; D016297:Mutagenesis, Site-Directed; D018532:Pisum sativum; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D018724:Spinacia oleracea
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; D002338:Carotenoids; C037184:chlorophyll b; D000077194:Chlorophyll A