The neoxanthin binding site of the major light harvesting complex (LHCII) from higher plants.
The localisation of the xanthophyll neoxanthin within the structure of the major light harvesting complex (LHCII) of higher plants has been investigated by site-directed mutagenesis and spectroscopic methods. Mutation analysis performed on pigment binding sites in different helix domains leads to selective loss of neoxanthin for mutations on helix C thus localising this pigment between the helix C and helix A/B domains. Recombinant proteins binding two lutein molecules per polypeptide but lacking neoxanthin have been used in order to determine the contribution of neoxanthin to the absorption and linear dichroism spectra. The data were used to derive the orientation of the neoxanthin transition moment, lying in the polyene chain, which was thus determined to form an angle of 57 +/- 1.5 degrees with respect to the normal to the membrane plane where the protein is inserted. On the basis of these results we propose a model for the localisation of the carotenoid site in the LHCII structure which is still unresolved.
Croce
R
R
Università di Verona, Facoltà di Scienze MM.FF.NN., Biotecnologie Vegetali, Italy.
Remelli
R
R
Varotto
C
C
Breton
J
J
Bassi
R
R
D001665:Binding Sites; D002338:Carotenoids / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D045342:Light-Harvesting Protein Complexes; D014975:Lutein / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods; D024341:Xanthophylls
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011994:Recombinant Proteins; D024341:Xanthophylls; D002734:Chlorophyll; D002338:Carotenoids; C011947:neoxanthin; D014975:Lutein