Probing the pigment binding sites in LHCII with resonance Raman spectroscopy: The effect of mutations at S123.
Resonance Raman spectroscopy was used to evaluate the structure of light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCII), reconstituted from wild-type (WT) and mutant apoproteins over-expressed in Escherichia coli. The point mutations involved residue S123, exchanged for either P (S123P) or G (S123G). In all reconstituted proteins, lutein 2 displayed a distorted conformation, as it does in purified LHCII trimers. Reconstituted WT and S123G also exhibited a conformation of bound neoxanthin (Nx) molecules identical to the native protein, while the S123P mutation was found to induce a change in Nx conformation. This structural change of neoxanthin is accompanied by a blue shift of the absorption of this carotenoid molecule. The interactions assumed by (and thus the structure of the binding sites of) the bound Chls b were found identical in all the reconstituted proteins, and only marginally perturbed as compared to purified LHCII. The interactions assumed by bound Chls a were also identical in purified LHCII and the reconstituted WT. However, the keto carbonyl group of one Chl a, originally free-from-interactions in WT LHCII, becomes involved in a strong H-bond with its environment in LHCII reconstituted from the S123P apoprotein. As the absorption in the Qy region of this protein is identical to that of the LHCII reconstituted from the WT apoprotein, we conclude that the interaction state of the keto carbonyl of Chl a does not play a significant role in tuning the binding site energy of these molecules.
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198 Gif-sur-Yvette cedex, France.
Elizabeth
E
Kish
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
Ke
K
Wang
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198 Gif-sur-Yvette cedex, France.
Manuel J
MJ
Llansola-Portoles
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198 Gif-sur-Yvette cedex, France.
Cristian
C
Ilioaia
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198 Gif-sur-Yvette cedex, France.
Andrew A
AA
Pascal
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198 Gif-sur-Yvette cedex, France.
Bruno
B
Robert
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
Chunhong
C
Yang
D001665:Binding Sites; D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D014975:Lutein / Q000737:chemistry; D009154:Mutation; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D024341:Xanthophylls / Q000737:chemistry
D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D002734:Chlorophyll; C037184:chlorophyll b; C011947:neoxanthin; D014975:Lutein; D000077194:Chlorophyll A
Carotenoid; Electronic absorption; LHCII; Lutein; Neoxanthin; Resonance Raman