Elimination of polarity in the carotenoid terminus promotes the exposure of B850-binding sites (Tyr 44, 45) and ANS-mediated energy transfer in LH2 complexes of Rhodobacter sphaeroides.
Carotenoids in the peripheral light-harvesting complexes (LH2) of the green mutant (GM309) of Rhodobacter sphaeroides were identified as containing neurosporenes, which lack the polar CH(3)O group, compared to spheroidenes in native-LH2 of R. sphaeroides 601. After LH2 complexes were treated with 1-anilino-8-naphthalene sulfonate (ANS), new energy transfer pathways from ANS or tryptophan to carotenoids were discovered in both native- and GM309-LH2. The carotenoid fluorescence intensity of GM309-LH2 was greater than that of native-LH2 when bound with ANS, suggesting that the elimination of polarity in the neurosporene increases the energy transfer from ANS to carotenoid. The fact that two alpha-tyrosines (alpha-Tyr 44, 45, B850-binding sites) in each alpha-apoprotein of GM309-LH2 were more easily modified than those of native-LH2 by N-acetylimidazole (NAI) indicates that the elimination of polarity in the neurosporene terminus increases the exposure of these sites to solution.
Liu
Yuan
Y
Shanghai Institute of Plant Physiology, Shanghai institute for Biological Sciences, Chinese Academy of Science, Shanghai 200032, PR China.
Wu
Yongqiang
Y
Xu
Chunhe
C
D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D001665:Binding Sites; D002338:Carotenoids / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004735:Energy Transfer; D007093:Imidazoles / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D009154:Mutation; D010641:Phenotype; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000378:metabolism*
D000817:Anilino Naphthalenesulfonates; D007093:Imidazoles; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids; D014443:Tyrosine; C027132:1-anilino-8-naphthalenesulfonate; D014364:Tryptophan; C012160:N-acetylimidazole