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

• Published in: Biochemical and biophysical research communications Vol. 325; no. 2; pp. 600 - 604
• Main Authors: Liu, Yuan, Wu, Yongqiang, Xu, Chunhe
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 10.12.2004
• Subjects: Anilino Naphthalenesulfonates - chemistry; Binding Sites; Carotenoid; Carotenoids - chemistry; Carotenoids - genetics; Carotenoids - metabolism; Chemical modification; Chromatography, High Pressure Liquid - methods; Energy Transfer; Imidazoles - chemistry; Light-harvesting complexes; Light-Harvesting Protein Complexes - chemistry; Light-Harvesting Protein Complexes - metabolism; Mass Spectrometry - methods; Mutation; Phenotype; Photosynthesis; Rhodobacter sphaeroides; Rhodobacter sphaeroides - metabolism; Spectrometry, Fluorescence; Tryptophan - chemistry; Tyrosine - metabolism; Chemical modification; Light-harvesting complexes; Photosynthesis; Carotenoid
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2004.10.067

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 3O 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 α-tyrosines (α-Tyr 44, 45, B850-binding sites) in each α-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.