PARENT SESSION
Posters P8A Cytochrome b-c complexes. Abstracts (382-393)

Spectral analysis on the structure and function of carotenoid in the cytochrome b₆f complex from marine green alga Bryopsis corticulans. Liang-bi Li^*,1, Bin-xing Li², Yu-Long Liu³, Ting-yun Kuang⁴, ¹ 20 Nanxincun, Xiangshan, Haidian District, Institute of Botany,The Chinese Academy of Sciences, Beijing 100093, China, China² 20 Nanxincun, Xiangshan, Haidian District, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China, China³ Institute of Physics, the Chinese Academy of Sciences, Beijing 100080, China, China⁴ 20 Nanxincun, Xiangshan, Haidian District, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China, China

ABSTRACT- The cytochrome b6f complex(Cytb6f) was isolated and purified from the chloroplasts of marine green alga Bryopsis corticulans by an improved method. The pure Cytb6f preparation was composed of four major subunits, Cytf(34.8kDa), Cytb6(24.0 kDa), Rieske [Fe-S]-protein (18.7kDa) and subunit IV(16.7kDa). Cytb6/f ratio of the preparation was approximately 2.0. After the Cytb6f preparation was reconstituted with lipids isolated from thylakoid membrane of spinach, its electron transfer activity (C10-PQH2-PC) was 73 electron per second. In this work, the molecular configuration and function of carotenoid in the Cytb6f preparation were investigated by HPLC, Absorption, CD, Resonance Raman Spectroscopy and Fluorescence Excitation Spectra. The experimantal results as follows were obtained: 1) The purified Cytb6f complex contains about 1.2 chlorophylla (Chla) and 0.8 carotenoid molecule pur cytf; 2) The carotenoid in the cytb6f complex is part of a-carotene molecule (a-Car) taking a 9-cis configuration and remains in an asymmetric protein environment; 3) The light energy absorbed by this 9-cis-a-Car can efficiently transfer to Chla in the cytb6f complex, and the protective function of the 9-cis-a-Car to photodamage of Chla induced by the strong light is more pronounced.

KEY WORDS: Marine green alga, Cytochrome b6f complex, a-Carotene