Spectroscopic characterisation of the reaction centre of photosystem II from higher plants

FEBS Letters

van Amerongen, H.¹  Newell, W.R.²  van Grondelle, R.¹  Udvarhelyi, P.³  Aalberts, J.W.¹  Drake, A.F.³  Barber, J.² 

[1] Department of Biophysics, Physics Laboratory of the Free University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands;Department of Pure and Applied Biology, Imperial College of Science and Technology, London SW7 2BB, England;Department of Chemistry, Birkbeck College, 20 Gordon Street London WC1H 0AJ, England

关键词: Reaction center;    Photosystem 11;    Linear dichroism;    Circular dichroism;    Photosynthesis;    Spectroscopy;    PS II;    photosystem II;    RC;    reaction centre;    LD;    linear dichroism;    CD;    circular dichroism;    Chl;    chlorophyll;    BChl;    bacteriochlorophyll;    Cyt;    cytochrome;    BBY;    PS II-enriched membrane fragment;    PAGE;    polyacrylamide gel electrophoresis;   

DOI  :  10.1016/0014-5793(88)80608-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Two different photosystem II particles isolated from pea, a core complex and the D1/D2/Cyt b-559 reaction centre (RC) complex, have been characterised by absorption, linear dichroism (LD) and circular dichroism (CD) spectroscopy. Only one carotenoid contributes to the LD of the reaction centre, in agreement with the biochemical analysis. This carotenoid is oriented parallel to the long axis of the reaction centre. The chlorophyll Q_Y contribution to the LD is oriented perpendicular to the long axis of the reaction centre. The LD of the reaction centre carotenoid is reversed in the core complex. In addition, the contribution of a second carotenoid species can be observed. In the core, the two pools of carotenoid have a rather different orientation with respect to the membrane plane: one parallel, the other perpendicular. In addition, in the core the sign of the LD in the chlorophyll Q_Y region is reversed and red-shifted as compared to the reaction centre. These observations suggest that the reaction centre is oriented with its long axis perpendicular to the long axis of the PS II core and to the membrane plane. The circular dichroism CD of the reaction centre has intense peaks of opposite sign at 444 nm (negative) and 435 nm (positive), which we attribute to exciton coupling between Chl a molecules in the reaction centre. The RC has no CD in the range 460–650 nm; thus there is no exciton coupling between the carotenoid and the other pigments. The lack of CD in this region is consistent with the biochemical analysis of only one carotenoid per reaction centre. The larger core complex exhibits much weaker CD (per Chl). The CD in the Q_Y absorption band indicates exciton coupling between chlorophyll molecules. The sign of the pair of peaks in this region is reversed in the core with respect to the reaction centre.

【 授权许可】

Unknown