Structures and functions of carotenoids bound to reaction centers from purple photosynthetic bacteria

Hashimoto, H. et al. (2006) Structures and functions of carotenoids bound to reaction centers from purple photosynthetic bacteria. Pure and Applied Chemistry, 78(8), pp. 1505-1518. (doi: 10.1351/pac200678081505)

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The photoprotective function of 15,15'-cis-carotenoids bound to the photosynthetic reaction centers (RCs) of purple bacteria has been studied using carotenoids reconstituted into carotenoidless RCs from Rhodobacter sphaeroides strain R26.1. The triplet-energy level of the carotenoid has been proposed to affect the quenching of the triplet state of special-pair bacteriochlorophyll (P). This was investigated using microsecond flash photolysis to detect the carotenoid triplets as a function of the number of conjugated double bonds, n. The carotenoid triplet signals were extracted by using singular-value decomposition (SVD) of the huge matrices data, and were confirmed for those having n = 8 to 11. This interpretation assumes that the reconstituted carotenoids occupy the same binding site in the RC. We have been able to confirm this assumption using X-ray crystallography to determine the structures of carotenoidless, wild-type carotenoid-containing, and 3,4-dihydro-spheroidene-reconstituted RCs. The X-ray study also emphasized the importance of the methoxy group of the carotenoids for binding to the RCs. Electroabsorption (Stark) spectroscopy was used to investigate the effect of the carotenoid on the electrostatic field around P. This electrostatic field changed by 10 % in the presence of the carotenoid.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard and Isaacs, Professor Neil and Roszak, Dr Aleksander
Authors: Hashimoto, H., Fujii, R., Yanagi, K., Kusumoto, T., Gardiner, A.T., Cogdell, R.J., Roszak, A.W., Isaacs, N.W., Pendon, Z., Niedzwiedski, D., and Frank, H.A.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
College of Science and Engineering > School of Chemistry
Journal Name:Pure and Applied Chemistry
Journal Abbr.:Pure Appl. Chem.
ISSN (Online):1365-3075
Copyright Holders:Copyright © 2006 International Union of Pure and Applied Chemistry
First Published:First published in Pure and Applied Chemistry 2006 78(8):1505-1518
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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