Evidence for the Involvement of Cyclic Electron Transport in the Protection of Photosystem II against Photoinhibition: Influence of a New Phenolic Compound
详细信息 查看全文
- 作者：Suleyman I. Allakhverdiev ; Vyacheslav V. Klimov ; and Robert Carpentier
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：April 8, 1997
- 年：1997
- 卷：36
- 期：14
- 页码：4149 - 4154
- 全文大小：318K
- 年卷期：v.36,no.14(April 8, 1997)
- ISSN：1520-4995
文摘
Organisms that perform oxygenic photosynthesis are subjected toinhibition of theirphotosynthetic functions when they are exposed to excessiveillumination. Photoinhibition occurs mainlyat the level of photosystem II, where a cyclic electron transport hasoften been proposed to be involvedin photoprotection. However, a demonstration of direct protectionby cyclic photosystem II againstphotoinhibitory damage has been lacking. In this report, we usedthe newly characterized compound4-[methoxybis(trifluoromethyl)methyl]-2,6-dinitrophenylhydrazinemethyl ketone (K-15), known tostimulate cyclic electron transport between the acceptor and donorsides of the photosystem [Klimov, V.V., Zharmukhamedov, S. K., Allakhverdiev, S. I., Kolobanova, L. P., &Baskakov, Y. A. (1993) Biol.Membr. 6, 715-732], to verify if photosystemII is significantly protected by cyclic electron transportagainst aerobic and anaerobic photoinhibitory damage. Thephotoinhibitory quenching of the maximallevel of fluorescence and the decrease of the absorbance change at 685nm related to pheophytinphotoreduction observed during photoinhibitory illumination ofuntreated or Mn-depleted photosystem IIsubmembrane fractions are significantly attenuated in the presence ofK-15. The photodegradation ofcytochrome b559 and the photobleaching of 
-carotene andchlorophyll-670 measured in Mn-depletedphotosystem II preparations are also strongly retarded when K-15 ispresent. The detection, byphotoacoustic spectroscopy, of the energy stored during the cyclicelectron transport is also reported inMn-depleted photosystem II submembrane fractions and in photosystem IIreaction center complexes.This reaction is also gradually photoinhibited due to theprogressive photodegradation of the requiredelectron transport intermediates but is significantly more stable inthe presence of K-15. It is deducedthat cyclic electron transport around photosystem II constitutes aneffective protective mechanism againstphotoinhibitory damage.
-carotene andchlorophyll-670 measured in Mn-depletedphotosystem II preparations are also strongly retarded when K-15 ispresent. The detection, byphotoacoustic spectroscopy, of the energy stored during the cyclicelectron transport is also reported inMn-depleted photosystem II submembrane fractions and in photosystem IIreaction center complexes.This reaction is also gradually photoinhibited due to theprogressive photodegradation of the requiredelectron transport intermediates but is significantly more stable inthe presence of K-15. It is deducedthat cyclic electron transport around photosystem II constitutes aneffective protective mechanism againstphotoinhibitory damage.