2Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia; fax: +7 (496) 733-0532; E-mail: firstname.lastname@example.org
3Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, 117977 Moscow, Russia; fax: +7 (495) 651-2191; E-mail: email@example.com
* To whom correspondence should be addressed.
Received July 14, 2014; Revision received September 2, 2014
The pigment–protein complex of photosystem 2 (PS 2) catalyzes the light-driven oxidation of water molecule and the reduction of plastoquinone. In this work, we studied the effect of the disaccharide trehalose, which is unique in its physicochemical properties, on isolated PS 2 complex. It was found that trehalose significantly stimulated the steady-state rate of oxygen evolution. The study of single flash-induced fluorescence decay kinetics demonstrated that trehalose did not affect the rate of QA– oxidation, although it led to an increase in the relative fractions of PS 2 reaction centers capable of QA– oxidation. Trehalose also prevented PS 2 complexes from being inactivated on prolonged storage. We propose that in the presence of trehalose, which affects the extent of hydration, the protein can preferentially exist in a more optimal conformation for effective functioning.
KEY WORDS: photosystem 2, water-oxidizing complex, oxygen evolution, trehalose, chlorophyll fluorescence, plastoquinone oxidation