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Small CAB‐like proteins prevent formation of singlet oxygen in the damaged photosystem II complex of the cyanobacterium Synechocystis sp. PCC 6803
Author(s) -
SINHA RAKESH KUMAR,
KOMENDA JOSEF,
KNOPPOVÁ JANA,
SEDLÁŘOVÁ MICHAELA,
POSPÍŠIL PAVEL
Publication year - 2012
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2011.02454.x
Subject(s) - synechocystis , photosystem ii , singlet oxygen , chemistry , photochemistry , thylakoid , biophysics , electron paramagnetic resonance , photosynthesis , spin trapping , photosystem i , photosystem , oxygen , biochemistry , radical , biology , chloroplast , nuclear magnetic resonance , gene , physics , organic chemistry , mutant
ABSTRACT The cyanobacterial small CAB‐like proteins (SCPs) are single‐helix membrane proteins mostly associated with the photosystem II (PSII) complex that accumulate under stress conditions. Their function is still ambiguous although they are assumed to regulate chlorophyll (Chl) biosynthesis and/or to protect PSII against oxidative damage. In this study, the effect of SCPs on the PSII‐specific light‐induced damage and generation of singlet oxygen ( 1 O 2 ) was assessed in the strains of the cyanobacterium Synechocystis sp. PCC 6803 lacking PSI (PSI‐less strain) or lacking PSI together with all SCPs (PSI‐less/ scp ABCDE ‐ strain). The light‐induced oxidative modifications of the PSII D1 protein reflected by a mobility shift of the D1 protein and by generation of a D1‐cytochrome b‐559 adduct were more pronounced in the PSI‐less/ scp ABCDE ‐ strain. This increased protein oxidation correlated with a faster formation of 1 O 2 as detected by the green fluorescence of Singlet Oxygen Sensor Green assessed by a laser confocal scanning microscopy and by electron paramagnetic resonance spin‐trapping technique using 2, 2, 6, 6‐tetramethyl‐4‐piperidone (TEMPD) as a spin trap. In contrast, the formation of hydroxyl radicals was similar in both strains. Our results show that SCPs prevent 1 O 2 formation during PSII damage, most probably by the binding of free Chl released from the damaged PSII complexes.