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Protective effect of active oxygen scavengers on protein degradation and photochemical function in photosystem I submembrane fractions during light stress
Author(s) -
Rajagopal Subramanyam,
Joly David,
Gauthier Alain,
Beauregard Marc,
Carpentier Robert
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2004.04512.x
Subject(s) - chemistry , photochemistry , p700 , histidine , photosystem ii , photosystem , photosystem i , absorbance , photosynthetic reaction centre , circular dichroism , gallate , photoinhibition , reactive oxygen species , biophysics , photosynthesis , stereochemistry , biochemistry , nuclear chemistry , chromatography , electron transfer , biology , amino acid
The protective role of reactive oxygen scavengers against photodamage was studied in isolated photosystem (PS) I submembrane fractions illuminated (2000 µE·m −2 ·s −1 ) for various periods at 4 °C. The photochemical activity of the submembrane fractions measured as P700 photooxidation was significantly protected in the presence of histidine or n‐ propyl gallate. Chlorophyll photobleaching resulting in a decrease of absorbance and fluorescence, and a blue‐shift of both absorbance and fluorescence maximum in the red region, was also greatly delayed in the presence of these scavengers. Western blot analysis revealed the light harvesting antenna complexes of PSI, Lhca2 and Lhca1, were more susceptible to strong light when compared to Lhca3 and Lhca4. The reaction‐center proteins PsaB, PsaC, and PsaE were most sensitive to strong illumination while other polypeptides were less affected. Addition of histidine or n‐ propyl gallate lead to significant protection of reaction‐center proteins as well as Lhca against strong illumination. Circular dichroism (CD) spectra revealed that the α‐helix content decreased with increasing period of light exposure, whereas β‐strands, turns, and unordered structure increased. This unfolding was prevented with the addition of histidine or n‐ propyl gallate even after 10 h of strong illumination. Catalase or superoxide dismutase could not minimize the alteration of PSI photochemical activity and structure due to photodamage. The specific action of histidine and n‐ propyl gallate indicates that 1 O 2 was the main form of reactive oxygen species responsible for strong light‐induced damage in PSI submembrane fractions.