TAILIEUCHUNG - Báo cáo khoa học: Protective effect of active oxygen scavengers on protein degradation and photochemical function in photosystem I submembrane fractions during light stress

The protective role of reactive oxygen scavengers against photodamage was studied in isolated photosystem (PS) I submembrane fractions illumin-ated (2000lEÆm )2 Æs )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 orn-propyl gallate. Chlorophyll photobleaching resulting in a decrease of absorbance and fluorescence, and a blue-shift of both absorbance and fluorescence maxi-mum in the red region, was also greatly delayed in the presence of these scavengers. . | iFEBS Journal Protective effect of active oxygen scavengers on protein degradation and photochemical function in photosystem I submembrane fractions during light stress Subramanyam Rajagopal David Joly Alain Gauthier Marc Beauregard and Robert Carpentier Groupe de Recherche en Biologie Vegetale Universite du Quebec a Trois-Rivières Quebec Canada Keywords photosystem I submembrane fraction active oxygen P700 light stress Correspondence R Carpentier Groupe de Recherche en Biologie Vegetale Universite du Quebec a Trois-Rivieres . 500 Trois-Rivieres Quebec Canada G9A 5H7 Fax 1 819 376 5057 E-mail Robert_Carpentier@ Present address Schoolof Life Sciences and Center for the Study of Early Events in Photosynthesis Arizona State University Tempe Arizona 85287 USA Received 17 August 2004 revised 23 November 2004 accepted 2 December 2004 doi The protective role of reactive oxygen scavengers against photodamage was studied in isolated photosystem PS I submembrane fractions illuminated 2000 iE-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 a-helix content decreased with .

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