title: Protection by α-tocopherol of the repair of photosystem II during photoinhibition in Synechocystis sp. PCC 6803.
abstract: α-Tocopherol is a lipophilic antioxidant that is an efficient scavenger of singlet oxygen. We investigated the role of α-tocopherol in the protection of photosystem II (PSII) from photoinhibition using a mutant of the cyanobacterium Synechocystis sp. PCC 6803 that is deficient in the biosynthesis of α-tocopherol. The activity of PSII in mutant cells was more sensitive to inactivation by strong light than that in wild-type cells, indicating that lack of α-tocopherol enhances the extent of photoinhibition. However, the rate of photodamage to PSII, as measured in the presence of chloramphenicol, which blocks the repair of PSII, did not differ between the two lines of cells. By contrast, the repair of PSII from photodamage was suppressed in mutant cells. Addition of α-tocopherol to cultures of mutant cells returned the extent of photoinhibition to that in wild-type cells, without any effect on photodamage. The synthesis de novo of various proteins, including the D1 protein that plays a central role in the repair of PSII, was suppressed in mutant cells under strong light. These observations suggest that α-tocopherol promotes the repair of photodamaged PSII by protecting the synthesis de novo of the proteins that are required for recovery from inhibition by singlet oxygen.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Inoue
authors.forename: Kayoko
authors.initials: K
authors.lastname: Ejima
authors.forename: Eri
authors.initials: E
authors.lastname: Iwai
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hayashi
authors.forename: Jens
authors.initials: J
authors.lastname: Appel
authors.forename: Esa
authors.initials: E
authors.lastname: Tyystjärvi
authors.forename: Norio
authors.initials: N
authors.lastname: Murata
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nishiyama
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D008027:Light; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D026082:Singlet Oxygen / Q000378:metabolism; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D024502:alpha-Tocopherol / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D045332:Photosystem II Protein Complex; D026082:Singlet Oxygen; D024502:alpha-Tocopherol