title: Replacement of chlorophyll with di-vinyl chlorophyll in the antenna and reaction center complexes of the cyanobacterium Synechocystis sp. PCC 6803: characterization of spectral and photochemical properties.
abstract: Chlorophyll (Chl) a in a cyanobacterium Synechocystis sp. PCC 6803 was replaced with di-vinyl (DV)-Chl a by knock-out of the specific gene (slr1923), responsible for the reduction of a 8-vinyl group, and optical and photochemical properties of purified photosystem (PS) II complexes (DV-PS II) were investigated. We observed differences in the peak wavelengths of absorption and fluorescence spectra; however, replacement of Chl a with DV-Chl a had limited effects. On the contrary, photochemical reactions were highly sensitive to high-light treatments in the mutant. Specifically, DV-Chl a was rapidly bleached under high-light conditions, and we detected significant dissociation of complexes and degradation of D1 proteins (PsbA). By comparing the SDS-PAGE patterns observed in this study to those observed in spinach chloroplasts, this degradation is assigned to the acceptor-side photoinhibition. The delayed fluorescence in the nanosecond time region at 77 K was suppressed in DV-PS II, possibly increasing triplet formation of Chl molecules. Our findings provide insight into the evolutionary processes of cyanobacteria. The effects of pigment replacement on the optimization of reactions are discussed.
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan. tomo@z05.mbox.media.kyoto-u.ac.jp
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tomo
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ito
authors.forename: Tohru
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Michitaka
authors.initials: M
authors.lastname: Fukuya
authors.forename: Ayumi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mimuro
mesh_terms: D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D008956:Models, Chemical; D010100:Oxygen / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*
chemical_list: D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit; D002734:Chlorophyll; D010100:Oxygen