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.
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.
Tomo
Tatsuya
T
Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan. tomo@z05.mbox.media.kyoto-u.ac.jp
Akimoto
Seiji
S
Ito
Hisashi
H
Tsuchiya
Tohru
T
Fukuya
Michitaka
M
Tanaka
Ayumi
A
Mimuro
Mamoru
M
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*
D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit; D002734:Chlorophyll; D010100:Oxygen