title: Role of two forms of the D1 protein in the recovery from photoinhibition of photosystem II in the cyanobacterium Synechococcus PCC 7942.
abstract: The study of turnover of two distinct forms of the photosystem II (PSII) D1 protein in cells of the cyanobacterium Synechococcus PCC 7942 showed that the 'high-light' form D1:2 is degraded significantly faster at 500 microE m(-2) s(-1) as compared with 50 microE m(-2) s(-1) while the degradation rates of the 'low-light' form D1:1 under low and high irradiance are not substantially different. Consequently, the D1:1 turnover does not match photoinactivation of PSII under increased irradiance and therefore the cells containing this D1 form exhibit a decrease in the PSII activity. Monitoring of the content of each D1 form during a recovery from growth-temperature photoinhibition showed a good correlation between the synthesis of D1:2 and restoration of the PSII activity. In contrast, when photoinhibitory treatment was conducted at low temperature, a fast recovery was not accompanied by the D1:2 accumulation. The data suggest that photoinactivation at growth temperature results in a modification of PSII that inhibits insertion of D1:1 and, therefore, for restoration of the photochemical activity in the photoinactivated PSII complexes the D1:2 synthesis is needed. This may represent the primary reason for the requirement of psbAII/psbAIII expression under increased irradiance.
authors.affiliation: Laboratory of Photosynthesis, Institute of Microbiology, Academy of Sciences, Opatovický mlýn, Czech Republic. komenda@alga.cz
authors.forename: J
authors.initials: J
authors.lastname: Komenda
mesh_terms: D000458:Cyanobacteria / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D020033:Protein Isoforms / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D020033:Protein Isoforms; D012293:Rifampin