title: Phycobilisome linker proteins are phosphorylated in Synechocystis sp. PCC 6803.
abstract: The controversial issue of protein phosphorylation from the photosynthetic apparatus of Synechocystis sp. PCC 6803 has been reinvestigated using new detection tools that include various immunological and in vivo labeling approaches. The set of phosphoproteins detected with these methods includes ferredoxin-NADPH reductase and the linker proteins of the phycobilisome antenna. Using mutants that lack a specific set of linker proteins and are affected in phycobilisome assembly, we show that the phosphoproteins from the phycobilisomes correspond to the membrane, rod, and rod-core linkers. These proteins are in a phosphorylated state within the assembled phycobilisomes. Their dephosphorylation requires partial disassembly of the phycobilisomes and further contributes to their complete disassembly in vitro. In vivo we observed linker dephosphorylation upon long-term exposure to higher light intensities and under nitrogen limitation, two conditions that lead to remodeling and turnover of phycobilisomes. We conclude that this phosphorylation process is instrumental in the regulation of assembly/disassembly of phycobilisomes and should participate in signaling for their proteolytic cleavage and degradation.
authors.affiliation: Department für Biologie I, Bereich Botanik, Ludwig-Maximilians-Universität, Menzingerstrasse 67, 80638 München, Germany.
authors.forename: Irina
authors.initials: I
authors.lastname: Piven
authors.forename: Ghada
authors.initials: G
authors.lastname: Ajlani
authors.forename: Anna
authors.initials: A
authors.lastname: Sokolenko
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D005288:Ferredoxins / Q000737:chemistry; D008027:Light; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry; D010766:Phosphorylation; D045524:Phycobilisomes / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D046939:Synechocystis / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism
chemical_list: D005288:Ferredoxins; D045524:Phycobilisomes; D009247:NADH, NADPH Oxidoreductases; D000469:Alkaline Phosphatase; D009584:Nitrogen