title: Phosphoproteomics of Arabidopsis chloroplasts reveals involvement of the STN7 kinase in phosphorylation of nucleoid protein pTAC16.
abstract: Light-regulated protein kinases STN7 and STN8 phosphorylate thylakoid membrane proteins and also affect expression of several chloroplast proteins via yet unknown mechanisms. Comparative phosphoproteomics of acetic acid protein extracts of chloroplasts from Arabidopsis thaliana wild type, stn7, stn8 and stn7stn8 mutants yielded two previously unknown findings: (i) neither STN7 nor STN8 kinase was required for phosphorylation of Ser-48 in Lhcb1.1-1.3 proteins; and (ii) phosphorylation of Thr-451 in pTAC16 protein was STN7-dependent. pTAC16 was found distributed between thylakoids and nucleoid. Its knockout did not affect the nucleoid protein composition and the Thr-451 phosphorylated protein was excluded from the nucleoid. Thr-451 of pTAC16 is conserved in all studied plants and its phosphorylation may regulate membrane-anchoring functions of the nucleoid.
authors.affiliation: Division of Cell Biology, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Ingelsson
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Vener
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D004789:Enzyme Activation / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation / Q000528:radiation effects; D011494:Protein Kinases / Q000172:deficiency / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000378:metabolism*; D021381:Protein Transport / Q000528:radiation effects; D040901:Proteomics; D013912:Threonine; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects; D014158:Transcription, Genetic / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D045342:Light-Harvesting Protein Complexes; D010750:Phosphoproteins; C572958:pTAC16 protein, Arabidopsis; D013912:Threonine; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C497212:STN7 protein, Arabidopsis; C504925:STN8 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases