title: The phosphorylation status of the chloroplast protein kinase STN7 of Arabidopsis affects its turnover.
abstract: The chloroplast serine-threonine protein kinase STN7 of Arabidopsis (Arabidopsis thaliana) is required for the phosphorylation of the light-harvesting system of photosystem II and for state transitions, a process that allows the photosynthetic machinery to balance the light excitation energy between photosystem II and photosystem I and thereby to optimize the photosynthetic yield. Because the STN7 protein kinase of Arabidopsis is known to be phosphorylated at four serine-threonine residues, we have changed these residues by site-directed mutagenesis to alanine (STN7-4A) or aspartic acid (STN7-4D) to assess the role of these phosphorylation events. The corresponding mutants were still able to phosphorylate the light-harvesting system of photosystem II and to perform state transitions. Moreover, we noticed a marked decrease in the level of the STN7 kinase in the wild-type strain under prolonged state 1 conditions that no longer occurs in the STN7-4D mutant. The results suggest a possible role of phosphorylation of the STN7 kinase in regulating its turnover.
authors: Department of Molecular Biology, University of Geneva, 1211 Geneva, Switzerland.
authors: Adrian
authors: A
authors: Willig
authors: Alexey
authors: A
authors: Shapiguzov
authors: Michel
authors: M
authors: Goldschmidt-Clermont
authors: Jean-David
authors: JD
authors: Rochaix
mesh_terms: D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000235:genetics; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010766:Phosphorylation; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D001224:Aspartic Acid; D017346:Protein Serine-Threonine Kinases; C497212:STN7 protein, Arabidopsis; D000409:Alanine