title: Activation of the Stt7/STN7 Kinase through Dynamic Interactions with the Cytochrome b6f Complex.
abstract: Photosynthetic organisms have the ability to adapt to changes in light quality by readjusting the cross sections of the light-harvesting systems of photosystem II (PSII) and photosystem I (PSI). This process, called state transitions, maintains the redox poise of the photosynthetic electron transfer chain and ensures a high photosynthetic yield when light is limiting. It is mediated by the Stt7/STN7 protein kinase, which is activated through the cytochrome b6f complex upon reduction of the plastoquinone pool. Its probable major substrate, the light-harvesting complex of PSII, once phosphorylated, dissociates from PSII and docks to PSI, thereby restoring the balance of absorbed light excitation energy between the two photosystems. Although the kinase is known to be inactivated under high-light intensities, the molecular mechanisms governing its regulation remain unknown. In this study we monitored the redox state of a conserved and essential Cys pair of the Stt7/STN7 kinase and show that it forms a disulfide bridge. We could not detect any change in the redox state of these Cys during state transitions and high-light treatment. It is only after prolonged anaerobiosis that this disulfide bridge is reduced. It is likely to be mainly intramolecular, although kinase activation may involve a transient covalently linked kinase dimer with two intermolecular disulfide bonds. Using the yeast two-hybrid system, we have mapped one interaction site of the kinase on the Rieske protein of the cytochrome b6f complex.
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.).
authors.forename: Alexey
authors.initials: A
authors.lastname: Shapiguzov
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.).
authors.forename: Xin
authors.initials: X
authors.lastname: Chai
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.).
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Fucile
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.).
authors.forename: Paolo
authors.initials: P
authors.lastname: Longoni
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.).
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Departments of Molecular Biology and Plant Biology, University of Geneva, Geneva, Switzerland (A.S.); and Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China (X.C., G.F., P.L., L.Z., J.-D.R.) jean-david.rochaix@unige.ch.
authors.forename: Jean-David
authors.identifier: 0000-0001-8483-777X
authors.initials: JD
authors.lastname: Rochaix
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism; D002696:Chlamydomonas / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002734:Chlorophyll / Q000032:analysis; D045346:Cytochrome b6f Complex / Q000235:genetics / Q000378:metabolism*; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010766:Phosphorylation; D010788:Photosynthesis / Q000502:physiology; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010971:Plastoquinone / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D013194:Staining and Labeling; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D045346:Cytochrome b6f Complex; D011494:Protein Kinases; D010971:Plastoquinone