title: The peptide microarray "ChloroPhos1.0" identifies new phosphorylation targets of plastid casein kinase II (pCKII) in Arabidopsis thaliana.
abstract: We report the development of a peptide microarray based on previously determined phosphorylation sites in chloroplast proteins. Altogether, 905 peptides were spotted as 15mers in nine replicates onto glass slides. We used the microarray for in vitro phosphorylation experiments and specifically assessed the peptide substrate spectrum of chloroplast casein kinase II (pCKII). To this end, native pCKII from Arabidopsis thaliana and Sinapis alba chloroplasts was enriched by Heparin-Sepharose chromatography and its activity on the microarray was compared to the activity of a recombinant Arabidopsis pCKII. All three kinase preparations phosphorylated a similar set of peptides that were clearly distinct from those phosphorylated by bovine heart protein kinase A (PKA) in control experiments. The majority of the pCKII phosphorylation targets are involved in plastid gene expression, supporting the earlier denomination of pCKII as plastid transcription kinase (PTK). In addition we identified Alb3 as pCKII substrate that is essential for the integration of light-harvesting complex subunits (LHC) into the thylakoid membrane. Plastid CKII phosphorylation activity was characterized in greater detail in vitro with recombinant wildtype Alb3 and phosphorylation site mutants as substrates, establishing S424 as the pCKII phosphorylation site. Our data show that the peptide microarray ChloroPhos1.0 is a suitable tool for the identification of new kinase downstream targets in vitro that can be validated subsequently by in vivo experiments.
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Schönberg
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Bergner
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Helm
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Agne
authors.affiliation: Molecular Biology of Plant Organelles, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Dünschede
authors.affiliation: Molecular Biology of Plant Organelles, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Danja
authors.initials: D
authors.lastname: Schünemann
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany; Steinbeis-Forschungszentrum, Peptide Microarrays, Halle (Saale), Germany.
authors.forename: Mike
authors.initials: M
authors.lastname: Schutkowski
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Sacha
authors.initials: S
authors.lastname: Baginsky
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D047390:Casein Kinase II / Q000378:metabolism*; D010766:Phosphorylation; D018087:Plastids / Q000201:enzymology*; D040081:Protein Array Analysis / Q000379:methods*
chemical_list: D029681:Arabidopsis Proteins; D047390:Casein Kinase II