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Phylogenetic and functional features of the plastid transcription kinase cpCK2 from Arabidopsis signify a role of cysteinyl SH‐groups in regulatory phosphorylation of plastid sigma factors
Author(s) -
Türkeri Hacer,
Schweer Jennifer,
Link Gerhard
Publication year - 2012
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2011.08433.x
Subject(s) - casein kinase 2 , biochemistry , biology , serine , casein kinase 1 , phosphorylation , protein kinase a , transcription factor , plastid , arabidopsis , kinase , cysteine , microbiology and biotechnology , cyclin dependent kinase 2 , enzyme , chloroplast , gene , mutant
A plastidic serine/threonine protein kinase, initially named plastid transcription kinase (PTK) has been implicated in phosphorylation and redox control of chloroplast transcription. This kinase was later renamed as chloroplast casein kinase 2 (cpCK2) because of its physical and functional similarity to nucleocytosolic casein kinase 2 (ncCK2). It shares all four of its cysteine residues with ncCK2 from land plants, while only three of these residues are conserved in algal CK2‐type sequences, and just two in animals. Using bacterial overexpression of cpCK2 from Arabidopsis thaliana , here we show the principal features of this enzyme and assign functional determinants of its role as a transcriptional regulator in vitro . The recombinant protein is capable of using various plant sigma transcription factors as phosphorylation substrates. Electrophoretic mobility shift DNA‐binding assays reveal differential effects of sigma phosphorylation, depending on the factor and the promoter used. Treatment of the kinase with redox‐active reagents indicate a critical involvement of thiol groups in both its enzymatic activity and interaction capabilities. Mutational exchanges of cysteine to serine residues, in combination with in vitro assays, have provided clues to the possible role of individual cysteines. For instance, while Cys4 but not Cys2 is essential for activity, the latter seems to be involved in the formation of intermolecular (regulatory) disulfide bonds. Structured digital abstract• cpCK2 phosphorylates SaSig2 by protein kinase assay ( View interaction ) • cpCK2 phosphorylates AtSig6 by protein kinase assay ( View interaction ) • cpCK2 and cpCK2 bind by comigration in gel electrophoresis ( View interaction ) • cpCK2 phosphorylates AtSig1 by protein kinase assay ( View interaction ) • cpCK2 phosphorylates SaSig1 by protein kinase assay ( View interaction )