title: The p23 co-chaperone protein is a novel substrate of CK2 in Arabidopsis.
abstract: The ubiquitous Ser/Thr protein kinase CK2, which phosphorylates hundreds of substrates and is essential for cell life, plays important roles also in plants; however, only few plant substrates have been identified so far. During a study aimed at identifying proteins targeted by CK2 in plant response to salicylic acid (SA), we found that the Arabidopsis co-chaperone protein p23 is a CK2 target, readily phosphorylated in vitro by human and maize CK2, being also a substrate for an endogenous casein kinase activity present in Arabidopsis extracts, which displays distinctive characteristics of protein kinase CK2. We also demonstrated that p23 and the catalytic subunit of CK2 interact in vitro and possibly in Arabidopsis mesophyll protoplasts, where they colocalize in the cytosol and in the nucleus. Although its exact function is presently unknown, p23 is considered a co-chaperone because of its ability to associate to the chaperone protein Hsp90; therefore, an involvement of p23 in plant signal transduction pathways, such as SA signaling, is highly conceivable, and its phosphorylation may represent a fine mechanism for the regulation of cellular responses.
authors: Department of Biological Chemistry and Venetian Institute of Molecular Medicine, University of Padova, Viale G. Colombo, 3, 35131 Padova, Italy.
authors: Kendra
authors: K
authors: Tosoni
authors: Alex
authors: A
authors: Costa
authors: Stefania
authors: S
authors: Sarno
authors: Stefano
authors: S
authors: D'Alessandro
authors: Francesca
authors: F
authors: Sparla
authors: Lorenzo A
authors: LA
authors: Pinna
authors: Michela
authors: M
authors: Zottini
authors: Maria
authors: M
authors: Ruzzene
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D047390:Casein Kinase II / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010936:Plant Extracts; D011485:Protein Binding; D021381:Protein Transport; D011994:Recombinant Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013379:Substrate Specificity; D020349:Surface Plasmon Resonance
chemical_list: D029681:Arabidopsis Proteins; D010936:Plant Extracts; D011994:Recombinant Proteins; D047390:Casein Kinase II