The movement protein (MP) of Tomato mosaic virus (ToMV) was reported previously by us to be phosphorylated in vitro by a cellular protein kinase(s) that exhibited several characteristics of casein kinase 2 (CK2). To characterize further this CK2-like cellular kinase, we have cloned cDNAs encoding the CK2 catalytic subunit from tobacco and compared the properties of the recombinant protein with those of the CK2-like cellular kinase. The recombinant CK2 catalytic subunit formed a complex with ToMV MP and phosphorylated it, similar to the CK2-like cellular kinase. Phosphoamino acid analyses of various mutant MPs altered near the C terminus revealed that the recombinant CK2 catalytic subunit phosphorylated serine-261, while the CK2-like cellular kinase phosphorylated both serine-261 and threonine-256. Both kinases were suggested to phosphorylate an additional serine residue(s) in regions other than the C-terminal peptide. The results are consistent with our previous prediction of involvement of CK2 in phosphorylation of ToMV MP.
ASJC Scopus subject areas