Phosphorylation of maize eukaryotic translation initiation factor on Ser2 by catalytic subunit CK2.

Alignment of eukaryotic translation initiation factor 5A (eIF5A) sequences has shown, for plants, in contrast to most other eukaryotes, the presence of N-terminal serine residue (Ser2) which could be phosphorylated by CK2. Using point directed mutagenesis, we demonstrate here that in recombinant maize ZmeIF5Awt Ser2 is exclusively phosphorylated by catalytic subunit of CK2 (CK2α), whereas its mutated variant Ser2Ala is not phosphorylated. To shed light on the physiological significance of this Ser2 phosphorylation, transient expression of fluorescence-labeled proteins was performed in maize protoplast.

Phosphorylation of maize eukaryotic translation initiation factor 5A (eIF5A) by casein kinase 2: identification of phosphorylated residue and influence on intracellular localization of eIF5A.

Maize eukaryotic translation initiation factor 5A (ZmeIF5A) co-purifies with the catalytic alpha subunit of protein kinase CK2 and is phosphorylated by this enzyme. Phosphorylated ZmeIF5A was also identified after separation of maize leaf proteins by two-dimensional electrophoresis. Multiple sequence alignment of eIF5A proteins showed that in monocots, in contrast to other eukaryotes, there are two serine/threonine residues that could potentially be phosphorylated by CK2.