PHOSPHORYLATION OF WHEAT-GERM TRANSLATION ELONGATION-FACTOR-2

Phosphorylation of EF-2 by a specific Ca2+/calmodulin-dependent EF-2 k inase [E.C. 2.7.1.123] in animal cells is regarded as an important mec hanism regulating protein biosynthesis at the chain elongation step. H ere we show that wheat-germ EF-2 can be readily phosphorylated by rabb it reticulocyte EF-2 kinase. This results in inhibition of plant EF-2 activity in a poly(U)-directed cell-free translation system. Thus, EF- 2 activity in plant cells potentially can be regulated through phospho rylation. However, we failed to detect endogenous EF-2-phosphorylating activity in wheat germs either in vitro or in vivo. Furthermore, no E F-2 kinase activity was found in differentiated tissues of wheat and o ther higher plants.