Comparison of phosphorylation of elongation factor 1 from different species by caScin kinase II

Abstract

One subunit of EF-I or EF-Ifl7 from Artemia salina, wheat germ and rabbit reticulocytes is modified by casein kinase II. The subunit corresponds to the low Mr subunit of EF-1 (26000-36000) which functions along with a higher Mr subunit (46000~8000), to catalyze the exchange of GDP for GTP on EF-lct. The factor from Artemia and wheat germ is phosphorylated directly on serine by casein kinase II whereas a modulatory compound is required for phosphorylation of EF-1 from reticulocytes. Polylysine increases the rate of phosphorylation of EF-1 from reticulocytes by 24-fold; both serine and threonine are modified. This suggests that polylysine may be substituting for a physiological regulatory compound which modulates phosphoryation in vivo.