Phosphorylation of elongation factor 1 beta by an endogenous kinase affects its catalytic nucleotide exchange...

Elongation factor 1 beta (EF-1 beta) from Artemia is phosphorylated to a high percentage at serine 89 by an endogenous kinase present in EF-1 beta gamma. Protein sequencing of EF-1 beta revealed that this serine residue is located N-terminally of an acidic cluster of amino acids, (formula; see text) which is critical for casein kinase II-type substrate recognition. A number of compounds known to influence casein kinases were studied, revealing that the kinase activity as present in EF-1 beta gamma belongs to the class of casein kinase II. The rate of nucleotide exchange on EF-1 alpha as catalyzed by EF-1 beta was found to be affected reversibly by the state of phosphorylation of EF-1 beta. In the presence of dephosphorylated EF-1 beta, the exchange rate is almost twice as large compared to the rate in the presence of phosphorylated EF-1 beta. Rephosphorylation of dephosphorylated EF-1 beta diminishes the activity of the protein again. The role of casein kinase II-type enzymes in modulating the function of proteins involved in polypeptide synthesis is discussed.