Purification and properties of rabbit reticulocyte protein synthesis elongation factor 2

A homogeneous preparation of elongation factor 2 (EF-2) has been obtained from rabbit reticulocytes. EF-2, purified 1,960-fold, appears to be active as a single polypeptide chain with a molecular weight of approximately 100,000 based upon the following determinations: sodium dodecyl sulfate gel electrophoresis (95,000); sedimentation equilibrium centrifugation (112,000); gel filtration (97,000); ADP-ribosylation (103,000). The amino acid composition of rabbit reticulocyte EF-2 is almost identical with that of rat liver EF-2. The unknown amino acid in rat liver EF-2 which can be ADP-ribosylated appears also to be present in rabbit reticulocyte EF-2. A comparison of the amino acid composition of rabbit reticulocyte and rat liver EF-2 with Escherichia coli EF-G shows a high degree of similarity with only four amino acids differing by more than 10% (alanine, lysine, cysteine, and leucine).