The formation and stability of the hypusine containing protein in Chinese hamster ovary cells

Hypusine-containing protein identified as eukaryote initiationtranslation factor 4D was labeled with [ 14C]spermidine in logarithmically growing Chinese hamster ovary cells. Radioautography of the cellular proteins separated by polyacrylamide gel electrophoresis showed the label in a single protein of 18000 Mr. Time course analysis showed that this protein remained undegraded for up to 72 hours after its synthesis. Radioactivity present in the amino acid hypusine, isolated after acid hydrolysis, remained constant during the same period of time. These results indicate that the hypusine-containing protein has a long half-life.