The phosphorylation of protein S6 in the newly-synthesized cytoplasmic ribosomes of hamster fibroblasts.

Ribosomes were isolated from baby hamster kidney fibroblasts, either 20 min or 2 days after labelling with radioactive amino acids, and their proteins subjected to two-dimensional polyacrylamide gel electrophoresis. No significant differences were observed between the amounts of radioactivity associated with the position of the phosphorylated derivatives of protein S6. This suggests that the phosphorylation is unlikely to be important in ribosomal biogenesis or extranuclear transport.