JBC, Vol. 252, Issue 17, 6217-6221, Sep, 1977
Ethionine and the phosphorylation of ribosomal protein S6
M. A. Treloar, M. E. Treloar and R. Kisilevsky
Ribosome phosphorylation was studied by monitoring the phosphorylation
state of small subunit protein S6 as visualized on two-dimensional
electrophoretograms of ribosomal proteins isolated from rat liver. No
phosphorylation of S6 was observed under conditions of ethionine-induced
inhibition of protein synthesis. Moderate phosphorylation, detected as the
appearance of S6 and four or five phosphorylated derivatives, was observed
in saline-treated animals. Reversal of ethionine-induced inhibition of
protein synthesis by treatment with adenine led to extensive
phosphorylation of S6. A model for protein synthesis which includes
requisite phosphorylation of ribosomes during initiation is proposed.
Cyclic adenosine 3':5'-monophosphate concentration was significantly
elevated in liver of both ethionine- and ethionine plus adenine-treated
rats, relative to that of saline-treated animals.