Abstract
The changes in protein phosphorylation during induction and deinduction of peroxisome proliferation in rat liver by three types of proliferators were studied by in vitro phospho-rylation assay. Among the variously phosphorylated proteins, an increase during induction and a decrease during deinduction in phosphorylation of P 100, a cytosolic protein having a molecular weight of 100 kDa, was most remarkable. The time course of enhance-ment of phosphorylation by the administration of the proliferators, however, was not parallel with proliferation of peroxisome but with increase in the liver DNA content. Amino acid sequencing of the protein indicated the identity of its N-terminal 17 amino acid residues with those of elongation factor 2 (EF 2). Increase in the amount of EF 2 by peroxisome proliferators was confirmed by immunoblotting and this was almost parallel with peroxisome proliferation, suggesting that both increase in the amount of EF 2 and some changes in phosphorylation activities account for a large increase in in vitro phosphorylation of EF 2 by the administration of peroxisome proliferators.
