Effects of ethionine treatment of protein-synthesizing apparatus of rat liver 80 S ribosomes and 40 S ribosomal subunits.
The inhibitory effects of ethionine treatment of female rats for 4 h on the protein-synthesizing machineries of 80 S ribosomes and 40 S ribosomal subunits of the liver were investigated. The following results were obtained. (1) The translation of globin mRNA by 80 S ribosomes or 40 S ribosomal subunits, in combination with mouse 60 S subunits, was markedly inhibited by ethionine treatment in a complete cell-free system containing partially purified initiation factors of rabbit reticulocytes and the rat liver pH 5 fraction. (2) The polysome formation of 80 S ribosomes in the complete system described above was inhibited by ethionine treatment. Similar inhibitions by ethionine treatment were observed in the case of incubation of 40 S subunits with reticulocyte lysate, although the polysome formation was rather low even in the case of control 40 S subunits. (3) The pattern of CsCl isopycnic centrifugation of rat liver native 40 S subunits uniformly labeled with [14C]- or [3H]orotic acid showed that the content of non-ribosomal proteins of native 40 S subunits was decreased by ethionine treatment. The analysis of proteins of native 40 subunits by SDS-polyacrylamide slab gel electrophoresis revealed that eIF-3 subunits and two unidentified protein fractions of molecular weight of 2.3.10(4) and 2.1.10(4) were decreased in ethionine-treated rate liver. (4) 40 S subunits from ethionine-treated or control rat livers were labeled with N-[3H]ethylmaleimide or N-[14C]ethylmaleimide, and the 3H to 14C ratios of individual 40 S proteins on two-dimensional polyacrylamide gel electrophoresis were measured. The results suggested that the conformation of rat liver 40 S subunits was changed by ethionine treatment. (5) These results may indicate that ethionine treatment decreases the activity of rat liver 40 S subunits for the interaction with initiation factors, especially eIF-3, as the results of conformational changes of 40 S subunits.
D000818:Animals; D005001:Ethionine / Q000494:pharmacology*; D039621:Eukaryotic Initiation Factor-3; D005260:Female; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D010448:Peptide Initiation Factors / Q000235:genetics / Q000302:isolation & purification; D014176:Protein Biosynthesis / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012269:Ribosomal Proteins / Q000235:genetics; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*
D039621:Eukaryotic Initiation Factor-3; D010448:Peptide Initiation Factors; D012269:Ribosomal Proteins; D005001:Ethionine