title: Dissimilarity in protein chain elongation factor requirements between yeast and rat liver ribosomes.
abstract: Factor requirements for yeast and rat liver ribosomes were determined in several different reactions using either yeast or liver factors. In polymerization assays yeast ribosomes required a factor in addition to elongation factor 1 (EF-1) and elongation factor 2 (EP-2). The third factor (EF-3) requirement was observed with EFs from either yeast or liver for both poly(U)-directed polyphenylalanine synthesis and elongation of endogenous peptidyl-tRNA. No significant effect of EF-3 was observed with liver risomes in either assay. In contrast to results with polypeptide synthesis EF-3 was not required for EF-1 dependent binding of [3H]Phe-tRNA or the translocation-dependent formation of N-acetylphenylalanylpuromycin. Up to 2-fold stimulation of the binding reaction was observed with saturating levels of either yeast or liver EF-1. No effect of EF-3 was observed on ribosome-EF-2-GDP-fusidic acid complex formation. The data suggest that the yeast EF-3 may be a loosely bound ribosomal protein which is not required for a specific step in the elongation cycle but is involved in the coordination of the partial reactions required for polymerization.
mesh_terms: D000818:Animals; D001665:Binding Sites; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D010441:Peptide Chain Elongation, Translational; D010445:Peptide Elongation Factors; D010649:Phenylalanine / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D051381:Rats; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D013045:Species Specificity
chemical_list: D010445:Peptide Elongation Factors; D010649:Phenylalanine