title: The mechanism of action of eukaryotic initiation factor 4C in protein synthesis.
abstract: Binding of eukaryotic initiation factor 4C (eIF-4C) to a 40-S initiation complex could be detected by analysis of assay mixtures for 40-S initiation complex formation on columns of Sepharose 6B and on sucrose gradients. On Sepharose 6B columns an almost stoichiometric binding of [14C]eIF-4C was observed, provided that eIF-1, eIF-2, eIF-3, Met-tRNAf and mRNA were included in the assay mixtures. On sucrose gradients the presence of 0.5 microM edeine was an additional prerequisite for stable binding of eIF-4C. The presence of eIF-4C on the 40-S initiation complex resulted in a pronounced increase of its stability, which might explain the observed stimulatory effect of the factor on the binding of Met-tRNAf into initiation complexes. The interaction between eIF-4C and the small ribosomal subunit presumably occurs at an early stage of the initiation process, since eIF-4C was capable of dissociating 80-S ribosomes into subunits. Protein synthesis in a 'pH-5' assay was almost totally dependent on the addition of eIF-4C, when the assay was performed with purified, nearly homogeneous, initiation factors.
mesh_terms: D000818:Animals; D004486:Edeine / Q000494:pharmacology; D015977:Eukaryotic Initiation Factor-1; D007700:Kinetics; D008715:Methionine; D008970:Molecular Weight; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D012156:Reticulocytes / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D015977:Eukaryotic Initiation Factor-1; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; C026022:eukaryotic peptide initiation factor-1A; D004486:Edeine; D012343:RNA, Transfer; D008715:Methionine