Eukaryotic ribosomal subunit anti-association activity of calf liver is contained in a single polypeptide chain protein of Mr = 25,500 (eukaryotic initiation factor 6).
A protein factor that prevents the reassociation of eukaryotic 40 S and 60 S ribosomal subunits when the Mg+ concentration is raised from 1 to 5 mM has been purified to apparent electrophoretic homogeneity from postribosomal supernatant of calf liver extracts. The purified ribosomal subunit anti-association factor is a relatively heat-sensitive protein consisting of a single polypeptide chain of apparent Mr = 25,500. Direct assay for ribosomal subunit anti-association activity indicates that the majority (greater than 90% of such an activity in calf liver extracts can be accounted for by the presence of this 25,500-dalton protein factor in the postribosomal supernatant. The ribosomal salt wash protein fractions are virtually devoid of any significant ribosomal subunit anti-association or 80 S ribosome dissociation activity. The purified anti-association factor maintains a pool of ribosomal subunits by binding to 60 S ribosomal subunits and preventing them from reassociating with 40 S ribosomal subunits, rather than by dissociating 80 S monosomes. The factor neither binds to, nor seems to interact directly with, 40 S subunits. The properties of this factor are thus similar to wheat germ ribosome dissociation factor (eukaryotic initiation factor 6) described by Russell and Spremulli ((1979) J. Biol. Chem. 254, 8796-8800.
D000818:Animals; D002417:Cattle; D008099:Liver / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000302:isolation & purification* / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics; D011817:Rabbits; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
D010448:Peptide Initiation Factors; C021019:eIF-6; D012343:RNA, Transfer; D008274:Magnesium