title: Activities of nucleoprotein particles derived from rat liver ribosome.
abstract: 80-S ribosomes and 60-S subunits from rat liver were treated at increasing KC1 concentrations giving protein-deficient ribosomal particles whose components were analyzed and their activity tested. Most of the activities assayed stand treatment up to KC1 concentrations of around 0.6 M; peptidyl transferase, measured by the fragment reaction, however was 50% inhibited by 0.5 M KC1 in 60-S subunits but not in 80-S ribosomes. Three proteins, L21, L26 and L31, might be implicated in this loss of activity. 60-S subunits forming part of the 80 S ribosome are more resistant to the salt treatment and the pattern of proteins released by the treatment differs from the one obtained from free 60-S subunits, implying perhaps a change of conformation of this subunit upon association to form 80-S couples. According to their resistance to release by KC1 the proteins of the large sub-unit can be divided into three groups: (1) easily removed, including proteins: L1, L11, L17 and L25 in 80-s subunits and in addition, L5, L8, L9, L13, L20, L22, L26, L29, L31 and L32/33 in 60-S subunits; (2) proteins resistant to release by high salt concentrations in 80-S ribosomes as well as in 60-S subunits, namely proteins L3, L14, L27, L36, L40, L41, X1 and X2; (3) the rest of the proteins which are released in a more or less continuous way throughout the treatment. 5 S RNA is not released by KC1 treatment at the concentrations used. The binding sites for the antibiotics trichodermin and anisomycin are affected in a different way by the salt treatment, indicating that they are structurally different.
mesh_terms: D000818:Animals; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D009698:Nucleoproteins / Q000378:metabolism*; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D051381:Rats; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D009698:Nucleoproteins; D012269:Ribosomal Proteins; D011189:Potassium Chloride