title: Synthesis of ribosomal structural proteins by postmitochondrial supernatant from regenerating rat liver.
abstract: 1. When the postmitochondrial supernatant (PM-supernatant) from regenerating rat liver was incubated with [3H]methionine, the incorporation of [3H]methinoine into the N-terminal residues of nascent peptides on ribosomes was observed. This incorporation was sensitive to a low cocentration (2X10(-6) M) of pactamycin. The results suggest that PM-supernatant has low but definite activity for the initiation of nascent protein synthesis. Polysomes and cell sap from regenerating rat liver showed negligible pactamycin-sensitive incorporation of [3H]methionine into N-terminal, residues of nascent peptides. 2. PM-supernatant from regenerating rat liver was incubated with [35S]methionine in the complete reaction mixture. After addition of ribosomal proteins labelled with [3H]methionine in vivo, ribosomal structural proteins were prepared from the incubation mixture by acetic acid extraction, CM-cellulose column chromatography, Sephadex G-200 gel filtration and finally by two-dimensional acrylamide gel electrophoresis. Incorporation was observed in the greater part of ribosomal proteins on the two dimensional gel. From the 35S-to-3H ratios of ribsomal protein fractions during the purification procedures, it appeared that the incorporation of labelled methionine into the ribosomal proteins by PM-supernatant was about 3% of that into the total proteins. When [3H]leucine was used, the values were about 4% in the same cell-free system and 5 to 6% in in vivo labelling. The results indicate that ribosomal proteins are synthesized with high efficiency by PM-supernatant from regenerating rat liver.
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D003600:Cytosol / Q000378:metabolism; D006657:Histones / Q000096:biosynthesis; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008115:Liver Regeneration; D010142:Pactamycin / Q000494:pharmacology; D011132:Polyribosomes / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D012313:RNA / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D012156:Reticulocytes / Q000378:metabolism; D012269:Ribosomal Proteins / Q000096:biosynthesis*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D006657:Histones; D012269:Ribosomal Proteins; D010142:Pactamycin; D012313:RNA