title: Reductive alkylation of mammalian ribosomes.
abstract: 40- and 60-S ribosomal subunits and 80-S ribosomes from rat liver were highly labelled by reductive methylation using formaldehyde and sodium boro-[3H] hydride, under conditions which did not decrease their activity in poly-U-directed polyphenylalanine synthesis. Dissociation of the monosomes, subunits dimers, and polysomes into free subunits was observed after methylation. Free proteins labelled after extraction from the ribosomal subunits incorporated 7 times more radioactivity than when labelled in the subunits. Proteins extracted from methylated subunits and ribosomes were analyzed by two-dimensional gel electrophoresis, and the radioactivity of each protein was compared to that of the same free protein. A classification of the proteins was established according to their accessibility to the reagents in the subunits and the ribosomes.
mesh_terms: D000409:Alanine; D000818:Animals; D001894:Borohydrides; D005557:Formaldehyde; D008099:Liver / Q000648:ultrastructure; D046911:Macromolecular Substances; D008745:Methylation; D008970:Molecular Weight; D010452:Peptide Biosynthesis; D011072:Poly U / Q000378:metabolism; D051381:Rats; D012269:Ribosomal Proteins / Q000032:analysis; D012270:Ribosomes / Q000378:metabolism
chemical_list: D001894:Borohydrides; D046911:Macromolecular Substances; D012269:Ribosomal Proteins; D005557:Formaldehyde; D011072:Poly U; D000409:Alanine