Studies on proteins of animal ribosomes. VII. Isolation of proteins from rat liver ribosomes, their molecular weights, amino acid compositions and secondary structure

Characterisation of eukaryotic ribosomal proteins

A simple method of two-dimensional polyacrylamide gel electrophoresis is described which affords: (1) high resolution of eukaryotic ribosomal proteins; (2) good recovery of protein in the transfer from first to second dimension; and (3) characterisation of the separated proteins in terms of molecular weights and other electrophoretic properties. Using this method, we have characterised 70 proteins in rabbit reticulocyte ribosomes, 30 from the small subunit and 40 from the large subunit. The molecular weight distribution is compared with those obtained by other authors after fractionation of the proteins in two dimensions.

Studies on proteins of animal ribosomes. XXIV. Localisation of proteins in ribosomal subunits of rat liver studied by chemical substitution with p-nitrophenyl acetate and methyl acetimidate

The reaction of [3H]p-nitrophenyl acetate (NPA) or [14C]methyl acetimidate (MAI) with amino groups of ribosomal pade between the reactivity of the proteins in situ in the ribosomal subunit with that of isolated protein mixtures. In the small subunit reactivity compared with the protein mixture was only 10-65% in the case of NPA but 45 to more than 100% in the case of MAI. In the large subunit reactivity to MAI was 10-60% that of the isas a denser structure than the small one. In agreement with earlier experiments with iodoacetamide the proteins S2, 5, 7, 8, 10 and 13 of the small subunit and L15, 17, 20, 24, 25, 27, 29, 33, 34, 35 and 38 in the large subunit are quite accessible while proteins S9, 14, 19, 20, 24, 25, 27, 29 and 30 of the small subunit and L1, 7, 8, 10, 11, 19, 28, 31, and 32 of the large one are relatively inaccessible.

Eukaryotic ribosomal proteins. Molecular weights of proteins from rabbit liver subunits

The molecular weights of the proteins from rabbit liver ribosomal 40 S and 60 S subunits were determined after preliminary separation of these proteins by two-dimensional electrophoresis: each spot present in the polyacrylamide slab was cut off, eluted and rerun in a SDS one-dimensional polyacrylamide gel. The molecular weights range from 9,000 to 35,000 with a number-average molecular weight of 19,600 for the 40 S proteins, and from 9,400 to 52,000 with a number-average molecular weight of 23,600 for 60 S proteins.

Solution of ribosomal proteins under mild conditions

Ribosomal proteins from two eucaryotic species, prepared by either the guanidine . HCl or LiCl . urea method and subsequently dissolved in 8 M urea were found to be largely retained in solution after removal of the urea by dialysis against a solution of low ionic strength (0.05 M Tris . HCl, pH 7.6, 0.025 M KCl, 0.005 M magnesium acetate) and centrifugation at 100,000 times g. The protein composition of this preparation was virtually identical to that of the original urea-containing solution as determined by two-dimensional polyacrylamide gel electrophoresis. Thus, there exists a very simple method for obtaining the bulk of the ribosomal proteins in solution under conditions where ribosomes themselves are stable.