Number and molecular weights of the basic proteins of rat liver ribosomes

Binding of 16S rRNA to chloroplast 30S ribosomal proteins blotted on nitrocellulose

Protein-RNA associations were studied by a method using proteins blotted on a nitrocellulose sheet. This method was assayed with Escherichia Coli 30S ribosomal components. In stringent conditions (300 mM NaCl or 20 degrees C) only 9 E. coli ribosomal proteins strongly bound to the 16S rRNA: S4, S5, S7, S9, S12, S13, S14, S19, S20. 8 of these proteins have been previously found to bind independently to the 16S rRNA. The same method was applied to determine protein-RNA interactions in spinach chloroplast 30S ribosomal subunits. A set of only 7 proteins was bound to chloroplast rRNA in stringent conditions: chloroplast S6, S10, S11, S14, S15, S17 and S22. They also bound to E. coli 16S rRNA. This set includes 4 chloroplast-synthesized proteins: S6, S11, S15 and S22. The core particles obtained after treatment by LiCl of chloroplast 30S ribosomal subunit contained 3 proteins (S6, S10 and S14) which are included in the set of 7 binding proteins. This set of proteins probably play a part in the early steps of the assembly of the chloroplast 30S ribosomal subunit.

Ribosomal proteins of Thermomyces lanuginosus--characterisation by two-dimensional gel electrophoresis and differential disassembly

One- and two-dimensional gel electrophoresis were employed to characterise the proteins derived from the ribosomes of the thermophilic fungus Thermomyces lanuginosus. Approximately 32 (29 basic and 3 acidic) and 45 (43 basic and 2 acidic) protein spots were resolved from Th. lanuginosus small and large ribosomal subunits, respectively. The molecular weight of the small subunit proteins ranged from 9,800-36,000 Da with a number average molecular weight of 20,300 Da. The molecular weight range for the large subunit proteins was 12,000-48,500 Da with a number average molecular weight of 25,900 Da. Most proteins appeared to be present in unimolar amounts. These data are comparable with but not identical to those from other eukaryotic ribosomes. The sensitivities of the ribosomal proteins to increasing concentrations of NH4Cl were also evaluated by two-dimensional gel electrophoresis. Most ribosomal proteins were gradually released over a wide range of salt concentrations but some were preferentially enriched in one or two salt conditions.

Ribosomal proteins of Tetrahymena thermophila. Correlation of one- and two-dimensional electrophoretic migration patterns and characterization of additional small and large subunit proteins

Further analysis of the protein complement of the cytoplasmic ribosome of the protozoon Tetrahymena thermophila has led to the identification and characterization of seven additional proteins, three in the small and four in the large subunit of this ribosome. Several of these proteins are poorly soluble or insoluble in the absence of high concentrations of urea and are not seen in the electrophoretic distribution patterns of ribosomal proteins in two-dimensional polyacrylamide gels unless 6 M urea is added to electrode buffers in contact with protein samples (first dimension) and first-dimension gels (second dimension). The migration patterns of the 40S and 60S subunits of the T. thermophila ribosome in one-dimensional polyacrylamide SDS gels and in two-dimensional gels prepared by means of the basic-acidic system of Kaltschmidt and Wittmann**, and the basic-SDS system of Zinker and Warner*** have been correlated.

Identification of an Escherichia coli S1-like protein in the spinach chloroplast ribosome

Antibodies directed against E. coli ribosomal protein S1 were used in immunoblotting assays to search for an S1-like protein in the ribosome of spinach chloroplast. An immunological cross-reaction was reproducibly detected on the blots and inhibition experiments have demonstrated its specificity. The chloroplastic ribosomal protein which has epitopes common to antigenic determinants of the E. coli protein S1 was identified as being protein S2/S3.

Studies on interaction of 5 S RNA with ribosomal proteins

Proteins of the large ribosomal subunit of rat liver (TP 60) were immobilized by diffusion transfer onto nitrocellulose after two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Incubation of the TP 60 blots with 32P-labeled 5 S RNA under defined ionic conditions (300 mM KCl, 20 mM MgCl2) resulted in specific binding to a limited set of ribosomal proteins consisting of proteins L3, L4, L6, L13/15 and--to a lesser extent--L7 and L19. Under identical conditions, blots with proteins of the small ribosomal subunit (TP 40) did not bind 5 S RNA.

Evidence for major differences in ribosomal subunit proteins from Plasmodium berghei and rat liver

Purified polysomes were isolated in high yield from the erythrocytic stages of the rodent malaria parasite, Plasmodium berghei, and from rat liver. Proteins extracted from the ribosomal subunits derived from these polysomes were fractionated and their number and molecular weights were estimated by two-dimensional polyacrylamide gel electrophoresis. Plasmodial small ribosomal subunits contained 30 proteins ranging in apparent molecular size from 11.7 to 40.7 kDa, while large subunits contained 35-36 proteins ranging from 12.1 to 42.6 kDa. None of these parasite proteins was shared by the two subunits nor altered in electrophoretic mobility by radioiodination. Rat liver 40 S ribosomal subunit proteins numbered 30 and ranged from 9.2 to 37.5 kDa, while liver 60 S subunits contained 41-43 proteins with apparent molecular sizes of 10.3-45.2 kDa. Coelectrophoresis of trace amounts of radioiodinated P. berghei ribosomal subunit proteins and stainable quantities of liver proteins demonstrated that most of these 139 parasite and host ribosomal proteins possessed different two-dimensional electrophoretic mobilities under the conditions of this study. Based upon a comparative analysis of P. berghei and rodent ribosomal RNA and these data, it was concluded that parasite and host ribosomes contain distinct ribosomal RNAs and ribosomal proteins.

Affinity labelling of rat liver ribosomal protein S26 by heptauridylate containing a 5'-terminal alkylating group

Heptauridylate bearing a radioactive alkylating [14C]-4-(N-2-chloroethyl-N-methylamino)benzylamine attached to the 5'-phosphate via amide bond, was bound to ribosomes and small ribosomal subunits from rat liver which thereby were coded to bind N-acylated Phe tRNA. After completion of the alkylating reaction and subsequent hydrolysis of the phosphamide bond ribosomal proteins were isolated. Radioactivity was found covalently associated preferentially with protein S26 and, to a very small extent, with proteins S3 and S3a. The affinity labelling reaction could be abolished by (pU)14 and poly(U). From the results it is concluded that ribosomal protein S26 is located at the mRNA binding site of rat liver ribosomes.

Modification of ribosomal proteins in sea urchin eggs following fertilization

Analysis of the ribosomal proteins in sea urchin eggs by two-dimensional polyacrylamide gel electrophoresis revealed postfertilization changes in the proteins of both the small and the large subunits. Five egg-ribosomal proteins (S7, S16, S19, L19, L31) appeared to undergo rapid changes to the corresponding embryo-specific proteins. These changes were completed within 30 min after fertilization, and identical electrophoretic patterns were observed among the different developmental stages of embryos. One of the five proteins, S7, showed an increase in the phosphorylated form. The remainder showed qualitative shifts to the corresponding embryo-specific proteins; however, peptide map analyses revealed the existence of common structural units between the corresponding proteins. These modifications were observed in the three species of sea urchin studied (Pseudocentrotus depressus, Hemicentrotus pulcherrimus and Anthocidaris crassispina), except in the case of one protein (L31). Purification of ribosomes by different procedures based on high-salt treatment gave the same results with respect to the egg-specific and embryo-specific proteins.

Ribosomal subunits and ribosomal proteins of Tetrahymena thermophila. Effect of the presence of iodoacetamide during ribosome extraction on the properties of the subunits

Proteolytic degradation of ribosomal proteins occurs during the preparation of subunits of the cytoplasmic ribosomes of the protozoa Tetrahymena thermophila and the isolated subunits are inactive. Addition of 5 mM iodoacetamide to cell suspensions before extraction inhibits proteolytic activity and permits isolation of active subunits. The protein complements of these subunits have been characterized in two different two-dimensional electrophoretic systems, and their molecular weights have been determined.

Ribosomal proteins of sea urchin eggs. I. Characterization of cytoplasmic ribosomal proteins

Ribosomal proteins from the eggs of sea urchin, Pseudocentrotus depressus, were analyzed by two-dimensional polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. Thirty different proteins including three acidic proteins were detected in the small subunit. The large subunit was found to contain at least 43 different proteins, 42 basic and one acidic. The ribosomal proteins from the small subunit have molecular weights ranging from 11,900 to 51,700 (average molecular weight: 25,600). The molecular weights of the large subunit proteins range from 12,700 to 76,300 (average molecular weight: 28,700).

The anomalous migration during two-dimensional gel electrophoresis of eukaryotic ribosomal proteins with oxidised thiol groups

Two-dimensional gel electrophoresis of eukaryotic ribosomal proteins under conditions in which thiol groups are not maintained in a reduced state has been found to cause marked changes in the migration of certain proteins, apparently due to the formation of intramolecular disulphide bridges. The results suggest that certain previously designated eukaryotic ribosomal proteins are not, in fact, unique species.

Studies on ribosomal proteins in the cellular slime mold Dictyostelium discoideum. Resolution, nomenclature and molecular weights of proteins in the 40-S and 60-S ribosomal subunits

This study is concerned with the identification and subunit localization of ribosomal proteins in Dictyostelium discoideum. The characterization is based on the resolution of ribosomal proteins by various methods of electrophoresis. 34 and 42 unique proteins were identified in the 40-S and 60-S ribosomal subunits respectively. The total mass of proteins in the 40-S subunit was 746,100 daltons and 981,900 daltons in the 60-S subunit. The molecular weights of individual proteins in the 40-S subunit ranged from 13,200 to 40,900 with a number-average molecular weight of 21,900. The molecular weight range for the 60-S subunit was 13,800--51,100 with a number-average molecular weight of 23,400. The 80-S ribosome contained 78 proteins, two of which were lost upon its dissociation into subunits. All the proteins of the 40-S and 60-S subunits could be identified individually in a 80-S map as well as in unfractionated proteins from whole cells. Purification of ribosomes in high-ionic-strength buffers resulted in non-specific loss of the various proteins from the 40-S and 60-S subunits. In addition, the undissociated ribosomes contained about 10 acidic proteins in the molecular weight range 50,000--100,000, which were retained after washing the ribosomes in high-salt buffers. They were found in polysomes, run-off ribosomes and could also be identified in the 40-S subunit after dissociation.

Disulfide interaction in situ between two neighbouring proteins in mammalian 60-S ribosomal subunits. Isolation of the contact region of the larger protein

A disulfide complex is formed in situ under gentle conditions between two neighbouring proteins in the 60-S subunits of mammalian ribosomes. The proteins have been identified as L 4 and L 29. The complex is easily isolated from whole ribosomes, and can be utilized for preparing the two proteins in a very pure state for further characterization. Chymotryptic cleavage of the complex or the isolated larger protein (L 4) in the presence of SDS produces two unequal fragments of this protein in nearly quantitative yield. The smaller fragment (approx. 12 000 daltons) contains the contact sequence. Only this fragment of protein L 4 is labelled when rat liver ribosomes are incuabted with iodo[14C]acetate under conditions of complex formation. Protein L 29 is resistant to chymotrypsin in the presence of sodium dodecyl sulfate.

Spot position of rat liver ribosomal proteins by four different two-dimensional electrophoreses in polyacrylamide gel

Separation of the proteins from rat liver 40S and 60S ribosomal subunits and polysomes was done in four different two-dimensional polyacrylamide gel electrophoresis systems. The first dimension was run at acidic or basic pH, the second dimension either with sodium dodecyl sulphate or at acidic pH in 18% acrylamide. The position of each individual protein of both subunits and polysomes was determined in each system. This identification resulted from a new method avoiding any pervious purification of individual proteins. The new "proposed uniform nomenclature for mammalian ribosomal proteins" (McConkey et al. in press) was used for numbering the proteins in the four systems.