Imaginal disc ribosomal proteins of D. melanogaster

Summary The ribosomal proteins from undifferentiated imaginal discs of Drosophila melanogaster were analyzed by two-dimensional gel electrophoresis and compared with the ribosomal protein pattern of adult flies. It is shown that the ribosomal proteins from these discs are qualitatively identical with those of adult flies except that two acidic proteins are missing in the discs. This heterogeneity is discussed in terms of the functional roles these two proteins may carry in connection with disc differentiation.Paper No. 6 of the present series. Paper No. 5 is by Lambertsson, A. G. Molec. gen. Genet. 139, 145–156 (1975)     

Characterization and comparison of ribosomal proteins from two prokaryotic organisms

Ribosomal proteins from the prokaryotic bacteria. Streptococcus mutans and Escherichia coli, were separated by two dimensional gel electrophoresis as described by O'Farrell. The resulting protein spot patterns in the two types of gels are discussed in comparison with one another and with ribosomal proteins from eukaryotic organisms. More acidic proteins were found in ribosomal preparations from E. coli than from S. mutans, although this was probably a result of contamination of the former preparation with cellular components. Six ribosomal proteins from these organisms traversed to similar positions on the gels and this suggested that they were identical with respect to molecular weight and electrostatic charge. The data indicate that the six proteins were conserved through the evolution of these two prokaryotic organisms.     

The ribosomal proteins of Drosophila melanogaster. II. Comparison of protein patterns of ribosomes from larvae, pupae and adult flies by two-dimensional polyacrylamide gel electrophoresis

Summary The ribosomal proteins from two larval and two pupal stages, within 24 hours before and after pupation, respectively, and adult flies were extracted and compared by two-dimensional polyacrylamide gel electrophoresis. This technique resolved 53 larval, 50 pupal and 52 adult ribosomal proteins, forming a complex pattern. Some proteins were found only in one stage or the other. At present it is not possible, however, to classify these proteins as stage-specific. Some spots showed considerable increase in their staining intensities from one stage to the other, whereas, at the same time, other spots faded. In the ribosomal protein pattern of adult flies 3 proteins showed altered electrophoretic mobilities as compared to earlier developmental stages.Hormones involved in insect development, epigenetic control and non-ribosomal proteins are discussed as possible causes of the variations in the ribosomal protein composition.     

Adaptive Potential of Wheat Ribosomes toward Heat Depends on the Large Ribosomal Subunit and Ribosomal Protein Phosphorylation

In a study of the translational efficiency of ribosomal subunits as a function of an in vivo temperature pretreatment, ribosomes were isolated from heat-pretreated (36°C) and reference (20°C) wheat seedlings (Triticum aestivum L.). The efficiency of recombined subunits in translating polyuridylic acid was assessed. A threefold increase in the rate of incorporation of phenylalanine by ribosomes from heat-pretreated plants was due to the large ribosomal subunit. This adaptive temperature effect was not correlated with a higher thermal stability of ribosomes or subunits from heat-pretreated seedlings, and two-dimensional gel electrophoresis failed to detect structural alterations of ribosomal proteins. Phosphorylation of ribosomal proteins in vitro showed no differences between ribosomes or subunits from heat-pretreated and reference plants. Incubation with [³²P]orthophosphate in vivo led to twice the amount of phosphate in ribosomal proteins from heat-pretreated wheat seedlings. This result is important with respect to the evaluation of the molecular basis of enhanced translational efficiency of ribosomes isolated from heat-pretreated wheat seedlings.     

Ribosomal protein profiling by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for phylogenety-based subspecies resolution of Bifidobacterium longum

The taxonomic positions of the subspecies of Bifidobacterium longum (B. longum subsp. longum, subsp. infantis, and subsp. suis) have been controversial. A current proposal is that the former two species “B. infantis” and “B. suis” be unified with B. longum and all three reclassified as three subspecies. To test this proposal, ribosomal protein profiling as observed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied to the classification of 17 strains of B. longum, including three subspecies. Among 41 different kinds of ribosomal proteins selected as biomarkers whose masses were calculated from their amino acid sequences, 31-41 ribosomal proteins were observed in sample strains with the same masses as the references. The high matching rate indicates high conservation of ribosomal proteins within the sample strains, and therefore strongly supports the unification of the former species. However, the masses of some ribosomal proteins varied within species. The phylogenetic tree constructed from the profiles of ribosomal proteins matched the references, showing a clear cluster of the subsp. longum and the subsp. infantis strains. This result supports the proposal to reclassify B. longum into subsp. longum and subsp. infantis. The subsp. suis strains formed an individual sub-cluster within the infantis cluster. However, their ribosomal proteins have both characters of longum and infantis types. This result suggests that the taxonomic position of the subsp. suis should be reconsidered.     

The ribosomal proteins of Drosophila melanogaster. I. Characterization in polyacrylamide gel of proteins from larval, adult, and ammonium chloride-treated ribosomes

Summary Ribosomes were isolated from larvae and adult flies, and the purity of the preparation was checked by electron microscopy. The ribosomal proteins were extracted with cold dilute hydrochloric acid, and precipitated with cold acetone. The proteins were characterized by polyacrylamide gel electrophoresis. At pH 3.0 at least 25 bands of different color intensities were resolved, forming a complex pattern.On the basis of electrophoretic mobilities, it was shown that some ribosomal proteins are species-specific, and that larval ribosomes have three protein components more than ribosomes from adult flies.Incubation of the ribosomes with 0.75 M NH₄Cl at a low Mg⁺⁺ concentration lead to detachment of 64% of the ribosomal protein. This detachment of protein molecules was considerably reduced by a five-fold increase of Mg⁺⁺ ions.     

Synthesis of ribosomal proteins during the yeast cell cycle

The synthesis of ribosomal proteins during the cell division cycle of Saccharomyces cerevisiae has been examined. A technique was utilized whereby cells in unique phases of the cell cycle were selected from an asynchronous culture after the period of pulse labeling. Some of the proteins of the small and large ribosomal subunits were synthesized continuously throughout the cell cycle and there was no evidence of discontinuous synthesis for any of the ribosomal proteins.     

Protein metabolism of Drosophila melanogaster male accessory glands—III: Stimulation of protein synthesis following copulation

Stimulation of the accessory gland of Drosophila melanogaster males by copulation was studied at the molecular level by in vivo radiolabelling experiments. In addition, experiments were carried out to clarify the molecular basis of regulation of the gland's synthetic activityThe stimulatory effect of copulation on secretion protein synthesis is observed within minutes after copulation is terminated. Repeated copulations elicit a stronger response. The data indicate a coordinate synthesis of the secretory proteins.In a reticulocyte-lysate system with added total RNA extract from male accessory glands, secretion proteins appear as translation products. It is shown that synthesis of secretory protein messages is not enhanced by copulation and that the messages are stable.Synthesis of ribosomal proteins and ribosomal RNA increases upon copulation. The increase is observed in the time period from 1 to 5 hr after copulation. Again, the synthesis of the various ribosomal proteins is well coordinated. There is no elevation in the accumulation of ribosomal protein mRNAs after copulation.     

The Chloroplast and Cytoplasmic Ribosomes of Euglena: II. Characterization of Ribosomal Proteins

Cytoplasmic and chloroplast ribosomal proteins were isolated from Euglena gracilis and analyzed on polyacrylamide gels. Cytoplasmic ribosomes appear to contain 75 to 100 proteins ranging in molecular weight from 10,200 to 104,000, while chloroplast ribosomes appear to contain 35 to 42 proteins with molecular weights ranging from 9,700 to 57,900. This indicates that the cytoplasmic ribosomes are similar in composition to other eucaryotic ribosomes, while chloroplast ribosomes have a protein composition similar to the 70S procaryotic ribosome. The kinetics of light-induced labeling of cytoplasmic ribosomal proteins during chloroplast development has been determined, and the results are compared with the kinetics of ribosomal RNA synthesis.     

Nucleotide sequences of cloned cDNA fragments specific for six Xenopus laevis ribosomal proteins

We have previously constructed and selected six recombinant plasmids containing cDNA sequences specific for different ribosomal proteins of Xenopus laevis (Bozzoni et al., 1981). DNA cloned in these plasmids have been isolated and sequenced. Amino acid sequences of the corresponding portions of the proteins have been derived from DNA sequences; they are arginine- and lysine-rich as expected for ribosomal proteins. One of the cDNA sequences has an open reading frame also on the strand complementary to the one coding for the ribosomal protein; this fragment has inverted repeats twenty nucleotides long at the two ends. The codon usage for the six sequences appears to be non-random with some differences among the ribosomal proteins analysed.     

Biogenesis of ribosomes: free ribosomal protein pools in Escherichia coli

Proteins from ribosomal subunits (30 s and 50 s) have been fractionated into split (SP-30 and SP-50) and core (core-30 and eore-50) proteins. Antisera prepared in rabbit against them are shown to be highly group-specific as judged by the Ouchterlony (1967) double diffusion test and by precipitin reaction in solution. Various parameters which influence the immuno-precipitation of these proteins by specific antisera have been investigated. It is demonstrated that under controlled conditions this provides a sensitive and reliable method for characterization and quantitative estimation of free ribosomal proteins. The technique has been successfully applied in the investigations of various properties of free ribosomal protein pools existing in Escherichia coli. It is concluded that free ribosomal proteins in E. coli may constitute 8 to 14% of total soluble proteins under different growth conditions. Relative pool sizes of four classes of proteins expressed as a percentage of the total soluble proteins in bacteria grown in L broth (doubling period, 30 min) are estimated to be core-30, 2.1; core-50, 3.4; SP-30, 3.6; SP-50, 5.0. From the studies on bacteria grown in different media (doubling period, 30, 42 and 60 min), we further conclude that the amount of free proteins increases with the growth rate so as to constitute a constant fraction (7 to 9%) of total ribosomal proteins. Relative pool-sizes corresponding to four classes of ribosomal proteins, however, remain unaltered by different growth rate.     

The complete amino acid sequence of ribosomal protein S12 from Bacillus stearothermophilus

The amino acid sequence of ribosomal protein S12 from Bacillus stearothermophilus has been completely determined. The sequence data were mainly obtained by manual sequencing of peptides derived from digestion with trypsin, Staphylococcus aureas protease and pepsin. A few overlaps of tryptic peptides were established by DNA sequence analysis of a chromosomal fragment containing the rpsL gene coding for ribosomal protein S12. The protein contains 138 amino acid residues and has an M_r of 15208. Comparison of this sequence with the sequences of the ribosomal S12 proteins from E. coli as well as from Euglena, tobacco and liverwort chloroplasts shows that 75% of the amino acid residues are identical within the S12 proteins of all four species. Therefore, S12 is the most strongly conserved ribosomal protein known so far.     

Radioenzymatic assay for the acetohydroxy acid synthase-catalyzed synthesis of alpha-aceto-alpha-hydroxybutyrate

A method has been developed for radiolabeling small amounts of ribosomal proteins extracted from polyacrylamide gels with potassium [¹²⁵]Iiodide. The procedure was used to label even those proteins which lack tyrosine and histidine residues by the modification of proteins with methyl p-hydroxybenzimidate. Specific radioactivities obtained range from 20,000 to 200,000 cpm/μg. The method has been used in the identification of eukaryotic ribosomal proteins from rabbit reticulocytes separated by polyacrylamide/sodium dodecyl sulfate gel electrophoresis.     

The ribosomal subunit assembly line

Recent proteomic studies in Saccharomyces cerevisiae have identified nearly 200 proteins, other than the structural ribosomal proteins, that participate in the assembly of ribosomal subunits and their transport from the nucleus. In a separate line of research, proteomic studies of mature plant ribosomes have revealed considerable variability in the protein composition of individual ribosomes.