Ribosome Dimers Research Articles

Ribosomal dimers produced by dimers of aurintricarboxylic acid

Aurintricarboxylic acid (ATA) inhibits protein synthesis in various cell-free systems most likely by interacting with 30 S ribosomal proteins [I]. The blockage is specific for the binding of messengerRNA to the ribosome [2-4]. The binding of ATA to the ribosome itself does not depend on the presence of mRNA. In Escherichia coli considerable knowledge exists concerning the primary structure of the 16 S RNA and the 21 different proteins present in the small ribosomal subunit [6-81 and the topology of these proteins within the 30 S particle has been electron-microscopically studied [9-l 21. The functional roles of some of the individual proteins have been deduced from reconstitution experiments in vitro or from analyses of various mutant ribosomes resistant to ribosomal inhibitors. Thus the way to correlate certain defined translational functions with relevant regions of the ribosomal images visible in the electron microscope has been explored. The present study was undertaken in order to visualize directly the binding of ATA to ribosomes and their subunits using dimers of the drug.

Effects of epileptic seizures on brain ribosomes: mechanism and relationship to cerebral energy metabolism.

Abstract—Epileptic seizures were induced electrically in rats paralyzed and ventilated with oxygen. Dissociation of brain polysomes and increase in ribosomal dimers were observed after multiple (25 or more) seizures, but were not seen after shorter treatments (up to 10 seizures). Polysomal dissociation and dimer formation occurred in vivo and were accompanied by decreased amino acid incorporation into brain proteins in cell‐free systems in vitro. These events paralleled changes in brain energy reserves rather than changes in behavior.

Polysomal RNA in Semliki Forest virus infected Aedes albopictus cells.

Polysomes from Aedes albopictus cells were identified by their rapid labelling with radioactive amino acids and their sensitivity to EDTA, RNase and puromycin. The major ribosome component in cytoplasmic extracts had a sedimentation coefficient of approx. 95S and may be a ribosome dimer. In Semiki Forest virus infected Aedes albopictus cells, 42S and 26S RNA were the major virus RNA species detected up to 10 h post infection. Virus RNA was detected in association with pre-labelled ribosomes and banded at a buoyant density of 1-55 g/ml. 42S, 38S and 26S virus RNA species were associated with polysomes.

Interaction of the 5′-ends of 28S RNA in dimerization of hamster ribosomes

Free ribosomes extracted from hamster cells and 28S RNA purified from these ribosomes are known to form dimers. We find that spleen phosphodiesterase inhibits ribosomal dimer formation, but only when a free 5'-hydroxyl end group, produced by the action of alkaline phosphatase, is present. Hence, formation of dimer ribosomes probably involves interaction at or near the phosphorylated 5'-ends of 28S RNA. Dimer RNA molecules show a modal length, when measured on electrom micrographs, of 2.1 mum, which is about double the length of 28S RNA. Electron micrographs of 115S dimer ribosomes often show profiles consistent with our interpretation that in dimers the 28S RNA chains are loosely linked by their 5'-ends.

Electron microscopic localization of two proteins on the surface of the 50 S ribosomal subunit of Escherichia coli using specific antibody markers

A method to localize individual proteins on the surface of the ribosomal subunit was developed. The method uses specific immunoglobulins G against proteins under examination. The antibodies are combined with the ribosomes to give rise to ribosome dimers linked by the bivalent antibody. The Fab arm of the Y shaped antibody points to the position of the protein the antibody was prepared against. Using this method, two ribosomal proteins (L1, L19) ‡ ‡ Nomenclature of the ribosomal proteins according to Kaltschmidt & Wittmann (1970). were located on two defined shapes of the 50 S ribosomal subunit.

Electrophoretic separation of Escherichia coli ribosomal particles on polyacrylamide gels.

Escherichia coli ribosomes display a remarkable heterogeneity when submitted to polyacrylamide‐gel electrophoresis (4% acrylamide). Both the 70‐S ribosomes and 50‐S ribosomal subunits are resolved into at least four and the 30‐S ribosomal subunits into three particle subclasses.After reversal of the current, all particles refocus into one single band at the origin. Ribosomes recovered from the gel after electrophoresis have retained some 40–100% of their capacity to synthesize peptide bonds. Their sedimentation behaviour has remained unaltered. Upon reelectrophoresis, no new peaks are detectable although the relative proportions of the various subclasses are frequently changed. The ratio in the occurrence of these subclasses is readily affected by a variety of factors, however, some of which are not directly related to the electrophoretic technique itself.The three classes of ribosomes and subunits (70‐S, 50‐S and 30‐S) display approximately equal electrophoretic mobilities when the sieving action is reduced to a minimum. This conclusion follows from experiments in which the ribosomes are submitted to electrophoresis in a sucrose gradient or in 0.4% agarose gels. In contrast, electrophoresis in polyacrylamide gels with a gradient in pore size reveals the same ribosomal diversity as noted in gels with a fixed acrylamide concentration of 4%. In these pore‐gradient gels (3‐8% acrylamide), the migration rate of each ribosomal subclass decreases continuosly when the time of electrophoresis is prolonged. After about 30 h, further penetration seems to be blocked.All three classes consist of particles with low electrophoretic mobility (designated I particles) and those which move faster (designated II particles). The I particles are partially converted to II particles by incubation at 37 °C and/or pelleting prior to electrophoresis. The II particles are converted to I particles upon raising the ribosome concentration. The electrophoretic profiles displayed by the various 50‐S subclasses are not strongly affected by variations in Mg2+ concentration in the range 0.5‐10.0 mM. The electropherograms of 30‐S subunits become more diffuse when the Mg2+ concentration is raised. The possible occurrence of ribosomal dimers and/or conformation changes is discussed.

Observations of self-aggregation and dissociation of E. coli ribosomes by optical mixing spectroscopy.

AbstractMeasurements of the diffusion coefficient of E. coli ribosomes by the technique of optical mixing spectroscopy are used to show that these ribosomes, when incubated in a 4°C cold room, undergo a slow aggregation with time. Even in the presence of this aggregation, it was possible to observe the diffusive character of the single 70s ribosome. It was found that at high (≥0.100 molar) KCl concentrations the ribosomes broke into their subunits. At moderate KCl concentrations they were relatively stable and at a very low KCl concentration (0.005 M) they were observed to dimerize. The values of the diffusion coefficients of the 50s subunits, the 70s single ribosome and the ribosome dimer determined in these measurements are consistent with currently accepted values.

Formation of ribosome dimers in brains of hypothermic rats

Summary Hypothermia, induced in rats, caused marked disaggregation of brain polysomes. The disaggregation was reflected primarily as an increase in the dimer peak and was accompanied by a reduced capacity for amino acid incorporation in vitro , by post-mitochondrial fractions. The disaggregation ,as well as the changes in amino acid incorporation ability caused by hypothermia, were reversible, inasmuch as brains of hypothermic rats brought back to normal temperatures before sacrifice had polysome profiles similar to those of control animals. The changes in polysome patterns due to hypothermia could not be observed if the animals were treated with cycloheximide before induction of hypothermia.

On the function and fate of phage progeny RNA in infected bacteria.

ABSTRACT Spheroplasts of Escherichia coli infected with RNA phage R17 were treated with actinomycin D to inhibit the synthesis of host RNA and protein. Ribosomes occurred predominantly as monomers, dimers and trimers which were active in viral protein synthesis. Partly finished strands of viral RNA in lysates sedimented at a rate characteristic of groups of 6–12 ribosomes and their buoyant density suggested that they were in fact attached to ribosomes. Newly completed strands were associated with single (70-s) ribosomes, forming a 75-S complex, and with ribosome dimers and trimers. Some were probably loosely bound to 30-s ribosomal subunits. Newly made RNA began to accumulate in mature virions after a lag of about 5 min and rose to 16 % of the total labelled viral RNA by the end of the growth cycle, either with continuous labelling or after a 5-min pulse followed by a non-radioactive chase. It is suggested that most, if not all, new viral RNA forms a rather stable association with ribosomes and that a small proportion of this RNA may subsequently pass into progeny virus.

Increased yield of ribosome dimers from the rat seminal vesicle following castration

FEBS LettersVolume 8, Issue 6 p. 337-340 Full-length articleFree Access Increased yield of ribosome dimers from the rat seminal vesicle following castration M. Tóth, M. Tóth Institute of Medical Chemistry, Semmelweis University Medical School. Budapest, HungarySearch for more papers by this author M. Tóth, M. Tóth Institute of Medical Chemistry, Semmelweis University Medical School. Budapest, HungarySearch for more papers by this author First published: July 03, 1970 https://doi.org/10.1016/0014-5793(90)80008-7Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References 1 R.W. Reader, C.P. Stanners, J. Mol. Biol., 28, (1967), 211– 2 M. Tóth, Acta Biol. Acad. Sci. Hung., 19, (1968), 519– 3 G. Blobel, V.R. Potter, J. Mol. Biol., 26, (1967), 279– 4 M. Tóth, R. Machovich, Acta Biochim. Biophys. Acad. Sci. Hung., 4, (1969), 339– 5 M. Tóth, S. Mányai, Acta Biochim. Biophys. Acad. Sci. Hung., 3, (1968), 29– 6 S. Liao, R.W. Barton, A.H. Lin, Proc. Natl. Acad. Sci. U.S., 55, (1966), 1593– 7 S. Liao, A.H. Lin, R.W. Barton, J. Biol. Chem., 241, (1966), 3869– 8 S. Liao, A.H. Lin, Proc. Natl. Acad. Sci. U.S., 57, (1967), 379– 9 S. Liao, H.G. Williams-Ashman, Proc. Natl. Acad. Sci. U.S., 48, (1962), 1956– 10 D.A. Silverman, S. Liao, H.G. Williams-Ashman, Nature, 199, (1963), 808– 11 S. Liao, J. Biol. Chem., 240, (1965), 1236– 12 W.D. Wicks, D.L. Greenman, F.T. Kenney, J. Biol. Chem., 240, (1965), 4414– 13 D.L. Greenman, W.D. Wicks, F.T. Kenney, J. Biol. Chem., 240, (1965), 4420– Citing Literature Volume8, Issue6July 03, 1970Pages 337-340 ReferencesRelatedInformation

Human leukemic polyribosomes.

SummaryRibosomes were prepared from normal human granulocytes, acute and chronic leukemias and rat liver. These preparations were analyzed for polyribosome (PRS) profile by means of sucrose density gradient centrifugation. None of the leukemic cell preparations had as high a proportion of PRS as did rat liver. Normal granulocytes and chronic granulocytic leukemic (CGL) cells had a greater fraction of PRS than did acute granulocytic (AGL) or chronic lymphocytic leukemic (CLL) cells. Most of the AGL and CLL particles were ribosomal subunits, monomer s, and dimers. With 30′ of uridine-3H labeling of all types of leukemic cells, the highest specific activity was in the subunits and PRS regions with low specific activity in the monomer-dimer regions. The data suggests that the monomers and dimers are not intermediates for the formation of PRS.

On the significance of ribosome dimers in extracts of animal cells

Virtually all of the free ribosomes in cytoplasmic extracts of hamster cells were found to be in the dimer configuration under conditions of extraction which gave an optimum yield of stable polysomes. Evidence is presented for the view that most of the free ribosomes are not dimers within the cells, but form dimers during the extraction procedure by Mg2+ -dependent and temperature-dependent bonds. Ribosomes obtained by mild RNase digestion of polysomes did not dimerize under the same conditions. To assess the biological significance of the dimerization of ribosomes, cytoplasmic extracts from several mammalian species were examined, using embryonic, differentiated and malignant cells from each species. The dimerization phenomenon was dramatically species-dependent and showed no correlation with the other biological determinants: hamster and rat ribosomes could dimerize, mouse, groundhog and human ribosomes could not.

The possible role of sulfhydryl groups in the dimerization of 70S ribosomes from Escherichia coli

The possible role of sulfhydryl groups in the dimerization of 70S ribosomes from Escherichia coli

The Inhibition of Rat Liver Polyribosome Breakdown in the Presence of Liver Supernatant

Abstract Rat liver ribosomes prepared from the rapidly sedimenting pellet of a liver homogenate or from the microsomal pellet by the treatment of these pellets with sodium deoxycholate in buffer are deficient in polyribosomes and contain primarily ribosome dimers. Dimer formation can be prevented and a good polyribosome pattern can be obtained from both these pellets provided treatment with sodium deoxycholate takes place in the presence of liver supernatant. It has been shown that the polyribosomes isolated from the rapidly sedimenting pellet incorporate glycine into acid-insoluble material in vivo and are broken down into single ribosomes and ribosome dimers by ribonuclease.