25 research outputs found

    Active sites in Escherichia coli ribosomes

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    AbstractIn the figure, 30 S ribosomal proteins have been arranged according to their functional role: Protein S1 is required for mRNA binding. Proteins S3, S4, S5, S11 and S12 are involved in cistron and/or codon—anticodon recognition. They must be close to the decoding sites on the 30 S subunit. Furthermore proteins S2, S3, S10, S14, S19 and S21 function in f-Met-tRNA binding. Proteins S1, S2, S3, S10, S14, S19, S20 and S21 are important for the function of both decoding sites, whereas proteins S9, S11 and S18 are only needed for EF—Tu-dependent aminoacyl-tRNA binding. Proteins S2, S5, S9 and S11 would be close to the GTPase center of the 50 S subunit, since they are important for this activity.The present available data concerning the 50 S subunit allow the following picture to be drawn: Protein L16 is involved in binding the 3′-terminus of aminoacyl-tRNA in the A-site. Next to it in the A-site, there is protein L6. The P-site is located adjacent to the A-site of the peptidyltransferase center. Accordingly, protein L2 is near protein L6 and is located in the P-site as well as proteins L27 and L4. Protein L11, which is intimately involved in peptide bond formation, would have to border parts of both A- and P-sites. Proteins L6 and L2 stimulate binding of 5 S RNA—protein complexes to 23 S RNA. The 5 S RNA—protein complex has GTPase and ATPase activities. The proteins in this complex (L5, L18, L20, L25 and L30) seem to be located close to the A-site of the peptidyltransferase center. These proteins together with protein L11 are involved in GDP binding. Proteins L10 and L6 are implicated in reconstitution of protein L7 and L12 mediated EF—G-dependent ribosomal GTP hydrolysis. This observation is supported by the fact that the aminoacyl-tRNA binding site, e.g. proteins L16 and L6, is connected with EF—G and EF—Tu binding site, e.g. proteins L7 and L12, as well as the GTPase center. Furthermore, if one of the functional roles of 5 S RNA is to bind aminoacyl-tRNA via T—Ψ—C, then those ribosomal proteins which bind to 5 S RNA (or are close to it) would be located near or at the A-site.The model of active sites in E. coli ribosome illustrated in the figure is based on the presently available experimental results. It is far from being complete and should not be overinterpreted as an accurate topographical model. More data on the functional role of ribosomal components and on the topography of the subunits can be expected in the near future and will add to the knowledge on the active sites in ribosomes

    Ribosome assembly

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    This chapter contains sections titled: Assembly Of The Prokaryotic Ribosome Introduction Processing of rRNAs Precursor Particles and Reconstitution Intermediates Assembly-initiator Proteins Proteins Essential for the Early Assembly: The Assembly Gradient Late-assembly Components Proteins Solely Involved in Assembly Assembly Maps References Eukaryotic Ribosome Synthesis Introduction Prelude Why so many RRPs? (Pre-)ribosome Assembly, the Proteomic Era Ribosomal RNA Processing, Getting there. Ribosomal RNA Modification: A Solved Issue? Ribose Methylation, Pseudouridines formation and the snoRNAs The Emergence of the snoRNAs Non-ribosomal RNA Substrates for the snoRNAs Possible function(s) of RNA modifications Base methylation U3 snoRNP, the 'SSU Processome', and the Central Pseudoknot SnoRNA Synthesis and Intranuclear Trafficking SnoRNAs Synthesis Non-core snoRNP Proteins required for snoRNA Accumulation Interactions between Cleavage Factors and Core snoRNP Proteins SnoRNAs Trafficking CB/NB are Conserved Sites of Small RNP Synthesis Ribosome Intranuclear Movements and Ribosome Export The Cytoplasmic Phase of Ribosome Maturation Regulatory Mechanisms, all along And Now .What's Next? Epilogue Useful WWW links ReferencesSCOPUS: ch.binfo:eu-repo/semantics/publishe

    Aufstellen eines ersten Funktionsmodells des Ribosoms von Escherichia coli mit Hilfe der Neutronenstreuung (Protonenspin-Kontrastvariation) Schlussbericht

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    Available from TIB Hannover: DtF QN1(38,3) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

    Solution scattering structural analysis of the 70 S Escherichia coli ribosome by contrast variation .1. Invariants and validation of electron microscopy models

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    Solutions of selectively deuterated 70 S Escherichia coli ribosomes and of free 30 S and 50 S subunits were studied by neutron scattering using contrast variation. The integrity of the partially deuterated particles was controlled by parallel X-ray measurements. Integral parameters of the entire ribosome, of its subunits and of the protein and rRNA moieties were evaluated. The data allow an experimental validation of the two most recent electron microscopy reconstructions of the 70 S ribosome presented by the groups of J. Frank (Albany) and of M. van Heel & R. Brimacombe (Berlin). For each reconstruction, integral parameters and theoretical scattering curves from the 70 S and its subunits were calculated and compared with the experimental data. Although neither of the two models yields a comprehensive agreement with the experimental data, Frank’s model provides a better fit. For the 50 S subunit of van Heel & Brimacombe’s model the fit with the experimental data improves significantly when the internal channels and tunnels are filled up. The poorer fit of the latter model is thus caused by its “sponge”-like structure which may partly be due to an enhancement of high frequency contributions in some of the steps of the three-dimensional image reconstruction. It seems therefore unlikely that the ribosome has a “sponge”-like structure with a pronounced network of channels
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