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Biomedical subjects

H Bielka

Publications and source records attributed to H Bielka.

At least 55 records · Page 3Linked to original sources
PubMed1982

Structure of IgG and IgY molecules in ribosome-antibody complexes as studied by electron microscopy.

The overall shape and dimensions of IgG (rabbit) and IgY (chicken) antibodies against ribosomal proteins have been studied in electron micrographs of ribosome-antibody complexes. The antibodies appear as Y-shaped molecules with an angle of about 90 degrees between their Fab arms. The length of one Fab arm amounts to about 10 nm. No differences between the IgG and IgY molecules could be detected electron microscopically. The data obtained on the shape of IgG and IgY correlate with those of earlier electron microscopic studies while the determined size of the Fab arms is in the range found by scattering methods.

Animals↗
PubMed1982

Preparation of spin-labeled poly(U) and its activity in assays with eukaryotic ribosomes.

ESR studies on the interaction of spin-labeled polynucleotides with ribosomes require a sufficient label-to-nucleotide ratio. Using three different spin labels (SL) we have elaborated a technique to label poly(U) up to a ratio of 1 SL per 30 uridine residues. This ratio is much higher than maximal values obtained by other authors. The SL-poly(U) was shown to have the same activity as unlabeled poly(U) to direct synthesis of poly(Phe). SL-poly(U) binds to rat liver ribosomes in the presence of Mg2+ as shown by ESR. Titration with EDTA leads to a release of SL-poly(U) from ribosomes.

Animals↗
PubMed1982

The toxic A-chain of mistletoe lectin I: isolation and its effect on cell-free protein synthesis.

The reduction of Sepharose bound mistletoe lectin I (ML I) is a convenient method for preparing A- and B-chains under mild conditions. The B-chain represents the D-galactose binding moiety. The A-chain shows a significant dose-dependent inhibition of protein synthesis in cell-free systems from rat liver and rabbit reticulocytes, while pure B-chain preparations do not affect ribosomal translation processes.

Animals↗
PubMed1981

A small-angle and wide-angle x-ray scattering study of the shape and secondary structure of native 5 S RNA from rat liver ribosomes.

Native 5 S RNA from rat liver ribosomes was investigated by means of small-angle and wide-angle X-ray scattering. The radius of gyration, Rs of the molecule is 3.1 nm, the maximum dimension, L, 10.5 nm and the shape volume, Vc, about 60 nm3. The overall shape of the molecule as derived from these parameters is a flat elliptical cylinder with dimensions of 2a = 10.45 nm, 2b = 6.94 nm, H = 1.06 nm. The cross-section radius of gyration of 0.92 nm and the mass per unit length of 2610 mol X nm-1 of the 5 S RNA molecule are typical for a double helical organized RNA molecule. From wide-angle scattering data it can be concluded that the double helical regions are in the A-form characterized by an 11-fold helix with a turn angle of 32.7 degrees and a distance of 0.28 nm between adjacent base pairs. A refined electron density model of a distorted L shape is proposed for the 5 S RNA molecule.

Animals↗
PubMed1981

Cross-linking of Met-tRNAf to eIF-2 beta and to the ribosomal proteins S3a and S6 within the eukaryotic inhibition complex, eIF-2 .GMPPCP.Met-tRNAf.small ribosomal subunit.

In the quaternary initiation complex, eIF-2.GMPPCP.Met-tRNAf.40S ribosomal subunit, the Met-tRNAf can be cross-linked to the beta subunit of initiation factor eIF-2 as well as to ribosomal proteins S3a and S6 by treatment with the bifunctional reagent, diepoxybutane. Using 40S subunits, modified in advance with the heterobifunctional reagent, methyl-rho-azido-benzoylaminoacetimidate, Met-tRNAf is covalently bound to the same ribosomal proteins (S3a and S6) upon irradiation of the complex with ultraviolet light. Under both conditions proteins S3a and S6, together with a limited number of other ribosomal proteins, are covalently bound to 18S ribosomal RNA.

Cross-Linking Reagents↗
PubMed1981

Phosphorylation of ribosomal proteins as a possible control system for protein synthesis. Binding of Met-tRNAf to 40 S ribosomal subunits.

The evidence that protein S6 of rat liver ribosomes is involved in P-site functions and that this protein is the main target of the small subunit for in vivo phosphorylation suggests that S6 phosphorylation may contribute to the regulation of protein synthesis. Therefore, we have studied the activity of small ribosomal subunits with unphosphorylated and phosphorylated protein S6 in Met-tRNAf binding. The results described in this paper show that at least under in vitro conditions S6 phosphorylation does obviously not influence the activity of small ribosomal subunits for eIF-2 dependent binding of initiator-tRNA.

Animals↗
PubMed1980

The alpha and gamma subunits of initiation factor eIF-2 can be cross-linked to 18S ribosomal RNA within the quaternary initiation complex, eIF-2.Met-tRNAf.GDPCP.small ribosomal subunit.

Initiation factor eIF-2 from rat liver was reacted with the hetero-bifunctional cross-linking reagents ABAI or APTPI without diminishing its ability to form the quaternary initiation complex with Met-tRNAf, GDPCP and the small ribosomal subunit. Upon irradiation with UV light, subunits alpha and gamma of eIF-2 became covalently linked to 18S ribosomal RNA. The subunits were identified electrophoretically after isolation of the covalent protein-rRNA complexes and subsequent degradation of the rRNA by nuclease and alkali treatments. The close proximity of the two factor subunits to sequences of ribosomal RNA within the quaternary complex could be confirmed in a second set of experiments using unmodified, 125I-labeled factor and diepoxybutane as cross-linking reagent.

Animals↗
PubMed1980

[The analysis of localization and function of proteins in eukaryotic ribosomes by means of antibodies (author's transl)].

Due to their high specificity antibodies reveal possibilities for a detailed analysis of structure and function of eukaryotic ribosomes. By means of specific antibodies against single ribosomal proteins we could (1) localize immunoelectron microscopically certain proteins at the surface of ribosomes and (2) determine their role within protein biosynthesis by the binding of the initiation factor eIF-2 to the small ribosomal subunit. The combination of the results of both methods provides evidence of the localization of the peptidyl-tRNA binding site in the head area of the small subunit of ribosomes.

Animals↗
PubMed1980

Neighbourhoods of proteins S2--S3, S3--S3a, S15--S15a, and S5--S25 within the small subunit of rat liver ribosomes.

Cross-linking of proteins within the small subunit of rat liver ribosomes by the bifunctional reagent dimethyl 3.8-diaza-4.7-dioxo-5.6-dihydroxydecanbisimidate results in the formation of various complex which were separated by two-dimensional polyacrylamide gel electrophoresis. Components of four complexes were electrophoretically identified after periodate cleavage as S2--S3, S3--S3a, S15--S15a, and S5--S25.

Animals↗
PubMed1980

Physicochemical studies of the 7 S complex of rat liver ribosomes and its components.

The 7 S complex of rat liver ribosomes contains 5 S RNA and one protein (L-5). The molecular weights of these two components are 40 600 and 37 200, respectively, as estimated by analytical ultracentrifugation. Th complex stability under different solvent conditions was analyzed from the point molecular weights using a sedimentation equilibrium technique and computer stimulation. High concentrations of KCl and urea induce partial dissociation, whereas MgCl stabilizes the complex.

Animals↗
PubMed1980

Effect of preincubation in the cold on poly(U)-dependent polyphenylalanine synthesis in a cell-free rat liver system.

Preincubation of a cell-free poly(Phe) synthesis system in the cold results in a manifold stimulation of the polyphenylalanine synthesis. This stimulatory effect can be observed only if ribosomal subunits, poly(U), Mg++ and cytosolic fraction are present in the reaction mixture during cold pretreatment. This effect is abolished if the samples are preincubated at 37 degrees C before the cold treatment probably because of an inactivation of protein factors present in the cytosolic fraction.

Animals↗
PubMed1979

Localization of proteins S1, S2, S16 and S23 on the surface of small subunits of rat liver ribosomes by immune electron microscopy.

Ribosomal proteins S1, S2, S16 and S23 were localized on the surface of the small subunit (40S) of rat liver ribosomes by immune electron microscopy. Antibodies against the single proteins were raised in rabbits and chicken and purified by affinity chromatography. 40S-IgG-40S complexes were obtained by incubation of 40S subunits with non-cross-reacting antibodies specific for each of the four proteins and subsequent sucrose density gradient centrifugation. The location of the proteins was determined by means of antibody binding sites visualized in negative contrast in the electron microscope. The four investigated proteins are mainly located in the head region of the small subunit. Exposed antigenic determinants of proteins S1 and S2 were found to be located at different sites of the small subunit whereas proteins S16 and S23 were mapped in a limited region only.

Animals↗