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PubMedDate not supplied

[Peptidyltransferase center of ribosomes. II. Effect of temperature on the activity of model peptide donors and a study of oligopeptide formation in a matrix-free system with ribosomes].

The reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate with Phe-tRNA or CACCA-Phe catalysed with E. coli MRE-600 ribosomes and stimulated with cytidine 5'-phosphate was investigated. It was shown that the reaction with Phe-tRNA was stimulated within 2--3 times when the temperature has been raised from 0 to 40 degrees. On the contrary when the peptide acceptor was CACCA-Phe the yield of peptides synthesis dropped 5 times and more under the same conditions. Similar temperature influence was observed in the reaction with 50S subunits. The inhibition of peptide bond formation with pA and CpA at 0 degrees was achieved up to 80--90% but it was very low at 40 degrees. The synthesis of tri- and tetrapeptides was observed when the reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate was carried out either with Phe-tRNA or with CACCA-Phe.

Acyltransferases↗
PubMed1978

Isolation of eukaryotic ribosomal proteins. Purification and characterization of the 60 S ribosomal subunit proteins La, Lb, Lf, P1, P2, L13', L14, L18', L20, and L38.

The proteins of the large subunit of rat liver ribosomes were separated into seven groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Ten proteins (La, Lb, Lf, P1, P2, L13', L14, L18', L20, and L38) were isolated from three groups (A60, B60, and D60) by ion exchange chromatography on carboxymethylcellulose and DEAE-cellulose, and by filtration through Sephadex. The amount of protein obtained varied from 0.3 to 3.8 mg. Two of the proteins (La and L18') had no detectable contamination; the impurities in the others were not greater than 8%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined. Several additional acidic proteins were identified: P1a and P1b are phosphorylated derivatives of P1; P2a, P2b, and P2c are phosphorylated derivatives of P2. P1 and P2 are distinct proteins but both have large amounts of alanine (20.4 and 17.5 mol %).

Amino Acids↗
PubMed1980

Euglena gracilis chloroplast ribosomal RNA transcription units. I. The location of transfer RNA, 5 S, 16 S, and 23 S ribosomal RNA genes.

The organization of the genes in the rRNA coding region of Euglene gracilis Pringsheim strain Z chloroplast DNA has been determined. 125I labeled 16 S rRNA, 125I labeled 23 S rRNA, and [32P]tRNAs were hybridized to restriction nuclease fragments from cloned chloroplast DNA segments. The coding regions for 16 S and 23 S rRNAs have been located to within 1.75 and 3.1 kbp, respectively. Transfer rRNA genes are located in the 16 S to 23 S rRNA spacer region. Ribosomal RNAs and tRNAs are encoded on the same DNA strand in the 6.2 kbp tandemly repeated rRNA gene region. The order of genes, which is repeated three times in chloroplast DNA, is 16 S rRNA--tRNAS--23 S rRNA--5 S rRNA. Each set of genes is clustered in a region of 5.0 kbp. The organization and size of the genes is as expected if they are all part of a single transcription unit.

Chloroplasts↗
PubMed1982

Structure of the Syrian hamster ribosomal DNA repeat and identification of homologous and nonhomologous regions shared by human and hamster ribosomal DNAs.

We have cloned and partially characterized Bam HI fragments of Syrian hamster DNA containing most of the ribosomal RNA-coding region. Several restriction site polymorphisms within the transcribed portions of the hamster rDNA repeats have been noted. Approximately three-fifths of the repeats contain a Bam HI site upstream of the 18 S coding sequences. Approximately four-fifths of the repeats contain a Bam HI site very close to the 5' end of the 28 S coding sequences. This microheterogeneity has been maintained in the DNA of baby hamster kidney (BHK)-21 cells, a cell line established nearly 20 years ago. R-loop analysis with homologous hamster rRNAs has established the size of the coding regions and the internal transcribed spacer. Heterologous R-loop analyses with cloned hamster rDNAs and human rRNAs reveal several well-defined regions within the 28 S gene where the homology between human and hamster RNAs is greatly reduced. These regions are not detectable in heteroduplexes of hamster and human rDNAs. Sequences encoding the 18 S gene do not exhibit such reduced homology.

Animals↗
PubMed1983

Identification of the 3'-ends of the two mouse mitochondrial ribosomal RNAs. The 3'-end of 16 S ribosomal RNA contains nucleotides encoded by the gene for transfer RNALeuUUR.

The 3'-termini of the mitochondrial 12 S and 16 S ribosomal RNAs from mouse L cells have been definitively characterized by mobility-shift RNA sequencing, RNase digestion followed by fingerprinting using two-dimensional homochromatography, and precise mapping of RNA-DNA duplexes using nuclease S1. The results have been correlated with the known DNA sequence of the rRNA region. The vast majority of the 12 S rRNA consists of a family of transcripts whose last template-encoded nucleotide corresponds to a position immediately adjacent to the 5' end of the tRNAVal gene in the DNA sequence. These transcripts are oligoadenylated at their 3'-ends with from 1 to about 5 adenylate residues that are not encoded in the DNA sequence. A minor proportion of the 12 S rRNA ends one nucleotide before the 12 S/tRNAVal gene boundary and is also oligoadenylated. In contrast, the 3'-termini of 16 S rRNA have considerably greater heterogeneity, with the genomic location of the last template-encoded nucleotide varying from the nucleotide immediately adjacent to the 5'-end of the tRNALeuUUR gene to any position up to 7 nucleotides downstream within the tRNALeuUUR gene sequence. These various 16 S rRNA transcripts are oligoadenylated to a somewhat greater degree than the 12 S rRNA. The extent of the 16 S rRNA 3' heterogeneity, as compared to the 12 S rRNA, suggests that the 16 S rRNA 3'-termini may be generated by a mechanism involving termination of transcription rather than by processing of a primary transcript. The data are similar to those reported for human mitochondrial rRNA 3'-termini, and support a general role for adenylation of 3'-termini in the termination or processing of mammalian mitochondrial RNAs.

Animals↗
PubMedDate not supplied

[Mechanism of codon-anticodon interaction in ribosomes. Interaction of aminoacyl-tRNA with 70S ribosomes in the absence of elongation factor EF-Tu and GTP].

Purified Phe-tRNAPhe revealed higher affinity to the donor (D) site of vacant 70S . poly(U) complex than to the acceptor (A) site, independent on Mg2+ concentration. As a result, in excess of ribosomes Phe-tRNAPhe binds exclusively to the D site. This was proved using the tests in the presence of tetracycline and puromycin. Preferential binding of Phe-tRNAPhe to the D site was used to measure equilibrium association constants of this interaction at different temperatures and Mg2+ concentrations. A large value of reaction enthalpy (ca. -26 Kcal/mole) was found.

Anticodon↗
PubMed1978

Studies on proteins of animal ribosomes. XXVIII. Preparation and antigenic properties of 40 S subunit proteins of rat liver ribosomes.

By combination of ion exchange chromatography, gel filtration, preparative polyacrylamide gel electrophoresis and perchloric acid fractionation 21 proteins of the small ribosomal subunit of rat liver were isolated with a purity of more than 95%. It could be demonstrated by immunological studies that no extensive structural homologies exist between these proteins.

Animals↗
PubMed1995

Structural and functional studies of retroviral RNA pseudoknots involved in ribosomal frameshifting: nucleotides at the junction of the two stems are important for efficient ribosomal frameshifting.

Ribosomal frameshifting, a translational mechanism used during retroviral replication, involves a directed change in reading frame at a specific site at a defined frequency. Such programmed frameshifting at the mouse mammary tumor virus (MMTV) gag-pro shift site requires two mRNA signals: a heptanucleotide shifty sequence and a pseudoknot structure positioned downstream. Using in vitro translation assays and enzymatic and chemical probes for RNA structure, we have defined features of the pseudoknot that promote efficient frameshifting. Heterologous RNA structures, e.g. a hairpin, a tRNA or a synthetic pseudoknot, substituted downstream of the shifty site fail to promote frameshifting, suggesting that specific features of the MMTV pseudoknot are important for function. Site-directed mutations of the MMTV pseudoknot indicate that the pseudoknot junction, including an unpaired adenine nucleotide between the two stems, provides a specific structural determinant for efficient frameshifting. Pseudoknots derived from other retroviruses (i.e. the feline immunodeficiency virus and the simian retrovirus type 1) also promote frameshifting at the MMTV gag-pro shift site, dependent on the same structure at the junction of the two stems.

Animals↗
PubMed1977

Isolation of eukaryotic ribosomal proteins. Purification and characterization of 60 S ribosomal subunit proteins L3, L6, L7', L8, L10, L15, L17, L18, L19, L23', L25, L27', L28, L29, L31, L32, L34, L35, L36, L36', and L37'.

The proteins of the large subunit of rat liver ribosomes were separated into seven groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Twenty-one proteins (L3, L6, L7', L8, L10, L15, L17, L18, L19, L23', L25, L27', L28, L29, L31, L32, L34, L35, L36, L36', and L37') were isolated from three groups (C60, E60, and F60) by ion exchange chromatography on carboxymethycellulose and by filtration through Sephadex. The amount of protein obtained varied from 0.3 to 25 mg. Nine of the proteins (L6, L8, L18, L27', L28, L29, L34, L36, and L36') had no detectable contamination: the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1977

Isolation of eukaryotic ribosomal proteins. Purification and characterization of the 40 S ribosomal subunit proteins Sa, Sc, S3a, S3b, S5', S9, S10, S11, S12, S14, S15, S15', S16, S17, S18, S19, S20, S21, S26, S27', and S29.

The proteins of the small subunit of rat liver ribosomes were separated into five main groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Twenty-one proteins (Sa, Sc, S3a, S3b, S5', S9, S10, S11, S12, S14, S15, S15', S16, S17, S18, S19, S20, S21, S26, S27', and S29) were isolated from three groups (A40, C40, and D40) by ion exchange chromatography on DEAE-cellulose, carboxymethylcellulose, and phosphocellulose and by filtration through Sephadex. The amount of protein obtained varied from 0.1 to 11 mg. Six of the proteins (S5', S10, S11, S18, S19, and S27') had no detectable contamination; the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1976

The isolation of eukaryotic ribosomal proteins. The purification and characterization of the 40 S ribosomal subunit proteins S2, S3, S4, S5, S6, S7, S8, S9, S13, S23/S24, S27, and S28.

The proteins of the small subunit of rat liver ribosomes were separated into five groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5 (Collatz, E., Lin, A., Stöffler, G., Tsurugi, K., and Wool, I.G., (1976) J. Biol. Chem. 251, 1808-1816). From the several groups, 12 proteins (S2,S3, S4, S5, S6, S7, S8, S9, S13, S23/S24, S27, and S28) wereisolated by ion exchange chromatography on carboxymethylcellulose, by chromatography on sulfopropyl-Sephadex, and by gel filtration through Sephadex G-75. The amount of protein obtained varied from 1 to 9 mg depending on the number of steps required for the preparation; several proteins had no detectable contamination and the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyazrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1976

Ionic interactions in eukaryotic ribosomes: splitting of the subunits of rat liver ribosomes by treatment with monovalent cations.

Proteins of rat liver ribosomal subunits were successively split off by stepwise treatment of the particles with various concentrations of LiC1 (0.4--1.0 M) or KC1 (0.6--1.5 M). Split proteins and core particle proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. The LiC1 concentrations were estimated at which the individual proteins are split off. The proteins of 40S and 60S subunits were classified in 4 and 5 groups, respectively, according to their splitting behavior. The effect of LiC1 and KC1 is similar, but higher concentrations of KC1 than of LiC1 are required to obtain comparable split protein patterns. Evidence for structural changes of the core particles during the split procedures was obtained.

Animals↗
PubMed1992

The 23S/5S ribosomal RNA genes (rrl/rrf) are separate from the 16S ribosomal RNA gene (rrs) in Borrelia burgdorferi, the aetiological agent of Lyme disease.

DNA fragments containing the rRNA genes for Borrelia burgdorferi strain B31 were cloned in bacteriophage lambda EMBL3. A restriction map of the fragments was constructed and the organization of the rRNA genes was determined by Southern hybridization. One genomic DNA fragment contained a single copy of the rrs sequence and another cloned fragment contained both rrl and rrf sequences. The results revealed that the rrs gene is located separately from the set of rrl/rrf genes, suggesting that these rRNA genes are expressed independently in B. burgdorferi.

Blotting, Southern↗
PubMed1981

Membrane-bound ribosomes of myeloma cells. VI. Initiation of immunoglobulin mRNA translation occurs on free ribosomes.

Immunoglobulin heavy (Ig H) and light (Ig L) chain mRNA molecules have been released from the endoplasmic reticulum (ER) membranes as free (F) mRNP particles when MOPC 21 (P3K) mouse myeloma cells are exposed to a hypertonic initiation block (HIB). The subsequent fate of these mRNA sequences has been examined when the cells are returned to normal growth medium. Upon return to isotonicity, all previously translated mRNA molecules reassociate with ribosomes and form functional polysomes. Ig H mRNA is found incorporated first into F polysomes and then into membrane-bound (MB) polysomes. Kinetic studies indicate that the time of passage of Ig H mRNA in F polysomes is approximately 30 s, during which a nascent polypeptide chain of approximately 80 amino acids would have been completed. When the rate of polypeptide elongation is depressed with emetine during the recovery from HIB, both Ig H and L mRNA molecules accumulate in small F polysomes. These results indicate that the formation of Ig-synthesizing polysomes proceeds in the sequence: mRNA leads to F polysomes leads to MB polysomes. With the additional observation that during HIB recovery puromycin completely prevents the reassociation of Ig mRNA with the ER, these findings support a model of MB polysome formation in which the specificity of membrane attachment is determined by the nature of the N-terminal amino acid sequence of the nascent polypeptide chain.

Animals↗