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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Under specific conditions cycloheximide treatment of Saccharomyces cerevisiae caused the accumulation of a type of polyribosome called "halfmer." Limited ribonuclease digestion of halfmers released particles from the polyribosomes identified as 40S ribosomal subunits. The data demonstrated that halfmers are polyribosomes containing an additional 40S ribosomal subunit attached to the messenger ribonucleic acid. Protein gel electrophoretic analysis of halfmers revealed numerous nonribosomal proteins. Two of these proteins comigrate with subunits of yeast initiation factor eIF2.
Mol Cell Biol 1981 Jan
PMID:Characterization of a 40S ribosomal subunit complex in polyribosomes of Saccharomyces cerevisiae treated with cycloheximide. 676 95

To facilitate mapping of ribosomal protein genes in Bacillus subtilis, a selection was devised which gave rise to strains with alterations in any one of a variety or ribosomal proteins. Alterations in eighteen ribosomal proteins were identified when eighty mutants were analysed. In addition, one strain showed a major assembly defect in the large ribosomal subunit resulting in the presence of a particle sedimenting at about 40S. Eighteen large subunit proteins were present on this particle in normal amounts, while twelve proteins were much reduced in amount or undetectable.
Mol Gen Genet 1982
PMID:Selection in Bacillus subtilis giving rise to strains with mutational alterations in a variety of ribosomal proteins. 681 30

The ultrastructure of Drosophila melanogaster cytoplasmic ribosomal subunits and monomers have been examined by electron microscopy. The Drosophila ribosomal structures are compared to those determined for other eucaryotes and E. coli. Negatively contrasted images of 60S subunits are seen in the most frequent view to be approximately round particles about 280 A in diameter. About 35% of the particles present a single prominent projection which we call the 60S peak. The peak emanates from a flattened region of the 60S subunit. The maximum observed length of the 60S peak is approximately 90 A. The Drosophila 60S peak is highly reminiscent of the E. coli L7/L12 stalk. The Drosophila 40S subunit is an elongated, slightly bent particle which measures 280 X 170 X 160 A. It bears a strong resemblance to small ribosomal subunits of other eucaryotes and is strikingly similar to the E. coli 30S subunit. Micrographs of 80S monomeric ribosomes show the long axis of the 40S to be parallel and in apparent contact with the flattened region of 60S subunit. The 60S peak appears to bisect the long axis of the 40S subunit. The 40S subunit seems to be oriented in the monomeric ribosome so that the 40S projection is toward the body of the large subunit. Comparison of our data with similar studies in different organisms indicates that the eucaryotic large ribosomal subunits exhibit morphological heterogeneity while the small subunits remain remarkably similar.
Mol Gen Genet 1982
PMID:Structure of ribosomes and ribosomal subunits of Drosophila. 681 28

Four two-dimensional polyacrylamide gel electrophoresis systems were used to identify 78 Chinese hamster cell ribosomal proteins by the uniform nomenclature based on rat liver ribosomal proteins. The 40S ribosomal subunit protein affected by Chinese hamster ovary (CHO) cell one-step emetine resistance mutations is designated S14 in the standard nomenclature. To seek unambiguous genetic evidence for a cause and effect relationship between CHO cell emetine resistance and mutations in the S14 gene, we mutagenized a one-step CHO cell mutant and isolated second-step mutant clones resistant to 10-fold-higher concentrations of emetine. All of the highly resistant, two-step CHO cell mutants obtained displayed additional alterations in ribosomal protein S14. Hybridization complementation tests revealed that the two-step CHO cell emetine resistance mutants were members of the same complementation group defined by one-step CHO cell mutants, EmtB. Two-step mutants obtained from a Chinese hamster lung cell emetine-resistant clone belong to the EmtA complementation group. The two-step and EmtB mutants elaborated 40S ribosomal subunits, which dissociated to 32S and 40S core particles in buffers containing 0.5 M KCl at 4 degrees C. In contrast, 40S ribosomal subunits purified from all EmtA, one-step EmtB EmtC mutants, and wild-type CHO and lung cells were stable at this temperature in buffers containing substantially higher concentrations of salt. Thus, two-step emtB mutations affect the structure of S14 protein directly and the stability of the 40S ribosomal subunit indirectly.
Mol Cell Biol 1983 Feb
PMID:Ribosomal protein S14 is altered by two-step emetine resistance mutations in Chinese hamster cells. 683 9

Ribosomes from two different cell types of D. discoideum--the undifferentiated amoebae and the differentiated spores--display considerable differences in protein composition (Ramagopal and Ennis 1979 and manuscript in preparation). These differences do not affect the three-dimensional structure of monosomes and large (60S) and small (40S) subunits from the two cell types to an extent detectable by sedimentation analysis or electron microscopy. High resolution electron microscopic images of ribosomal particles from the amoebae and the spores are similar and, in general, comparable to that of 80S, 60S, and 40S ribosomal particles from other eukaryotic sources. However, distinct differences in the conformation and stability of the two types of ribosomes are detectable by circular dichroic spectroscopy. The degree of the ordered secondary structure of rRNAs is similar in the 80S monosomes from the amoebae and the spores, but higher in the amoeba subunits. The results of thermal melting experiments show that the small subunit from the spores is more stable than that from the amoebae. The established differences in the conformation of rRNAs, most probably due to the interactions with cell-specific ribosomal proteins, can be responsible for the differences in stability of ribosomes from the two cell types of slime mold.
Mol Gen Genet 1980
PMID:Conformation of ribosomes from the vegetative amoebae and spores of Dictyoistelium discoideum. 693 57

The cytoplasmic ribosomal proteins (r-proteins) of seventeen yeast species of the genera Saccharomyces and Kluyveromyces were analyzed by one-dimensional gradient polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The electrophoretic patterns of cytoplasmic r-proteins from different species display extensive differences in both the 40S and the 60S subunit. Relatedness of species suggested by r-protein patterns correlates well with that based on DNA/DNA homology (Bicknell and Douglas 1970). Immunochemical cross-reactions and antibiotic susceptibility tests were also used to compare different species. Analyses of r-proteins from two different interspecific hybrids showed that their ribosomes were hybrid, containing r-proteins from both parents. These findings are discussed in relation to the evolution of yeast species and the regulation of expression of r-proteins in eucaryotes.
Mol Gen Genet 1980
PMID:Studies of ribosomal proteins of yeast species and their hybrids: gel electrophoresis and immunochemical cross-reactions. 700 7

In Escherichia coli, a number of ribosomal proteins are methylated. The time of methylation of L7 and L11 during ribosome assembly was studied. It was observed that the methylation of L7 could occur in the free protein stage. Both the 32S and 40S ribonucleoprotein intermediates also contained methylated L7 although the extent of methylation in these particles was not as high as in the free L7, the 45S or the 50S particles. Free L11 could also be partially methylated but the bulk of methylation of this protein was found in the 45S and the 50S particles. It was previously reported that the methylation of L7 is inversely proportional to the growth temperature (Chang 1978), we now show that once L7 is methylated at 25 degree, the methyl group is stable when the culture is shifted to 37 degree C. However, a partial turnover of the methyl group of L7 is observed when the methylated ribosome is chased at 25 degree C. On the other hand, the methyl groups of L11 appear to be stable at either 25 degree C or 37 degree C. We also observe that the extent of methylation of both L7 and L11 stays nearly constant during the cell growth cycle from early log to stationary phase.
Mol Gen Genet 1981
PMID:Methylation of ribosomal proteins during ribosome assembly in Escherichia coli. 703 76

Fractions of reticulocyte lysates were retained on heparin immobilized on Sepharose 4B and further separated by gel filtration on Sepharose 6B. These fractions contain aminoacyl-tRNA synthetases for 12 amino acids tested. Most synthetases with the highest specific activity are present in the fraction of approximately 40S. Particulate synthetases present in the postmicrosomal pellet of rat liver and synthetases associated with polyribosomes are almost completely adsorbed on heparin-Sepharose but free enzymes in the cytosol are not retained. Since only particulate synthetases are retained on the affinity carrier, their adsorption may be due to the presence of protein-synthesis factors, in particular peptide initiation and elongation factors, in the complexes of synthetases.
Mol Biol Rep 1980 Dec 31
PMID:Particulate aminoacyl-tRNA synthetases are retained on heparin bound to Sepharose. 720 73

Rat liver 40S ribosomal subunits were treated with a bifunctional imidoester, dimethyl 3,3'-dithiobispropionimidate (DTP), and the neighboring protein pairs were identified. The cross-linked proteins were analyzed by acrylamide/SDS diagonal gel electrophoresis (Sommer & Traut (1974) Proc. Natl. Acad. Sci. U.S. 71, 3946-3950). The cross-linked components that fell off the diagonal upon adding 2-mercaptoethanol in the second dimension were labeled with 125I in the acrylamide gel and identified by two-dimensional acrylamide/urea gel electrophoresis, followed by radioautography. Considering these results and the molecular weights, we propose the following ten pairs, according to our numbering system (Terao & Ogata (1975) Biochim. Biophys. Acta 402, 219-229): S3-S5 (S3/S3a-S4), S3-S14 (S3/S3a-S14), S3-S17 (S3/S3a-S16), S5-S22 (S4-S23/S24), S10-S12 (S8-S11), S9-S16 (S9-S18), S9-S22 (S9-S23/S24), S6-S23 (S5-S25), S17-S21 (S16-S19), and S16-S26 (S18-S27). The designation according to the proposed uniform nomenclature (McConkey et al. (1979) Mol. Gen. Genet. 169, 1-6) are given in parentheses.
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PMID:Identification of neighboring protein pairs cross-linked with dimethyl 3,3'-dithiobispropionimidate in rat liver 40S ribosomal subunits. 728 76

The properties of the informosomes released from isolated nuclei of wheat embryos were studied in an in vitro system. The release of the informosomes from isolated nuclei of wheat embryos labelled with [3H]uridine is stimulated by exogeneous ATP. Optimal conditions for informosomes release from nuclei were determined. The particles obtained have heterogeneous sedimentation coefficients in sucrose gradient ranging from 10 to 60S. The particles are sensitive to low concentrations of RNase. Buoyant density in CsCl is 1.40-1.43 g/cm3. RNA extracted from particles is characterized by heterogeneous distribution in sucrose gradient between 4 and 20S. The informosomes contain two main peptides with molecular mass 36 000 and 51 000 and a number of minor peptides.
Mol Biol (Mosk)
PMID:[Release of informosomes from isolated nuclei of wheat embryos in an in vitro system]. 733 79


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