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排序方式: 共有157条查询结果,搜索用时 31 毫秒
1.
George John Acton 《Phytochemistry》1974,13(8):1303-1310
The light-dependent increment in RNase activity (which is ribosome bound in cell extracts) is distributed as a gradient increasing from base to hook of lupin hypocotyls. No evidence was found of non-specific or of specific activation of pre-formed enzyme molecules following isolation, either before or after (latent activity) destruction of particles. The autodegradation capacity of ribosomes isolated from irradiated cells was almost double that of ribosomes from etiolated tissue. It is proposed that association between the bulk of the light-controlled RNase fraction and lupin ribosomes results from binding of soluble protein. It is not clear whether binding is specific or an artifact of isolation. 相似文献
2.
We isolated a Zea mays cDNA encoding the 40S subunit cytoplasmic ribosomal protein S11. The nucleotide sequence was determined and the derived amino acid sequence compared to the corresponding Arabidopsis thaliana protein showing an homology of 90%. This ribosomal protein is encoded by a small multigene family of at least two members. The mRNA steady-state level is about one order of magnitude higher in rapidly growing parts of the plant such as the roots and shoots of seedlings compared to fully expanded leaf tissue. 相似文献
3.
Agnes Cseplö Thure Etzold Jeff Schell Peter H. Schreier 《Molecular & general genetics : MGG》1988,214(2):295-299
Summary Experiments designed to establish stable chloroplast transformation require selectable marker genes encoded by the chloroplast genome. The antibiotic lincomycin is a specific inhibitor of chloroplast ribosomal activity and is known to bind to the large ribosomal subunit. We have investigated a defined region of the chloroplast 23 S rRNA genes from four lincomycin resistant Nicotiana plumbaginifolia mutants and from wild-type N. plumbaginifolia. The mutants LR415, LR421 and LR446 have A to G transitions at positions equivalent to the nucleotides 2058 and 2059 in the Escherichia coli 23 S rRNA. The mutant, LR400, possesses a G to A transition at a position corresponding to nucleotide 2032 of the E. coli 23 S rRNA. 相似文献
4.
Gymnodinium aeruginosum has the usual fine structure of a dinoflagellate but does not seem to contain a well elaborated peduncle or a microtubular basket. Naked cells are surrounded by a single large amphiesmal vesicle. It houses an endosymbiont with typical blue-green cryptophycean chloroplasts (generally only one), cryptophycean starch grains in the periplastidal cytoplasm without a nucleomorph, and two membranes separating the periplastidal cytoplasm from the cryptophycean cytoplasm which contains mitochondria, ER, vesicles and ribosomes, but no eukaryotic nucleus. The endosymbiont is surrounded by a single membrane. Possible ways of the acquisition of the endosymbiont and the problem of the existence of ribosomes within a compartment without nucleus are discussed.Devoted to Prof. Dr.L. Geitler, the Nestor of phycology and endosymbiosis research, on the occasion of the 90th anniversary of his birthday. 相似文献
5.
Salt-tolerance in plants. I. Ions, compatible organic solutes and the stability of plant ribosomes 总被引:7,自引:4,他引:3
C. J. BRADY T. S. GIBSON† E. W. R. BARLOW‡ J. SPEIRS R. G. WYN JONES§ 《Plant, cell & environment》1984,7(8):571-578
Abstract Polysomes and ribosomes recovered from a number of plant species were tested for stability when incubated at 25°C in salt solutions in the absence of ATP and initiation factors. Stability was assessed by sucrose density gradient analysis. The stability was inversely proportional to salt concentrations above 125 mol m−3 KCl. Polysomes were less stable in the presence of Na+ than K+ salts, and were much less stable in Cl− than in acetate salts. Polysomes from Triticum aestivum. Hordeum vulgare, Capsicum annuum, Helianthus annuus. Pisum sativum, Atriplex nummularia, Beta vulgaris, Cladophora sp., Enteromorpha sp. and Corallina cuvieri were similarly sensitive to KCl. Polysomes from Ulva lactuca were more sensitive than the other species. Cytoplasmic and plastid polysomes from T. aestivum were similarly unstable in 500 mol m−3 KCl. Unprogrammed ribosomal subunit couples from T. aestivum, B. vulgaris and U. lactuca showed Mg2+-dependent conformational instability and dissociation in KCl. Slight differences in ribosomal stability were observed between species, but these were unrelated to the salt tolerances of the plants. The ‘compatible’ organic solutes, glycinebetaine and proline, failed to reduce ion-induced instability. Ribosome yield and polysome profiles were similar in leaves of B. vulgaris containing significantly different levels of both Na+ and Cl− after growth in media containing 50 or 200 mol m−3 NaCl. The results are consistent with the hypothesis that plants maintain a cytoplasmic solute environment that is compatible with ribosomal stability. 相似文献
6.
In extracts obtained by treating rye embryo ribosomes with 0.5 M NH4Cl, nuclease activity was noted towards double-stranded RNA from virus of Penicillium chrysogenum and towards synthetic poly (A)-poly (U) and poly (I)-poly (C) complexes. 相似文献
7.
Paul Nieuwenhuysen Julius Clauwaert 《Journal of biochemical and biophysical methods》1981,5(5):279-286
It is impossible to measure the diffusion coefficient of macromolecules directly and accurately by quasi—elastic light scattering, when aggregates cannot be eliminated from the solutions to be investigated. Nevertheless, a simple method can be applied to overcome this problem in many cases. Aggregates are separated from the monomeric macromolecules by rate-zonal sedimentation in a CsCl density gradient in a transparent centrifugation tube; the monomers are then located by laser light scattering intensity measurements; photon correlation spectroscopy of the scattered light finally yields their diffusion coefficient. The viscosity of aqueous CsCl solutions at different temperatures and concentrations allows a good separation by centrifugation and a low uncertainty in the reduction of the measured diffusion coefficient to standard conditions.The application of the method to eukaryotic large ribosomal subunits is described as an example. 相似文献
8.
RNase activity from Chlorella was partially purified. Two RNase activities were demonstrated, one soluble and the other ribosomal. The effects on ribonuclease activity of variations in pH and temperature, and of Mg2+, Na+, and mononucleotides were examined. The RNase activities (phosphodiesterases EC 3.1.4.23) were both endonucleolytic, releasing oligonucleotides, and cyclic nucleotide intermediates, but exhibited different specificities in releasing mononucleotides from RNA. The ribosomal activity released 3′-GMP, and after prolonged incubation 3′-UMP, but the soluble activity released 3′-GMP, 3′-AMP and 3′-UMP. Neither ofthe RNase preparations hydrolysed DNA, nor released 5′-nucleotides from RNA. Increased ribosomal RNase activity was related to dissociation of ribosomes, and latency of ribosomal RNase activity was demonstrated. The possible in vivo distribution of RNases is discussed. 相似文献
9.
The importance of the absolute and relative concentrations of monovalent and divalent cations and centrifugal speed (pressure) in the dissociation of mung bean 80S ribosomes has been examined. In the absence of Mg2+ ions, ribosome monomers yield 47S and 34S particles. Fixation with glutaraldehyde, however, indicates that this dissociation pattern is largely dependent upon high pressures developed during centrifugation and that in the absence of such artifacts the immediate product of Mg-free conditions is a 74S particle. Since 74S particles rapidly revert to the 80S form when Mg is replaced, this would appear to be a conformational change. Ribosomes were also dissociated in the presence of Mg2+ ions if the K+ ion concentration was raised. Three major particles were produced, 38S and 49S from the small ribosomal sub-unit and 60S from the large sub-unit. A proportion of the 80S monomer population is more resistant to dissociation. Experiments with puromycin indicate that the more resistant fraction probably represents ribosomes completed with nascent polypeptide resulting from polysome breakdown. 相似文献
10.