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1.
When S(35)-labeled soluble RNA from Escherichia coli K 38 is subjected to gel filtration, four fractions of RNA are obtained by elution. Only one RNA fraction, the transfer RNA, contains sulfur, presumably as thionucleotides. Treatment with ribonuclease suggests that the incorporated sulfur is an integral part of the polynucleotide chain; digestion with alkali yields a mixture of products containing sulfur, the major one being eluted in a position similar to uridine diphosphate upon Dowex-l chromatography. Analysis by countercurrent distribution of S(35)-labeledtransfer RNA from E. coli B reveals that the incorporated sulfur is found in many RNA's that accept amino acids, but the possibility remains that not all acceptor RNA's contain sulfur. 相似文献
2.
Ribosomal RNA synthesis and processing in a particulate site in the HeLa cell nucleus 总被引：43，自引：0，他引：43
A particulate fraction has been isolated from detergent-prepared HeLa cell nuclei. The fraction consists largely of organelles that resemble the nucleoli of intact cells. The 45S RNA that is precursor to 28S and 18S ribosomal RNA is associated with the fraction. The 32S RNA that is labeled after the 45S RNA and is the apparent precursor to 28S RNA is also associated with the fraction. The nucleoplasm contains 28S RNA that behaves as an intermediate between the 32S nucleolar RNA and the 28S cytoplasmic RNA. 相似文献
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Reconstitution of 30S ribosomal particles from 16S ribosomal RNA and total proteins, or from core proteins and split proteins obtained from the ribosomes of strains of Escherichia coli sensitive to and resistant to spectinomycin, shows that the split protein fraction determines the response of polypeptide synthesis in virto to spectinomycin. Reconstitution of active particles in the presence of isolated split proteins allowed the identification of the single split protein responsible for spectinomycin sensitivity. 相似文献
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A catalytic RNA and its gene from Salmonella typhimurium 总被引：16，自引：0，他引：16
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Specific interactions in RNA enzyme-substrate complexes 总被引：27，自引：0，他引：27
Analysis of crosslinked complexes of M1 RNA, the catalytic RNA subunit of ribonuclease P from Escherichia coli, and transfer RNA precursor substrates has led to the identification of regions in the enzyme and in the substrate that are in close physical proximity to each other. The nucleotide in M1 RNA, residue C92, which participates in a crosslink with the substrate was deleted and the resulting mutant M1 RNA was shown to cleave substrates lacking the 3' terminal CCAUCA sequence at sites several nucleotides away from the normal site of cleavage. The presence or absence of the 3' terminal CCAUCA sequence in transfer RNA precursor substrates markedly affects the way in which these substrates interact with the catalytic RNA in the enzyme-substrate complex. The contacts between wild-type M1 RNA and its substrate are in a region that resembles part of the transfer RNA "E" (exit) site in 23S ribosomal RNA. These data demonstrate that in RNA's with very different cellular functions, there are domains with similar structural and functional properties and that there is a nucleotide in M1 RNA that affects the site of cleavage by the enzyme. 相似文献
8.
Two new sulfur-containing pyrimidine nucleotides have been isolated from hydrolyzates of Escherichia coli transfer RNA. The structures, 2-thiocytosine and 5-methylaminomethyl-2-thiouracil, have been assigned to the bases as a result of study of ultraviolet and mass spectra. An acid-degradation product, S-methylamino-methyluracil, has been synthesized and is identical to that derived from the natural product. 相似文献
9.
Catalytic activity of an RNA molecule prepared by transcription in vitro 总被引：26，自引：0，他引：26
10.
LANGRIDGE R 《Science (New York, N.Y.)》1963,140(3570):1000
A reflection between 45 and 50 A has been observed in x-ray diffraction patterns from ribosomes extracted from Escherichia coli, Drosophila larvae, rat liver, and rabbit reticulocytes. This spacing appears to correspond to a common substructural feature within the ribosomes. The intensity distribution is consistent with a model in which part of the RNA is in the form of four or five parallel double helices 45 to 50 A apart. 相似文献
11.
Coupling of Tetrahymena ribosomal RNA splicing to beta-galactosidase expression in Escherichia coli 总被引：10，自引：0，他引：10
Splicing of the Tetrahymena ribosomal RNA precursor is mediated by the folded structure of the RNA molecule and therefore occurs in the absence of any protein in vitro. The Tetrahymena intervening sequence (IVS) has been inserted into the gene for the alpha-donor fragment of beta-galactosidase in a recombinant plasmid. Production of functional beta-galactosidase is dependent on RNA splicing in vivo in Escherichia coli. Thus RNA self-splicing can occur at a rate sufficient to support gene expression in a prokaryote, despite the likely presence of ribosomes on the nascent RNA. The beta-galactosidase messenger RNA splicing system provides a useful method for screening for splicing-defective mutations, several of which have been characterized. 相似文献
12.
胆木叶抗MRS活性研究 总被引：3，自引：0，他引：3
以耐甲氧西林金黄色葡萄球菌（MRS）、大肠杆菌、普通金黄色葡萄球菌、普通变形杆菌、枯草芽孢杆菌为供试菌种,采用滤纸片琼脂扩散法研究胆木叶提取物的体外抑菌活性。结果表明,以40％以上体积分数乙醇为提取剂时,胆木叶提取物对MRS具有抑静活性,且乙醇的体积分数越大,提取物的抑菌活性越强;胆木叶乙醇提取物中的中高极性溶剂萃取段抑菌活性最强。胆木叶水煮液对大肠杆菌具有抑菌活性,醇提液对大肠杆菌只有极弱的抑菌活性。胆木叶醇提液和水煮液对普通金黄色葡萄球菌、普通变形杆菌、枯草芽孢杆菌只有极弱的抑菌活性。 相似文献
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Autocatalytic synthesis of a viral RNA in vitro 总被引：15，自引：0，他引：15
Experiments with an RNA-dependent RNA polymerase ("replicase") purified from Escherichia coli infected with an RNA bacteriophage (Qbeta) demonstrate that the enzyme generates a polynucleotide of the same molecular weight as viral RNA; the "replicase" cannot distinguish the polynucleotide from its own RNA genome. By starting reactions at input ratios below the saturation levels of template to enzyme, autocatalytic kinetics of RNA increase are observed. The data are consistent with the conclusion that self-propagation of complete viral genomes is occurring in this simple system. 相似文献
14.
为了剖析桃果实中脱落酸受体ABAR/CHLH蛋白的结合活性,从桃果实中提取总RNA,采用RT-PCR方法,以桃果实RNA逆转录的cDNA为模板,扩增出ABAR/CHLH基因的结合区功能片段C369,回收目的片段并测序,基因片段长度为1 121 bp,编码369个氨基酸残基,分子量约为40 kD。利用BamHⅠ和NotI酶切位点将该片段编码区插入原核表达载体pET-28a（＋）中,构建ABAR/CHLH基因片段原核表达载体pET28a-C369,经菌落PCR和测序确证后,转化E.coliRosetta（DE3）,通过IPTG诱导其表达His-CHLH融合蛋白。通过SDS-PAGE检测及Ni-NTA琼脂糖树脂亲和层析柱纯化目的蛋白,并用纯化复性的His-CHLH C369融合蛋白制备抗体。 相似文献
15.
Heme requirement for reproduction of a free-living nematode 总被引：1，自引：0，他引：1
The free-living hermaphroditic nematode Caernorhabditis briggsae has a nutritional requirement for heme. The organism can be subcultured repeatedly in a chemically defined axenic medium that contains autoclaved bacterial cells (Escherichia coli) and sterols if a hemeprotein-containing fraction from liver is present. Pure myoglobin, hemoglobin, cytochrome c, and hemin, respectively, can substitute effectively for the liver fraction. 相似文献
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Using the atomic structures of the large ribosomal subunit from Haloarcula marismortui and its complexes with two substrate analogs, we establish that the ribosome is a ribozyme and address the catalytic properties of its all-RNA active site. Both substrate analogs are contacted exclusively by conserved ribosomal RNA (rRNA) residues from domain V of 23S rRNA; there are no protein side-chain atoms closer than about 18 angstroms to the peptide bond being synthesized. The mechanism of peptide bond synthesis appears to resemble the reverse of the acylation step in serine proteases, with the base of A2486 (A2451 in Escherichia coli) playing the same general base role as histidine-57 in chymotrypsin. The unusual pK(a) (where K(a) is the acid dissociation constant) required for A2486 to perform this function may derive in part from its hydrogen bonding to G2482 (G2447 in E. coli), which also interacts with a buried phosphate that could stabilize unusual tautomers of these two bases. The polypeptide exit tunnel is largely formed by RNA but has significant contributions from proteins L4, L22, and L39e, and its exit is encircled by proteins L19, L22, L23, L24, L29, and L31e. 相似文献
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Cytokinin activity: localization in transfer RNA preparations 总被引：15，自引：0，他引：15
F Skoog D J Armstrong J D Cherayil A E Hampel R M Bock 《Science (New York, N.Y.)》1966,154(754):1354-1356
Transfer RNA from yeast, liver, and Escherichia coli has cytokinin activity in the tobacco callus bioassay, whereas ribosomal RNA from yeast is inactive. In contrast to fractions of yeast transfer RNA rich in serine acceptor and cytokinin activity, preparations (70 to 90 percent pure) of arginine transfer RNA(2), glycine transfer RNA, phenylalanine transfer RNA, and valine transfer RNA(1) and of highly purified alanine transfer RNA from yeast were inactive at concentrations of 20 to 2500 micrograms per liter. One molecule of 6-(gamma,gamma-dimethylallylamino) purine per 20 molecules of yeast tRNA would account for the observed cytokinin activity. The number of major molecular species contributing to cytokinin activity of transfer RNA, therefore, must be small. 相似文献
18.
A persistent untranslated sequence within bacteriophage T4 DNA topoisomerase gene 60 总被引：30，自引：0，他引：30
W M Huang S Z Ao S Casjens R Orlandi R Zeikus R Weiss D Winge M Fang 《Science (New York, N.Y.)》1988,239(4843):1005-1012
A 50-nucleotide untranslated region is shown to be present within the coding sequence of Escherichia coli bacteriophage T4 gene 60, which encodes one of the subunits for its type II DNA topoisomerase. This interruption is part of the transcribed messenger RNA and appears not to be removed before translation. Thus, the usual colinearity between messenger RNA and the encoded protein sequence apparently does not exist in this case. The interruption is bracketed by a direct repeat of five base pairs. A mechanism is proposed in which folding of the untranslated region brings together codons separated by the interruption so that the elongating ribosome may skip the 50 nucleotides during translation. The alternative possibility, that the protein is efficiently translated from a very minor and undetectable form of processed messenger RNA, seems unlikely, but has not been completely ruled out. 相似文献
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X-ray diffraction patterns of transfer RNA consistent with the presence of short parallel helices in the molecule 总被引：1，自引：0，他引：1
X-ray diffraction data of yeast formylmethionine transfer RNA, Escherichia coli phenylalanine transfer RNA, and Escherichia coli arginine transfer RNA single crystals are compared with the Fourier transform of a helix. The results are consistent with the presence of short parallel double helical segments in the transfer RNA molecules. 相似文献
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大肠杆菌引发的仔猪腹泻是养猪生产中存在的普遍疾病,是影响养猪业经济效益 的重要因素。本实验以发病和未发病的仔猪脾脏为对照,进行差异显示研究,筛选仔猪腹泻抗 性相关特异表达基因。在脾脏未发病池中检测到一条与Nck转导蛋白同源的特异表达EST、序 列;作为信号转导蛋白,Nck通过活化免疫细胞,在免疫系统中发挥作用。同时,Nck也是大肠 杆菌附着在小肠上皮细胞,并释放毒素这一过程中的一个关键因子。大肠杆菌粘附在小肠上产 生的信号可能是通过Nck传至中枢免疫器官,引发T细胞的大量细胞增殖、转换、分化和程序 性死亡,从而为积极防御外界抗原做准备。 相似文献