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1.
A new ribosomal protein of 38 kDa, named A0, was detected in yeast ribosomes on immunoblotting. The antibody used here was that against A1/A2, 13 kDa acidic ribosomal proteins which cross-reacted with A0. Although A0 and A1/A2 share common antigenic determinants, they differ in the following biochemical properties. While A1/A2 could be extracted from ribosomes with ethanol and ammonium sulfate, A0 could not. A0 gave two protein spots in a less acidic region than for A1/A2 on two-dimensional gel electrophoresis. The heterogeneity observed for A0 was ascribable to phosphorylation because one spot disappeared after treatment of the ribosomes with phosphatase. The syntheses of A0 and A1/A2 are directed by different mRNA species, as judged with a cell-free translation system, ruling out the possibility that A0 is a precursor of A1/A2. Although a mammalian ribosomal protein equivalent to A0 has been shown to be associated with 13 kDa acidic proteins in the cytoplasm, essentially no A0 was detected on immunoblotting in the yeast cytosol, while a small but detectable amount of A1/A2 was present. The possibility that A0 is a eukaryotic equivalent of L10 of Escherichia coli is discussed. 相似文献
2.
Ricin is a potent cytotoxic protein derived from the higher plant Ricinus communis that inactivates eukaryotic ribosomes. In this paper we have studied the mechanism of action of ricin A-chain on rat liver ribosomes in vitro. Our findings indicate that the toxin inactivates the ribosomes by modifying both or either of two nucleoside residues, G4323 and A4324, in 28 S rRNA. These nucleotides are located close to the alpha-sarcin cleavage site and become resistant to all ribonucleases tested. The examination of the lability of phosphodiester bonds of these nucleotides to both mild alkaline digestion and aniline treatment at acidic pH suggests that the base of A4324 is removed by the toxin. This unique activity of ricin A-chain was also observed when naked 28 S rRNA is used as a substrate, indicating that the toxin directly acts on the RNA. Similar activity on 28 S rRNA is also exhibited by abrin and modeccin, ricin-related toxins, suggesting a general mechanistic pathway for ribosome inactivation by lectin toxins. 相似文献
3.
Takuo Yamakura Akio Hagihara Sukristijono Sukardjo Husato Ogawa 《Ecological Research》1987,2(3):215-227
The form of tropical trees was studied with reference to the production structure of the component individuals of a tropical
rain forest stand in Sebulu, East Kalimantan in Indonesian Borneo, since the production structure as a physical or bio-economical
basis of tree form still remains obscure in tropical rain forests. The pipe model theory successfully explained the crown
shapes of different trees, and its parameter, designated as specific pipe length, suggested an increase in the cost of leaf
mass growth with an increase in crown size. A mathematical model consisting of exponential functions of aboveground height
was applied for describing stem form, and its properties were examined through changes in its coefficients and by adopting
an assumption of the geometrical similarity of individual stem form as a criterion for comparing differences in stem form
among individual trees. Furthermore, the cost of buttersses was discussed using the relation between bole- and buttress weight
calculated from the mathematical model. 相似文献
4.
Min-Hua Zong Toshiaku Fukui Takuo Kawamoto Atsuo Tanaka 《Applied microbiology and biotechnology》1991,36(1):40-43
Summary Bioconversion of three organosilicon compounds of different chain length between the silicon atom and the hydroxyl group (Me3Si(CH2)nOH, n = 1–3) by horse liver alcohol dehydrogenase (HLADH, EC 1.1.1.1.) was studied. Furthermore, the effect of the silicon atom on the HLADH-catalysed reaction was examined in comparison with the corresponding carbon compounds. HLADH could catalyse the dehydrogenation of trimethylsilyeethanol (n = 2) and trimethylsilylpropanol (n = 3). Trimethylsilylethanol was a better substrate than both its carbon analogue, 3,3-dimethylbutanol, and ethanol. The improved activity of HLADH on trimethylsilylethanol could be accounted for by a higher affinity toward HLADH and a lower activation energy of the reaction by HLADH than those of the carbon counterpart. These are derived from physical properties of the silicon atom, that is, the lower electronegativity and the bigger radius than those of the carbon atom. In contrast, HLADH showed no activity on trimethylsilylmethanol (n = 1), whereas it catalysed the dehydrogenation of the carbon analogue, 2,2-dimethylpropanol, fairly well. The reason for the inactivity of HLADH in the case of trimethylsilylmethanol based on the electric effect of the silicon atom is also discussed.
Offsprint requests to: A. Tanaka 相似文献
5.
The site of action of the A-chain of mistletoe lectin I on eukaryotic ribosomes. The RNA N-glycosidase activity of the protein 总被引:4,自引:0,他引:4
The site of action of the A-chain of mistletoe lectin (ML-A) from Viscum album on eukaryotic ribosomes was studied. Treatment of rat liver ribosomes with ML-A, followed by treatment of the isolated rRNA with aniline, caused the release of a fragment with about 450 nucleotides from 28 S rRNA. Further analysis of nucleotide sequences of this fragment revealed that the aniline-sensitive site of phosphodiester bond was between positions A-4324 and G-4325 in 28 S rRNA. These results indicate that ML-A inactivates the ribosomes by cleaving a N-glycosidic bond at A-4324 of 28 S rRNA in the ribosomes as ricin A-chain does. 相似文献
6.
Y Endo Y L Chan A Lin K Tsurugi I G Wool 《The Journal of biological chemistry》1988,263(17):7917-7920
An oligoribonucleotide (35-mer) that mimics the alpha-sarcin and the ricin region of eukaryotic 28 S rRNA was transcribed in vitro from a synthetic template with T7 RNA polymerase and was used to test whether the specificity of the hydrolysis by the toxins was retained. alpha-Sarcin, at a low concentration, cleaved a single phosphodiester bond on the 3' side of a guanosine residue in the synthetic oligomer that corresponds to G-4325 in 28 S rRNA, the site of action of the toxin in intact ribosomes. At a high concentration of alpha-sarcin, the substrate (35-mer) was hydrolyzed after each of its purines. alpha-Sarcin was without an effect on a synthetic RNA (20-mer) that reproduces the near universal sequence of nucleotides in the loop, but lacks the stem, of the toxin's domain. Thus, the specificity of the attack of alpha-sarcin on a precise region of 28 S rRNA appears to be contingent on the sequence of the nucleotides and the structure of the domain. Ricin depurinated a nucleotide in the synthetic oligomer (35-mer), and in the presence of aniline the phosphoribose backbone was cleaved at a position that conforms to A-4324 in 28 S rRNA, the site of action of the toxin in vivo. 相似文献
7.
利用脂肪酶在有机溶剂中催化对映选择性酯化反应对外消旋薄荷醇进行了有效的光学拆分。对分别使用酸酐和相应的游离羧酸作酰基给体时的反应性能进行了比较。发现酸酐的反应性远高于对应的游离羧酸,但在酶的催化作用下酸酐易水解成为游离羧酸;在微水系统中使用过高浓度的酸酐会导致酶缺水而失活,同时会促进手性醇的非选择性酯化,从而降低产物的光学纯度。然而,在连续流加丙酸酐的半批式反应系统中,所有这些缺点均可有效地克服。与使用游离丙酸的批式反应系统相比,dl-薄荷醇的反应时间缩短了一半,酶的稳定性大幅度提高,而产物l薄荷醇酯的光学纯度不相上下(>98%e)。 相似文献
8.
Albert T. Ichiki I. Reid Collmann Takuo Sonoda John A. MacGuire Kathy L. Wenzel Stephen Krauss 《Cancer immunology, immunotherapy : CII》1977,3(2):119-124
Summary The peripheral blood leukocytes from 29 patients with adenocarcinoma of the colon were studied sequentially for the T-cell level, the rosette-inhibition titer of antithymocyte globulin and the blastogenic response to PHA and Con A to evaluate the T-cell immunocompetence. The level of E-rosette-forming cells and the blastogenic response did not reflect the immunocompetence of the T-cell population. Fluctuations in the rosette-inhibition titer of antithymocyte globulin (ATG) were observed; an increased ATG titer indicated an unfavorable clinical course, while a decreased ATG titer was observed with patients who had a favorable clinical course. The rosette-inhibition titer with antithymocyte globulin was observed to be an important indicator of competent T cells in patients with colorectal cancer.Supported by the Physicians' Medical Education and Research Foundation and General Research Supports FundsAbbreviations used that are not spelled out in the text are: AET 2-aminoethylisothiouronium bromide; ATG Antithymocyte globulin; ALG Antilymphocyte globulin; E-RFC Erythrocyte rosette-forming cells; PHA Phytohemagglutinin; Con A Concanavalin A; E Sheep erythrocyte 相似文献
9.
A new method for the production of pectin from citrus peel was developed. For this purpose, a microorganism which produces a protopectin-solubilizing enzyme was isolated and identified as a variety of Trichosporon penicillatum. The most suitable conditions for the pectin production were determined as follows. Citrus (Citrus unshiu) peel was suspended in water (1:2, wt/vol), the organism was added, and fermentation proceeded over 15 to 20 h at 30°C. During the fermentation, the pectin in the peel was extracted almost completely without macerating the peel. By this method, 20 to 25 g of pectin was obtained per kg of peel. The pectin obtained was special in that it contained neutral sugar at high levels, which was determined to have a molecular weight suitable for practical applications. 相似文献
10.
1. Nuclei of regenerating rat liver washed with Triton X-100 were found to contain a new protease. Since the enzymatic activity for degrading ribosomal proteins was inhibited in vivo by administration of E-64, a thiol protease inhibitor, the enzyme may participate in the degradation of newly synthesized ribosomal proteins and histones in regenerating rat liver nuclei as reported previously by us [Biochem. Biophys. Res. Commun. 75, 525-531 (1077)]. The optimum pH was 5.5. 2. The enzyme was extracted from washed nuclei and partially purified by gel filtration through Sepharose 6B. Its molecular weight was about 40 000. A maximal activity of partially purified enzyme was observed in the presence of 1 mM EDTA and 2 mM dithiothreitol at pH 5.5 It was inhibited by thio reagents, E-64, leupeptin and hevy metal ions. The enzyme degraded ribosomal proteins endoproteolytically and degraded most proteins tested as substrates, although liver cell sap proteins and serum albumin were less degraded than ribosomal proteins and histones, alpha-N-Benzoylarginine-beta-naphthylamide and benzoylarginine amide were not hydrolyzed. 相似文献