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991.
Insulin treatment of HeLa S3 cells activates an S6-phosphorylating protein kinase. Although this enzyme has chromatographic properties resembling those of described proteolytic fragments of other protein kinases, namely protein kinase C, protease-activated kinase II and histone-4 protein kinase, and although insulin has been proposed by others to cause S6 phosphorylation via proteolytic protein kinase activation, the insulin-induced increase in S6-kinase activity described here is probably not due to proteolysis. Rather, the activity indicates the existence, in HeLa cells, of an interconvertible S6 kinase, since the insulin-induced activity increase was rapidly reversed under hyperthermic stress, and since this effect of hyperthermia was itself reversible. The S6-kinase activities from serum- and from insulin-stimulated HeLa cells resemble each other closely and are likely to represent the same enzyme. The enzyme may therefore mediate both signals delivered by mitogens and the insulin signal. Analysed at an in vitro transfer of 1 mol phosphate/mol S6, this S6 kinase activity does not phosphorylate the (principal) S6 site recognized by the cAMP-dependent protein kinase. 相似文献
992.
A Sóoki-Tóth G Bánfalvi J Sz?ll?si E Kirsten M Staub F Antoni E Kun 《Experimental cell research》1989,184(1):44-52
Thymic cells were isolated at intervals of between 0 and 144 h from mice that received one intraperitoneal injection of emetine (33 mg/kg), and thymus weight, incorporation of [14C]leucine into proteins and [3H]thymidine into DNA in intact thymic cells, as well as initial rates of protein ADP-ribosylation in permeabilized cells [A. Sóoki-Tóth, F. Asghari, E. Kirsten, and E. Kun (1987) Exp. Cell Res. 170, 93] were simultaneously monitored. The effect of emetine as an inhibitor of protein synthesis [F. Antoni, N. G. Luat, I. Csuka, I. Oláh, A. Sóoki-Tóth, and G. Bánfalvi (1987) Int. J. Immunopharmacol. 9, 333] corresponds to the induction of sequential cellular events, such as cell exit and remigration, by other antimitotic agents [C. Penit and F. Vasseur (1988) J. Immunol. 140, 3315] and produces an activation of proliferation of cells reentering into this organ. Proliferation, as demonstrated by a large increase in DNA synthesis and entrance into S phase, was kinetically related to an apparent increase in poly(ADP-ribose) polymerase activity in thymic cells and a highly significant in vitro ADP-ribosylation of histone H3. Since no DNA fragmentation occurred in thymic cells, as tested by a fluorometric technique [C. Birnboim and J. J. Jevac (1981) Cancer Res. 41, 1889], it is probable that a selective activation of poly(ADP-ribose) polymerase may have been induced in cells that undergo differentiation and proliferation while repopulating the thymus. 相似文献
993.
Interactions of human lymphoblasts with targeted vesicles containing Sendai virus envelope proteins 总被引:2,自引:0,他引:2
We have studied the internalization of targeted fusogenic liposome content to leukemic T cells (CEM) in vitro. We describe a method for the covalent coupling of T101 antibody to the surface of liposomes and the incorporation of fusogenic viral protein into the liposome membrane. Hygromycin B, an impermeant inhibitor of protein synthesis, was encapsulated in the targeted fusogenic liposomes and delivered directly to the cytoplasm of leukemic T cells by fusion between the two membranes. The cytotoxic effect was measured by [3H]thymidine incorporation. We show that CEM are rapidly and specifically killed by the drug encapsulated in the targeted fusogenic liposomes. This effect is due to the binding of the liposome by means of the antibody and then to the fusion of the liposome with the targeted cell membrane, mediated by F protein. 相似文献
994.
The primary structure of rat ribosomal protein L18a 总被引:3,自引:0,他引:3
The amino acid sequence of rat ribosomal protein L18a was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein L18a contains 175 amino acids and has a molecular mass of 20,047 Da. Hybridization of the cDNA to digests of rat nuclear DNA and to a preparation of poly(A)+ mRNA suggests that there are 8-11 copies of the L18a gene and that the mRNA for the protein is about 700 nucleotides in length. Rat L18a is related to Schizosaccharomyces pombe L17 and perhaps to Halobacterium marismortui L19. 相似文献
995.
Human testis cDNA for the regulatory subunit RII alpha of cAMP-dependent protein kinase encodes an alternate amino-terminal region 总被引:3,自引:0,他引:3
Phosphorylations catalyzed by cAMP-dependent protein kinase are essential for sperm motility, and type II cAMP-dependent protein kinase in mature sperm has been shown to be firmly bound to the flagellum via the regulatory subunit, RII. The present study documents high-levelled expression of a human, testis-specific RII alpha mRNA (2.0 kb) analogous to the rat mRNA which is induced in haploid germ cells [(1988) FEBS Lett. 229, 391-394]. We report the molecular cloning of a full-length human cDNA corresponding to this unique testis mRNA, and the presence of an alternative amino-terminal region (amino acids 45-75) of the predicted RII alpha protein (404 amino acids) compared with the previously published mouse and rat sequences. However, this alternate region is also shown to be present in RII alpha mRNA (7.0 kb) of human somatic cells. Our data indicate the divergent amino-terminal sequence to be due to species differences, suggesting an active evolutionary pressure on this particular region, which could be involved in subcellular attachment of RII alpha and thereby localization of kinase activity to certain targets within the cell. 相似文献
996.
997.
The 18p- syndrome. Report of five cases 总被引:2,自引:0,他引:2
R M Zumel M T Darnaude A Delicado A Diaz de Bustamante M L de Torres I López-Pájares 《Annales de génétique》1989,32(3):160-163
Five children, three males and two females were found to have a short arm deletion of chromosome 18. Four of them display some of the typical features of this syndrome: microcephaly, round face, hypertelorism, broad-based nose, "carp-mouth", microrethrognathia, pterygium colli, dysplastic and low set ears, clinodactily, failure to grow, muscular hypotony and mental retardation. Different hypotheses are discussed in order to explain the variable phenotypical expression of the 18 p-syndrome. 相似文献
998.
Biological degradation of 2,4-dichlorophenoxyacetic acid: chloride mass balance in stirred tank reactors. 总被引:1,自引:1,他引:0 下载免费PDF全文
A mass balance was developed for the degradation of 2,4-dichlorophenoxyacetic acid by a mixed culture. Batch culture experiments showed the degradation to be an acid-producing step. Inorganic chloride concentration consistently correlated with the expected value and with base consumption to maintain a constant pH. 相似文献
999.
Cyanase-mediated utilization of cyanate in Pseudomonas fluorescens NCIB 11764. 总被引:1,自引:1,他引:0 下载免费PDF全文
Pseudomonas fluorescens NCIB 11764 was capable of utilizing cyanate (OCN-) as a sole nitrogen source for growth. Crude cell extracts from cells grown on cyanate, but not on ammonium sulfate, were induced for an enzyme catalyzing cyanate conversion to ammonia. Enzymatic activity was shown to be bicarbonate dependent and specific for cyanate as a substrate, suggesting that cyanate utilization in this organism is facilitated by an enzyme resembling cyanase (cyanate amidohydrolase; EC 3.5.5.3), as described previously in Escherichia coli and Flavobacterium sp. 相似文献
1000.
Growth and luminescence of the bacterium Xenorhabdus luminescens from a human wound. 总被引:7,自引:2,他引:5 下载免费PDF全文
Xenorhabdus luminescens, a newly isolated luminous bacterium collected from a human wound, was characterized. The effects of ionic strength, temperature, oxygen, and iron on growth and development of the bioluminescent system were studied. The bacteria grew and emitted light best at 33 degrees C in a medium with low salt, and the medium after growth of cells to a high density was found to have antibiotic activity. The emission spectrum peaked at 482 nm in vivo and at 490 nm in vitro. Both growth and the development of luminescence in X. luminescens required oxygen and iron. The isolated luciferase itself exhibited a temperature optimum at about 40 degrees C; after purification by affinity chromatography, it showed two bands (52 and 41 kilodaltons) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicative of an alpha and beta subunit structure. Reduced flavin mononucleotide (Km of 1.4 microM) and tetradecanal (Km of 2.1 microM) were the best substrates for the luciferase, and the first-order decay constant under these conditions at 37 degrees C was 0.79 s-1. 相似文献