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排序方式: 共有302条查询结果,搜索用时 15 毫秒
81.
Juan Carlos Salazar Roberto Zúiga Gregory Raczniak Hubert Becker Dieter Sll Omar Orellana 《FEBS letters》2001,500(3)
The gatC, gatA and gatB genes encoding the three subunits of glutamyl-tRNAGln amidotransferase from Acidithiobacillus ferrooxidans, an acidophilic bacterium used in bioleaching of minerals, have been cloned and expressed in Escherichia coli. As in Bacillus subtilis the three gat genes are organized in an operon-like structure in A. ferrooxidans. The heterologously overexpressed enzyme converts Glu-tRNAGln to Gln-tRNAGln and Asp-tRNAAsn to Asn-tRNAAsn. Biochemical analysis revealed that neither glutaminyl-tRNA synthetase nor asparaginyl-tRNA synthetase is present in A. ferrooxidans, but that glutamyl-tRNA synthetase and aspartyl-tRNA synthetase enzymes are present in the organism. These data suggest that the transamidation pathway is responsible for the formation of Gln-tRNA and Asn-tRNA in A. ferrooxidans. 相似文献
82.
The catalytic site of the pectin biosynthetic enzyme alpha-1,4-galacturonosyltransferase is located in the lumen of the Golgi 下载免费PDF全文
Alpha-1,4-galacturonosyltransferase (GalAT) is an enzyme required for the biosynthesis of the plant cell wall pectic polysaccharide homogalacturonan (HGA). GalAT activity in homogenates from pea (Pisum sativum L. var. Alaska) stem internodes co-localized in linear and discontinuous sucrose gradients with latent UDPase activity, an enzyme marker specific for Golgi membranes. GalAT activity was separated from antimycin A-insensitive NADH:cytochrome c reductase and cytochrome c oxidase activities, enzyme markers for the endoplasmic reticulum and the mitochondria, respectively. GalAT and latent UDPase activities were separated from the majority (80%) of callose synthase activity, a marker for the plasma membrane, suggesting that little or no GalAT is present in the plasma membrane. GalAT activities in proteinase K-treated and untreated Golgi vesicles were similar, whereas no GalAT activity was detected after treating Golgi vesicles with proteinase K in the presence of Triton X-100. These results demonstrate that the catalytic site of GalAT resides within the lumen of the Golgi. The products generated by Golgi-localized GalAT were converted by endopolygalacturonase treatment to mono- and di-galacturonic acid, thereby showing that GalAT synthesizes 1-->4-linked alpha-D-galacturonan. Our data provide the first enzymatic evidence that a glycosyltransferase involved in HGA synthesis is present in the Golgi apparatus. Together with prior results of in vivo labeling and immunocytochemical studies, these results show that pectin biosynthesis occurs in the Golgi. A model for the biosynthesis of the pectic polysaccharide HGA is proposed. 相似文献
83.
Formate hydrogenlyase and formate secretion ameliorate H2 inhibition in the hyperthermophilic archaeon Thermococcus paralvinellae 下载免费PDF全文
Begüm D. Topçuoğlu Cem Meydan Roberto Orellana James F. Holden 《Environmental microbiology》2018,20(3):949-957
Some hyperthermophilic heterotrophs in the genus Thermococcus produce H2 in the absence of S° and have up to seven hydrogenases, but their combined physiological roles are unclear. Here, we show which hydrogenases in Thermococcus paralvinellae are affected by added H2 during growth without S°. Growth rates and steady‐state cell concentrations decreased while formate production rates increased when T. paralvinallae was grown in a chemostat with 65 µM of added H2(aq). Differential gene expression analysis using RNA‐Seq showed consistent expression of six hydrogenase operons with and without added H2. In contrast, expression of the formate hydrogenlyase 1 (fhl1) operon increased with added H2. Flux balance analysis showed H2 oxidation and formate production using FHL became an alternate route for electron disposal during H2 inhibition with a concomitant increase in growth rate relative to cells without FHL. T. paralvinellae also grew on formate with an increase in H2 production rate relative to growth on maltose or tryptone. Growth on formate increased fhl1 expression but decreased expression of all other hydrogenases. Therefore, Thermococcus that possess fhl1 have a competitive advantage over other Thermococcus species in hot subsurface environments where organic substrates are present, S° is absent and slow H2 efflux causes growth inhibition. 相似文献
84.
85.
A flow cytometer coupled to a scanning monochromator and a fluorescence microscope were used to characterize the fluorescence spectrum of Pseudo‐nitzschia multiseries (Hasle) Hasle, a pennate diatom that produces the neurotoxin domoic acid, a lethal amnesic. In this research, we characterize the fluorescence spectrum of P. multiseries in vivo over the wavelength range of 360 to 850 nm and show that this diatom autofluoresces blue when excited with UV light (350–365 nm). The autofluorescence characterization of Pseudo‐nitzschia may provide new methods for rapid in situ monitoring of diatom populations and reiterates the usefulness of flow cytometry in the analysis and study of marine phytoplankton. 相似文献
86.
Orellana M Rodrigo R Thielemann L Guajardo V 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2000,126(2):105-111
In the liver, seven days of bile duct ligation (BDL) decreases the cytochrome P-450 content and the UDP-glucuronyl transferase activity. Also, a decrease in the water soluble antioxidant mechanism reflected in the activities of the enzymes superoxide dismutase (SOD), catalase and the glutathione peroxidase (GTPx) was found in the liver but not in the kidney. Despite an increase in the amount of the GSH in the liver, increased lipid peroxidation is produced in the BDL rats, as indicated by the levels of malondialdehyde (MDA). The kidney responded in a different way to cholestasis, decreasing only the UDP-glucuronyl transferase activity and increasing the levels of GSH and MDA. In the red blood cells the activity of the antioxidant enzymes SOD, GTPx and catalase and the content of GSH were not modulated by cholestasis. In conclusion, disturbance of the oxidant-antioxidant balance might be responsible for cholestatic liver injury and impaired renal function in BDL rats. 相似文献
87.
88.
Marcela Aldana José M. Pulgar Nathalie Orellana F. Patricio Ojeda M. Roberto García-Huidobro 《EcoHealth》2014,11(2):215-226
The rapid increase in body size and abundance of most species inside Management and Exploitations Areas for Benthic Resources (MEABRs) has led to the proposal of these areas as a good complement for achieving the conservation objectives of Marine Protected Areas (MPAs). However, when evaluating MEABRs and MPAs as conservation and/or management tools, their impact upon parasite populations has rarely been considered, despite the fact that epidemiological theory suggests an increased susceptibility to parasitism under high population abundance. We evaluated the effects of MEABRs on the parasite abundance of Proctoeces lintoni and its impact on the growth of the host limpet Fissurella crassa in central Chile. Parasitic magnitude was higher inside MEABRs than in Open-Access Areas, and parasitized limpets showed a greater shell length, muscular foot biomass, and gonadosomatic index compared to non-parasitized limpets of the same age. Our results suggest that the life cycle of P. lintoni and, consequently, its trophic links have been strengthened inside MEABRs. The increased growth rate could reduce the time required to reach the minimum catch size and increase the reproductive and muscular output of the host population. Thus, parasitism should be considered in the conservation and management of economically important mollusk hosts. 相似文献
89.
Mayo S Monfort S Roselló M Orellana C Oltra S Armstrong J Català V Martínez F 《Cytogenetic and genome research》2011,135(2):93-101
Loss-of-function mutations of the MECP2 gene are the cause of most cases of Rett syndrome in females, a progressive neurodevelopmental disorder characterized by severe mental retardation, global regression, hand stereotypies, and microcephaly. On the other hand, gain of dosage of this gene causes the MECP2 duplication syndrome in males characterized by severe mental retardation, absence of speech development, infantile hypotonia, progressive spasticity, recurrent infections, and facial dysmorphism. Female carriers of a heterozygous duplication show a skewed X-inactivation pattern which is the most probable cause of the lack of clinical symptoms. In this paper, we describe a girl with a complex de novo copy number gain at Xq28 and non-skewed X-inactivation pattern that causes mental retardation and motor and language delay. This rearrangement implies triplication of the MECP2 and IRAK1 genes, but it does not span other proximal genes located in the common minimal region of patients affected by the MECP2 duplication syndrome. We conclude that the triplication leads to a severe phenotype due to random X-inactivation, while the preferential X chromosome inactivation in healthy carriers may be caused by a negative selection effect of the duplication on some proximal genes like ARD1A or HCFC1. 相似文献
90.
Schijman AG Bisio M Orellana L Sued M Duffy T Mejia Jaramillo AM Cura C Auter F Veron V Qvarnstrom Y Deborggraeve S Hijar G Zulantay I Lucero RH Velazquez E Tellez T Sanchez Leon Z Galvão L Nolder D Monje Rumi M Levi JE Ramirez JD Zorrilla P Flores M Jercic MI Crisante G Añez N De Castro AM Gonzalez CI Acosta Viana K Yachelini P Torrico F Robello C Diosque P Triana Chavez O Aznar C Russomando G Büscher P Assal A Guhl F Sosa Estani S DaSilva A Britto C Luquetti A Ladzins J 《PLoS neglected tropical diseases》2011,5(1):e931