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排序方式: 共有419条查询结果,搜索用时 765 毫秒
411.
Sophie Lévy-Schil Laurent Debussche Sylvie Rigault Fabienne Soubrier Fabrice Bacchetta Delphine Lagneaux Josiane Schleuniger Francis Blanche Joël Crouzet Jean-François Mayaux 《Applied microbiology and biotechnology》1993,38(6):755-762
The effect of the overexpression of the bioABFCD operon on the biotin biosynthetic pathway was investigated in an Escherichia coli K12 bioR mutant with a chromosomal deletion for the biotin operon. When transformed with a multicopy number plasmid containing bioABFCD, this strain synthetized 10,000 times more biotin than a wild-type E. coli strain. In order to further increase biotin production, the bioA and bioB operons were subcloned into plasmids with stronger promoters and in some cases optimal ribosome binding sites. The new constructions led to the accumulation of large amounts of soluble Bio proteins (although not BioC) but did not improve biotin production. In all the constructed strains, BioA, BioD, and BioB activities were greatly amplified but these activitie did not correlate with the level of protein syntthesis. These strains accumulated only low levels of vitamers, auggesting that the major limiting step for higher biotin production occurs upstream from the first intermediate of the Bio pathway we assayed (7,keto-8-aminopelargonic acid). As BioC overproduction was shown to impair cell growth, we could not determine if this early step of pathway was limiting.
Correspondence to: S. Lévy-Schil 相似文献
412.
Stéphanie Godet Josiane Hérault Gaëlle Pencreac’h Françoise Ergan Céline Loiseau 《Journal of applied phycology》2012,24(6):1547-1553
Microalgae constitute a novel study area for characterising new lipolytic enzymes of biotechnological interest. A new gene from the microalga Isochrysis galbana has been isolated and a preliminary characterisation performed. The full-length cDNA contains 2,060 base pairs with an open reading frame of 1,374 nucleotides encoding a polypeptide of 457 amino acids with a predicted molecular mass of 49 kDa, and a theoretical pI of 5.65. The deduced protein includes highly conserved motifs found in α/β fold hydrolases, and shares some similarities with putative or known lipases. Sequence comparison indicated that the catalytic triad corresponds to residues Ser188, Asp306 and His391, with the nucleophilic residue Ser188 positioned within the consensus G-X-S188-X-G pentapeptide. Phylogenetic analyses established close relationships with fungal lipases and microalgal sequences. 相似文献
413.
Ivana Prokic Belinda S. Cowling Candice Kutchukian Christine Kretz Hichem Tasfaout Vincent Gache Josiane Hergueux Olivia Wendling Arnaud Ferry Anne Toussaint Christos Gavriilidis Vasugi Nattarayan Catherine Koch Jeanne Lain Roy Combe Laurent Tiret Vincent Jacquemond Fanny Pilot-Storck Jocelyn Laporte 《Disease models & mechanisms》2020,13(11)
414.
Résumé Un entomopoxvirus isolé de l'OrthoptèreAnacridium aegyptium L. est décrit. La réplication virale s'effectue dans le cytoplasme des cellules adipeuses. La microscopie électronique met
en évidence les différentes séquences de la morphogénèse virale et l'inclusion des virions à l'intérieur des corps protéiques
ovo?des. La microscopie électronique à balayage permet de visualizer quelques rares corps cristallins cubiques qui pourraient
être les homologues des fuseaux accompagnant les entomopoxvirus décrits notamment chez certains coléoptères ou lépidoptères.
相似文献
415.
Henri Faure Alain Favier Michele Tripier Josiane Arnaud 《Biological trace element research》1990,24(1):25-37
In this paper we report a method for measuring ultrafiltrable zinc in human serum by electrothermal atomic absorption spectrophtometry.
We show also that ultrafiltration permits to determine alpha-2 macroglobulin bound zinc and losely bound zinc if a strong
zinc ligand (EDTA) is added to serum before ultrafiltration. This last fraction, after deduction of ultrafiltrable zinc, represents
roughly all albumin bound zinc. In 20 controls we found that ultrafiltrable zinc amounted 0.311 μmol/L (S.D.=0.117 μmol/L),
alpha-2 macroglobulin bound zinc 3.08 μmol/L (S.D.=0.221 μmol/L), and albumin bound zinc 12.11 μmol/L (S.D.=1.95 μmol/L).
Our method needs only a small volume of serum, it is simple and rapid but also very accurate and reliable. The losely bound
fraction is very dynamic and, representing the physiologically active part of serum zinc, it could be a good marker of zinc
deficiency. 相似文献
416.
Patrick H. Frémont Félix Crossin Didier Renaud Josiane Fontaine-Pérus 《Differentiation; research in biological diversity》1992,49(1):17-26
Myoblasts from rudiments of slow and fast muscle, anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) respectively, of 9-day-old quail embryos were cultured in vitro for a period of up to 60 days in order to give rise to well-differentiated muscle fibres. These fibres were innervated by neurons from either quail or mouse embryo spinal cord and their innervation pattern was examined by the visualization of acetylcholine receptors (ACh-R) and of acetylcholinesterase (ACh-E) activity at the neuromuscular contacts. In the culture system used, quail neurons always innervated muscle fibres at several sites and only when a fast-type activity was imposed on these neurons did a reduction in the number of the previously established neuromuscular contacts take place. In contrast, in the muscle fibres innervated by mouse neurons, a spontaneous reduction in the number of the previously established neuromuscular contacts occurred but this spontaneous reduction depended upon the level of differentiation reached by the muscle fibres in vitro. In the cultures of muscle fibres previously innervated by mouse neurons, the addition of quail neurons did not provoke any modification in the initial innervation pattern, and no quail ACh-R cluster was observed. In contrast, in the muscle fibres previously innervated by quail neurons, the mouse neurons contacted these fibres, resulting in a decrease in the number of quail ACh-R clusters. These results emphasize the part played by neurons in the establishment of the innervation pattern when muscle fibres have reached a high level of differentiation. In vitro, the slow and fast characteristics of the muscle fibres do not influence this pattern. 相似文献
417.
418.
419.
M. Tamarelle M. L. Sallafranque J. P. Benedetto J. Bonnet J. Vieillemaringe J. Girardie 《Histochemistry and cell biology》1990,95(2):195-203
Summary A tryptophanyl-tRNA synthetase (TrpRS)-immunoreactivity is localized in various neurosecretory cells of all ganglia of the central nervous system of the Orthoptera Locusta migratoria, except in deutocerebrum, and in endocrine cells of the midgut. It has been observed that TrpRS-like material never co-localizes either with CCK-like or octopamine-like material.TrpRS immunoreactive perikarya and processes that ramify extensively throughout the neuropiles have been detected in the protocerebrum, optic lobes, tritocerebrum, suboesophageal, thoracic and abdominal ganglia. In the lateral protocerebrum, a particular TrpRS pathway different from the lateral gastrin cholecystokinin (CCK-8(s)) pathway is revealed, certain of these processes terminating in the glandular part of the corpora cardiaca. In the metathoracic ganglion, have been observed numerous immunoreactive cell bodies and processes in the neuropiles. Some of them constitute a major pathway and which are distinct from octopamine (OA) cells but in close vicinity with the latter. In the midgut immunopositive TrpRS-like cells are dispersed among the regenerative and digestive cells of the epithelium; they are different from gastrin-cholecystokinin positive cells.The various TrpRS-like immunoreactivities identified in Locusta indicate that TrpRS-like material may occur in different tissues of organisms other than Vertebrates. These results suggest also that TrpRS-like enzyme could be involved in functions other than aminoacylation, as in Vertebrates. 相似文献