共查询到20条相似文献,搜索用时 62 毫秒
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Three sporeless mutants of Bacillus thuringiensis, 2 derived from var. thuringiensis and 1 from var. sotto were selected after mutagenic treatment. They were completely lacking in ability to form spores, yet maintained intact insecticidal activity. 相似文献
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Manuela Ambrosio Francesca Fanelli Silvia Brocchetti Francesco Raimondi Mario Mauri G. Enrico Rovati Valérie Capra 《Cellular and molecular life sciences : CMLS》2010,67(17):2979-2989
In class A GPCRs the E/DRY motif is critical for receptor activation and function. According to experimental and computational
data, R3.50 forms a double salt bridge with the adjacent E/D3.49 and E/D6.30 in helix 6, constraining the receptor in an inactive
state. The disruption of this network of interactions facilitates conformational transitions that generate a signal or constitutive
activity. Here we demonstrate that non-conservative substitution of either E129(3.49) or E240(6.30) of thromboxane prostanoid receptor (TP) resulted in mutants characterized by agonist-induced more efficient signaling properties,
regardless of the G protein coupling. Results of computational modeling suggested a more effective interaction between Gq and the agonist-bound forms of the TP mutants, compared to the wild type. Yet, none of the mutants examined revealed any
increase in basal activity, precluding their classification as constitutively active mutants. Here, we propose that these
alternative active conformations might be identified as superactive mutants or SAM. 相似文献
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R Megnet 《Experientia》1966,22(4):216-218
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The study of Drosophila melanogaster by a combination of forward genetics with specific mutants, and reverse genetics, in which a given gene is expressed in an
appropriate brain area to test its effect on behavior, provides a unique opportunity to explore the causal relationship between
a particular gene, its function in the cell and the behavioral outcome at the organismic level. Enhanced male-to-male courtship
has been shown to occur as a result of mutations in several different genes. For example, the Voila mutant exhibits intense GAL4 reporter expression in the tarsal gustatory sensilla, suggesting the importance of tapping by
a male on the female abdomen with his forelegs. Feminization of parts of the antennal lobe and mushroom body by targeted expression
of a female-determining gene transformer
+ (tra
+) drives the male to court other males. Mutations in the tra target gene fruitless (fru), which is expressed in the antennal lobe as well as the suboesophageal ganglion (the gustatory inputs are processed here),
also induce homosexual courtship in males. These results suggest that sensory inputs mediated and/or processed by the tarsal
receptors, suboesophageal ganglion, antennal lobe and mushroom body contribute to the regulation of male–female courtship.
Mosaic analysis localized the neural center for male courtship behavior to the posterior dorsal brain, in which the sensory
information processed by the aforementioned neural structures may be integrated. Another mosaic study mapped the neural center
for female sexual behavior, as measured by her receptiveness to copulation, to the anterior dorsal brain. The issue as to
how the mutations that reduce female sexual receptiveness, e.g. dissatisfaction (dsf), spinster (spin) and chaste (cht), affect the structure and/or function of this neural center deserves to be addressed urgently.
Received 27 April 1999; received after revision 21 June 1999; accepted 8 July 1999 相似文献
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Prosperi-Meys C de Seny D Llabres G Galleni M Lamotte-Brasseur J 《Cellular and molecular life sciences : CMLS》2002,59(12):2136-2143
Increased resistance to β-lactam antibiotics is mainly due to β-lactamases. X-ray structures of zinc β-lactamases unraveled
the coordination of the metal ions, but their mode of action remains unclear. Recently, enzymes in which one of the zinc ligands
was mutated have been characterized and their catalytic activity against several β-lactam antibiotics measured. A molecular
modeling study of these enzymes was performed here to explain the catalytic activity of the mutants. Coordination around the
zinc ions influences the way the tetrahedral intermediate is bound; any modification influences the first recognition of the
substrate by the enzyme. For all the studied mutants, at least one of the interactions fails, inducing a loss of catalytic
efficiency compared to the wild type. The present studies show that the enzyme cavity is a structure of high plasticity both
structurally and mechanistically and that local modifications may propagate its effects far from the mutated amino
acid.
Received 28 August 2002; received after revision 22 October 2002; accepted 24 October 2002
RID="*"
ID="*"Corresponding author. 相似文献
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A. Vaishampayan 《Cellular and molecular life sciences : CMLS》1985,41(1):137-139
Summary Diuron (DCMU) is inhibitory to the photoautotrophic and photoheterotrophic growth of the N2-fixing blue-green algaNostoc muscorum at concentrations of 1.0×10–5 M and 2.0×10–5 M, respectively. A mutant of this organism resistant to 5.0×10–5 M DCMU under its photoheterotrophic growth conditions, with the ability to utilize DCMU as a carbon and nitrogen source for growth, and complete inability to grow photoautotrophically has been isolated. With the apparent defect in its photosynthetic ability, it is suggested that theDCMU
r mutant lacks the step inhibited by 1.0×10–5 M DCMU, and metabolizes DCMU by an existing enzyme system in the absence of such inhibition. That this enzyme may be glutamine synthetase (GS) is explained with the help of a L-methionine-DL-sulfoximine (MSO)-resistant mutant ofN. muscorum which is able to grow faster with 2.0×10–5 DCMU and is known to contain an altered GS.Thanks are due to the Council of Scientific and Industrial Research, CSIR Complex, Govt. of India, New Delhi-110012, for appointing the author to the Scientists' Pool for undertaking researches on the physiological and genetic controls of nitrogen metabolism in blue-green algae, a part of which is presented in this literature. 相似文献
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Zusammenfassung Aus verschiedenen cytoplasmatischen –) und nuklearen (p) atmungsdefekten Hefemutanten isolierte Mitochondrien weisen eine Aktino-mycin-empfindliche Inkorporation von3H-UTP in die TCS-unlösliche Fraktion auf. Die Absenz der mitochondrialen Proteosynthese dieser Mutanten könnte daher auf einen Hemmer im Translationsmechanismus zurückgeführt werden. 相似文献
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R. D. Miller Cynthia Affolder N. Neuss 《Cellular and molecular life sciences : CMLS》1981,37(9):928-930
Summary The presence of the oxygen atom in place of the sulfur atom has significant impact on the polarity of the -lactam derivative. This has been illustrated by direct comparison of HPLC data of 4 different cephalosporin derivatives and their oxa analogues.Acknowledgment. We gratefully acknowledge the cooperation of Drs Yuji Sendo, Toshiro Konoike, Masayuki Murakami and Mitsuru Yoshioka of Shionogi Research Laboratories, Shionogi and Co., Ltd, Fukushima-ku, Osaka, 553, Japan, who synthesized the oxa--lactams and made them available for this study. 相似文献
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