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131.
132.
Characterization and regulation of the expression of FatB, an iron transport protein encoded by the pJM1 virulence plasmid 总被引:7,自引:0,他引:7
Luis A. Actis Marcelo E. Tolmasky Lidia M. Crosa Jorge H. Crosa 《Molecular microbiology》1995,17(1):197-204
The pJM1-encoded genes fatDCBA are essential for iron acquisition via the siderophore anguibactin. Sequence analysis indicated that the open reading frame corresponding to the fatB gene possesses domains that are characteristic of periplasmic proteins that bind the ferric siderophore. In this work, a monospecific antiserum against an oligopeptide containing the last 27 amino acids of the carboxy-terminal region from this open reading frame was used to demonstrate that fatB encodes a 35 kDa protein that is essential for iron transport. By using this antibody we were able to demonstrate that expression of the fatB gene is negatively regulated by the Fur protein at high iron concentrations. Conversely, its expression was positively regulated by the combined action of the AngR protein and products of the TAF region. FatB, the product of the fatB gene, is isolated with the membrane fraction. In accordance with these findings is the fact that the first 23 amino acid residues of this protein have the properties of a lipoprotein signal sequence. The lipoprotein nature of FatB is supported by the fact that treatment of Vibrio anguillarum cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 38 kDa pro-FatB precursor protein. 相似文献
133.
C. Rohde 《World journal of microbiology & biotechnology》1995,11(3):367-369
The author is with the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Mascheroder Weg 1 B, D-38124 Braunschweig, Germany 相似文献
134.
Location of the active site of the bean {alpha}-amylase inhibitor and involvement of a Trp, Arg, Tyr triad 总被引:1,自引:0,他引:1
Mirkov T.Erik; Evans Stephen V.; Washlstrom Janice; Gomez Luis; Young N.Martin; Chrispeels Maarten J. 《Glycobiology》1995,5(1):45-50
Seeds of the common bean contain three homologous proteins:phytohaemagglutinin E, phytohaemagglutinin L and the lectin-likeprotein 相似文献
135.
Ecology of marine parasites 总被引:2,自引:0,他引:2
K. Rohde 《Helgoland Marine Research》1984,37(1-4):5-33
Important ecological aspects of marine parasites are discussed. Whereas effects of parasites on host individuals sometimes leading to death are known from many groups of parasites, effects on host populations have been studied much less. Mass mortalities have been observed mainly among hosts occurring in abnormally dense populations or after introduction of parasites by man. As a result of large-scale human activities, it becomes more and more difficult to observe effects of parasites on host populations under natural conditions. Particular emphasis is laid on ecological characteristics of parasites, such as host range and specificity, microhabitats, macrohabitats, food, life span, aggregated distribution, numbers and kinds of parasites, pathogenicity and mechanisms of reproduction and infection and on how such characteristics are affected by environment and hosts. It is stressed that host specificity indices which take frequency and/or intensity of infection into account, are a better measure of restriction of parasites to certain hosts than host range which simply is the number of host species found to be infected. 相似文献
136.
Luis Pezzi 《Bioscience reports》1984,4(3):231-237
The rate of ruthenium-red-induced Ca2+ efflux depends on the time that the calcium interacts with the mitochondria prior to the addition of the inhibitor. This time-dependency is abolished in the presence of nupercaine; it does not occur in the case of Sr2+ efflux from mitochondria in which the endogenous Ca2+ has been substituted by strontium (strontium-treated mitochondria, STM). Ruthenium red inhibits the respiratory-inhibitor- or uncoupler-induced Sr2+ efflux from STM, but not the Ca2+ efilux from standard mitochondria. The influence of the calcium-induced mitochondrial damage upon the effect of ruthenium red is discussed. 相似文献
137.
Lelio Orci Michael S. Brown Joseph L. Goldstein Luis M. Garcia-Segura Richard G.W. Anderson 《Cell》1984,36(4):835-845
The crystalloid endoplasmic reticulum (ER) houses large amounts of HMG CoA reductase, the rate-controlling enzyme in cholesterol synthesis. The crystalloid ER appears in UT-1 cells, a line of Chinese hamster ovary cells that has been chronically starved of cholesterol as a result of growth in the presence of compactin, an inhibitor of reductase. When cholesterol was provided to UT-1 cells in the form of low density lipoprotein (LDL), the reductase and crystalloid ER were destroyed. This destruction was preceded by an increase in the cholesterol content of crystalloid ER membranes, as judged by a 4- to 8-fold increase in their ability to form complexes with filipin, a cholesterol-binding compound that can be visualized in freeze-fracture electron micrographs. Filipin binding to other membranes was unchanged. Thus insertion of cholesterol into the crystalloid ER membrane may trigger the degradation of reductase and the membrane itself. 相似文献
138.
Alexander Tschopp Augusto Cogoli Marian L. Lewis Dennis R. Morrison 《Journal of biotechnology》1984,1(5-6)
Attachment to a substrate and survival of human embryonic kidney (HEK) cells have been tested in an incubator installed in the flight-deck of the Space Shuttle ‘Challenger’ during its eighth mission.HEK cells are producing the enzyme urokinase and are presently investigated as candidates for electrophoretic separation in an apparatus developed and manufactured by McDonnell Douglas.Attachment of HEK cells to a substrate is mandatory for survival and production of urokinase after electrophoretic separation.Analysis of the samples shows that cells adhere, spread and survive in microgravity (< 10−3 ×g) conditions as well as the ground controls at 1 × g. This result represents an important step towards further bioprocessing in space. 相似文献
139.
Danley A. S. Callieri Carlos G. Núñez Juan C. Díaz Ricci Luis Scidá 《Applied microbiology and biotechnology》1984,19(4):267-271
Summary
Candida utilis var. major NRRL-Y-1084 was grown in a defined medium without a phosphorous (P) source. During the exponential phase, cells divided according to a specific growth rate of 0.32 h-1, which is lower than the usual rate for a balanced medium (0.4–0.6 h-1). The relative P content of the biomass decreased from 2.70% to 0.75% over a period of 6 h, including 2 h of cell division arrest. At the end of this period there was another interruption of cell division. After that, multiplication restarted at a considerably lower rate and it deviated slightly from the exponential pattern. The stationary phase began when biomass P content reached 0.4%–0.5%, slowly decreasing afterwards to 0.25–0.20%. Biomass synthesis was less affected than cell division by the relative decrease of endogenous P, the two processes differing partially in their kinetics. Cell lysis started shortly before the stationary phase and affected about 20% of the population by the end of the assay. RNA and P content of the resulting biomass were 2.4% and 0.25% respecitvely, P being mainly incorporated to RNA.The relationship of biomass production to glucose uptake was very low, probably because the marked P deficiency called for an increase in energy consumption for growth and specially for maintenance. Compared with yeasts grown in a balanced medium, 40% increase in glycogen was observed, whereas no mean changes in the content of cell wall carbohydrates (glucan and mannan) and that of true protein were found.Member of the Scientific Researcher's Career of the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET). Agrentina 相似文献
140.
The songs of 15 colour-marked, mated pairs of white-crowned sparrows (Zonotrichia leucophrys nuttalli) were recorded in a contact zone between the Presidio and San Francisco, California dialect regions. Males were recorded in the field and females were trapped after the breeding season and injected with testosterone to induce singing. The song of each member of a mated pair was classified using two different markers. It was found that most pairs did not match song types, and that the reproductive success of those that matched did not differ from those that did not match. Most of the territorial males sang the Presidio dialect, while most injected females sang the San Francisco dialect. The results fail to support a positive assortative mating hypothesis regarding the functional significance of learning dialects. It is suggested that the mismatching of songs could be due to sexual differences in the disposition to learn songs of neighbours at the breeding site. 相似文献