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11.
Processing of viral envelope glycoprotein by the endomannosidase pathway: evaluation of host cell specificity 总被引:4,自引:2,他引:2
Endo-alpha-D-mannosidase is an enzyme involved in N-linked oligosaccharide
processing which through its capacity to cleave the internal linkage
between the glucose-substituted mannose and the remainder of the
polymannose carbohydrate unit can provide an alternate pathway for
achieving deglucosylation and thereby make possible the continued formation
of complex oligosaccharides during a glucosidase blockade. In view of the
important role which has been attributed to glucose on nascent
glycoproteins as a regulator of a number of biological events, we chose to
further define the in vivo action of endomannosidase by focusing on the
well characterized VSV envelope glycoprotein (G protein) which can be
formed by the large array of cell lines susceptible to infection by this
pathogen. Through an assessment of the extent to which the G protein was
converted to an endo-beta-N- acetylglucosaminidase (endo H)-resistant form
during a castanospermine imposed glucosidase blockade, we found that
utilization of the endomannosidase-mediated deglucosylation route was
clearly host cell specific, ranging from greater than 90% in HepG2 and PtK1
cells to complete absence in CHO, MDCK, and MDBK cells, with intermediate
values in BHK, BW5147.3, LLC-PK1, BRL, and NRK cell lines. In some of the
latter group the electrophoretic pattern after endo H treatment suggested
that only one of the two N-linked oligosaccharides of the G protein was
processed by endomannosidase. In the presence of the specific
endomannosidase inhibitor, Glcalpha1-->3(1- deoxy)mannojirimycin, the
conversion of the G protein into an endo H- resistant form was completely
arrested. While the lack of G protein processing by CHO cells was
consistent with the absence of in vitro measured endomannosidase activity
in this cell line, the failure of MDBK and MDCK cells to convert the G
protein into an endo H-resistant form was surprising since these cell lines
have substantial levels of the enzyme. Similarly, we observed that
influenza virus hemagglutinin was not processed in castanospermine-treated
MDCK cells. Our findings suggest that studies which rely on glucosidase
inhibition to explore the function of glucose in controlling such critical
biological phenomena as intracellular movement or quality control should be
carried out in cell lines in which the glycoprotein under study is not a
substrate for endomannosidase action.
相似文献
12.
Margarida RG Maia Lal C Chaudhary Charles S Bestwick Anthony J Richardson Nest McKain Tony R Larson Ian A Graham Robert J Wallace 《BMC microbiology》2010,10(1):52
Background
Health-promoting polyunsaturated fatty acids (PUFA) are abundant in forages grazed by ruminants and in vegetable and fish oils used as dietary supplements, but only a small proportion of PUFA finds its way into meat and milk, because of biohydrogenation in the rumen. Butyrivibrio fibrisolvens plays a major role in this activity. The aim of this study was to investigate the mechanisms by which PUFA affect the growth of B. fibrisolvens, how PUFA are metabolized and the metabolic response to growth in the presence of PUFA. 相似文献13.
A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration 总被引:2,自引:0,他引:2
Boyero L Pearson RG Gessner MO Barmuta LA Ferreira V Graça MA Dudgeon D Boulton AJ Callisto M Chauvet E Helson JE Bruder A Albariño RJ Yule CM Arunachalam M Davies JN Figueroa R Flecker AS Ramírez A Death RG Iwata T Mathooko JM Mathuriau C Gonçalves JF Moretti MS Jinggut T Lamothe S M'Erimba C Ratnarajah L Schindler MH Castela J Buria LM Cornejo A Villanueva VD West DC 《Ecology letters》2011,14(3):289-294
The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback. 相似文献
14.
BRUNO STUDER FRANCO WIDMER JÜRG ENKERLI ROLAND K
LLIKER 《Molecular ecology resources》2006,6(4):1108-1110
Twelve microsatellite markers were isolated from Lolium multiflorum. Allelic variability and cross‐species amplification were assessed on 16 individuals of each of the three grassland species L. multiflorum, Lolium perenne and Festuca pratensis. Cross‐species amplification success was 100% for L. perenne and 83% for F. pratensis. The number of alleles detected ranged from one to 14 with an average of 3.4. While three microsatellite loci were polymorphic in all three species, one marker produced species‐specific alleles in all three species. These microsatellite markers provide a valuable tool for population genetic studies within and among species of the Festuca–Lolium complex. 相似文献
15.
MATTHIAS VOLK PATRICK BUNGENER FRANÇOIS CONTAT MYRTA MONTANI JÜRG FUHRER 《Global Change Biology》2006,12(1):74-83
The sensitivity of seminatural grasslands to ozone (O3) pollution is not well known, in spite of the important function of these common ecosystems for agriculture and nature conservation. A 5‐year field experiment was carried out at a rural, mid‐elevation site at Le Mouret (Switzerland) to investigate the effect of elevated O3 on yield and species composition of a permanent, extensively managed, species‐rich old pasture. Using a free‐air fumigation system, circular plots of 7 m diameter were exposed to either ambient air (control plots) or to air containing O3 of approximately 1.5 × ambient concentrations. The resulting accumulated O3 exposure over the threshold of 40 ppb for one season ranged from 13.3 to 59.5 ppm h in the elevated O3 plots, and from 1.0 to 20.7 ppm h in the control plots. Subplots in each ring were harvested three times each year, and harvested biomass was separated into functional groups (FGs) (grasses, legumes, forbs). Productivity in both treatments decreased over time, but the yield of O3‐exposed plots decreased faster than that of the control plots, with the reduction being twice as large by the end of the fifth season. Compared with the ambient air control, loss in annual dry matter yield was 23% after 5 years. The change in annual biomass production because of O3 stress was accompanied by a change in the fractions of FGs, with the legume fraction showing a strong negative response. Such long‐term effects of O3 stress could have negative implications for the maintenance of biological diversity in rural landscapes across large areas of Europe. The results from this first long‐term experiment show that a moderately elevated O3 level reduces the productivity of intact grasslands during a 5‐year exposure under real field conditions. 相似文献
16.
ANDREA GHIRARDO WERNER HELLER MATTHIAS FLADUNG JÖRG‐PETER SCHNITZLER HILKE SCHROEDER 《Plant, cell & environment》2012,35(12):2192-2207
The indirect defences of plants are comprised of herbivore‐induced plant volatiles (HIPVs) that among other things attract the natural enemies of insects. However, the actual extent of the benefits of HIPV emissions in complex co‐evolved plant‐herbivore systems is only poorly understood. The observation that a few Quercus robur L. trees constantly tolerated (T‐oaks) infestation by a major pest of oaks (Tortrix viridana L.), compared with heavily defoliated trees (susceptible: S‐oaks), lead us to a combined biochemical and behavioural study. We used these evidently different phenotypes to analyse whether the resistance of T‐oaks to the herbivore was dependent on the amount and scent of HIPVs and/or differences in non‐volatile polyphenolic leaf constituents (as quercetin‐, kaempferol‐ and flavonol glycosides). In addition to non‐volatile metabolic differences, typically defensive HIPV emissions differed between S‐oaks and T‐oaks. Female moths were attracted by the blend of HIPVs from S‐oaks, showing significantly higher amounts of (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) and (E)‐β‐ocimene and avoid T‐oaks with relative high fraction of the sesquiterpenes α‐farnesene and germacrene D. Hence, the strategy of T‐oaks exhibiting directly herbivore‐repellent HIPV emissions instead of high emissions of predator‐attracting HIPVs of the S‐oaks appears to be the better mechanism for avoiding defoliation. 相似文献
17.
18.
Control of freshwater fish and crayfish community structure in Taranaki,New Zealand: dams,diadromy or habitat structure? 总被引:3,自引:0,他引:3
1. Freshwater fish and crayfish communities were surveyed along elevational gradients in streams radiating from Mount Taranaki, New Zealand. Six of the 38 streams surveyed had dams or weirs and 32 of the 85 sites were above these barriers. 2. Of the 15 fish and one crayfish species captured, 14 were native. The number of species declined with increasing elevation and distance from the sea. Species richness was also lower above dams even when effects of elevation and distance from the sea were accounted for. 3. Linear regression models using sites without dams were constructed to predict the effect of elevation on fish and crayfish community structure and to allow the effect of dams to be evaluated. The number of species predicted by these models was consistently higher than the number of species found at the above-dam sites. 4. Four fish community groups were classified using two-way indicator species analysis (TWINSPAN). One high elevation group of sites consisted of short steep streams on the west side of the mountain and a second contained longer, lower gradient streams on the east side. The other two groups (3 and 4) consisted of mid-elevation sites and low-elevation sites, respectively. 5. Discriminant analysis was used to predict biotic group membership using the environmental data. Overall, 80% of sites were classified correctly. Correlation of environmental variables with axis scores in the canonical variate analysis revealed that distance from the sea, site elevation and presence of dams were most strongly associated with fish distribution patterns. 相似文献
19.
20.
RENÉ van der WAL SOFIE SJÖGERSTEN† SARAH J. WOODIN† ELISABETH J. COOPER‡ INGIBJÖRG S. JÓNSDÓTTIR‡ DRIES KUIJPER§ TONY A. D. FOX¶ A. D. HUISKES 《Global Change Biology》2007,13(2):539-545
Tundra ecosystems are widely recognized as precious areas and globally important carbon (C) sinks, yet our understanding of potential threats to these habitats and their large soil C store is limited. Land‐use changes and conservation measures in temperate regions have led to a dramatic expansion of arctic‐breeding geese, making them important herbivores of high‐latitude systems. In field experiments conducted in high‐Arctic Spitsbergen, Svalbard, we demonstrate that a brief period of early season belowground foraging by pink‐footed geese is sufficient to strongly reduce C sink strength and soil C stocks of arctic tundra. Mechanisms are suggested whereby vegetation disruption due to repeated use of grubbed areas opens the soil organic layer to erosion and will thus lead to progressive C loss. Our study shows, for the first time, that increases in goose abundance through land‐use change and conservation measures in temperate climes can dramatically affect the C balance of arctic tundra. 相似文献