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101.
Lemaire K Moura RF Granvik M Igoillo-Esteve M Hohmeier HE Hendrickx N Newgard CB Waelkens E Cnop M Schuit F 《PloS one》2011,6(4):e18517
UFM1 is a member of the ubiquitin like protein family. While the enzymatic cascade of UFM1 conjugation has been elucidated in recent years, the biological function remains largely unknown. In this report we demonstrate that the recently identified C20orf116, which we name UFM1-binding protein 1 containing a PCI domain (UFBP1), and CDK5RAP3 interact with UFM1. Components of the UFM1 conjugation pathway (UFM1, UFBP1, UFL1 and CDK5RAP3) are highly expressed in pancreatic islets of Langerhans and some other secretory tissues. Co-localization of UFM1 with UFBP1 in the endoplasmic reticulum (ER) depends on UFBP1. We demonstrate that ER stress, which is common in secretory cells, induces expression of Ufm1, Ufbp1 and Ufl1 in the beta-cell line INS-1E. siRNA-mediated Ufm1 or Ufbp1 knockdown enhances apoptosis upon ER stress. Silencing the E3 enzyme UFL1, results in similar outcomes, suggesting that UFM1-UFBP1 conjugation is required to prevent ER stress-induced apoptosis. Together, our data suggest that UFM1-UFBP1 participate in preventing ER stress-induced apoptosis in protein secretory cells. 相似文献
102.
Novel Bacterial Membrane Surface Display System Using Cell Wall-Less L-Forms of Proteus mirabilis and Escherichia coli 总被引:2,自引:0,他引:2 下载免费PDF全文
Christian Hoischen Christine Fritsche Johannes Gumpert Martin Westermann Katleen Gura Beatrix Fahnert 《Applied microbiology》2002,68(2):525-531
We describe a novel membrane surface display system that allows the anchoring of foreign proteins in the cytoplasmic membrane (CM) of stable, cell wall-less L-form cells of Escherichia coli and Proteus mirabilis. The reporter protein, staphylokinase (Sak), was fused to transmembrane domains of integral membrane proteins from E. coli (lactose permease LacY, preprotein translocase SecY) and P. mirabilis (curved cell morphology protein CcmA). Both L-form strains overexpressed fusion proteins in amounts of 1 to 100 μg ml−1, with higher expression for those with homologous anchor motifs. Various experimental approaches, e.g., cell fractionation, Percoll gradient purification, and solubilization of the CM, demonstrated that the fusion proteins are tightly bound to the CM and do not form aggregates. Trypsin digestion, as well as electron microscopy of immunogold-labeled replicas, confirmed that the protein was localized on the outside surface. The displayed Sak showed functional activity, indicating correct folding. This membrane surface display system features endotoxin-poor organisms and can provide a novel platform for numerous applications. 相似文献
103.
β-Barrel proteins, or outer membrane proteins (OMPs), perform many essential functions in Gram-negative bacteria, but questions remain about the mechanism by which they are assembled into the outer membrane (OM). In Escherichia coli, β-barrels are escorted across the periplasm by chaperones, most notably SurA and Skp. However, the contributions of these two chaperones to the assembly of the OM proteome remained unclear. We used differential proteomics to determine how the elimination of Skp and SurA affects the assembly of many OMPs. We have shown that removal of Skp has no impact on the levels of the 63 identified OM proteins. However, depletion of SurA in the skp strain has a marked impact on the OM proteome, diminishing the levels of almost all β-barrel proteins. Our results are consistent with a model in which SurA plays a primary chaperone role in E. coli. Furthermore, they suggest that while no OMPs prefer the Skp chaperone pathway in wild-type cells, most can use Skp efficiently when SurA is absent. Our data, which provide a unique glimpse into the protein content of the nonviable surA skp mutant, clarify the roles of the periplasmic chaperones in E. coli. 相似文献
104.
Aaike De Wever Frederik Leliaert Elie Verleyen Pieter Vanormelingen Katleen Van der Gucht Dominic A. Hodgson Koen Sabbe Wim Vyverman 《Proceedings. Biological sciences / The Royal Society》2009,276(1673):3591-3599
Recent data revealed that metazoans such as mites and springtails have persisted in Antarctica throughout several glacial–interglacial cycles, which contradicts the existing paradigm that terrestrial life was wiped out by successive glacial events and that the current inhabitants are recent colonizers. We used molecular phylogenetic techniques to study Antarctic microchlorophyte strains isolated from lacustrine habitats from maritime and continental Antarctica. The 14 distinct chlorophycean and trebouxiophycean lineages observed point to a wide phylogenetic diversity of apparently endemic Antarctic lineages at different taxonomic levels. This supports the hypothesis that long-term survival took place in glacial refugia, resulting in a specific Antarctic flora. The majority of the lineages have estimated ages between 17 and 84 Ma and probably diverged from their closest relatives around the time of the opening of Drake Passage (30–45 Ma), while some lineages with longer branch lengths have estimated ages that precede the break-up of Gondwana. The variation in branch length and estimated age points to several independent but rare colonization events. 相似文献
105.
Katleen Denoncin Didier Vertommen Isabelle S. Arts Camille V. Goemans Sophie Rahuel-Clermont Joris Messens Jean-Fran?ois Collet 《The Journal of biological chemistry》2014,289(18):12356-12364
We report a new function for Escherichia coli DsbC, a protein best known for disulfide bond isomerization in the periplasm. We found that DsbC regulates the redox state of the single cysteine of the l-arabinose-binding protein AraF. This cysteine, which can be oxidized to a sulfenic acid, mediates the formation of a disulfide-linked homodimer under oxidative stress conditions, preventing l-arabinose binding. DsbC, unlike the homologous protein DsbG, reduces the intermolecular disulfide, restoring AraF binding properties. Thus, our results reveal a new link between oxidative protein folding and the defense mechanisms against oxidative stress. 相似文献
106.
Relationship between bacterial community composition and bottom-up versus top-down variables in four eutrophic shallow lakes 总被引:5,自引:0,他引:5
Muylaert K Van Der Gucht K Vloemans N Meester LD Gillis M Vyverman W 《Applied and environmental microbiology》2002,68(10):4740-4750
Bacterial community composition was monitored in four shallow eutrophic lakes during one year using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified prokaryotic rDNA genes. Of the four lakes investigated, two were of the clearwater type and had dense stands of submerged macrophytes while two others were of the turbid type characterized by the occurrence of phytoplankton blooms. One turbid and one clearwater lake had high nutrient levels (total phosphorus, >100 micro g liter(-1)) while the other lakes had relatively low nutrient levels (total phosphorus, <100 micro g liter(-1)). For each lake, seasonal changes in the bacterial community were related to bottom-up (resources) and top-down (grazers) variables by using canonical correspondence analysis (CCA). Using an artificial model dataset to which potential sources of error associated with the use of relative band intensities in DGGE analysis were added, we found that preferential amplification of certain rDNA genes over others does not obscure the relationship between bacterial community composition and explanatory variables. Besides, using this artificial dataset as well as our own data, we found a better correlation between bacterial community composition and explanatory variables by using relative band intensities compared to using presence/absence data. While bacterial community composition was related to phytoplankton biomass in the high-nutrient lakes no such relation was found in the low-nutrient lakes, where the bacterial community is probably dependent on other organic matter sources. We used variation partitioning to evaluate top-down regulation of bacterial community composition after bottom-up regulation has been accounted for. Using this approach, we found no evidence for top-down regulation of bacterial community composition in the turbid lakes, while grazing by ciliates and daphnids (Daphnia and Ceriodaphnia) was significantly related to changes in the bacterial community in the clearwater lakes. Our results suggest that in eutrophic shallow lakes, seasonality of bacterial community structure is dependent on the dominant substrate source as well as on the food web structure. 相似文献
107.
Tadesse Dejenie Tsehaye Asmelash Luc De Meester Afework Mulugeta Abreha Gebrekidan Sarah Risch Annemie Pals Katleen Van der Gucht Wim Vyverman Jan Nyssen Jozef Deckers Steven Declerck 《Hydrobiologia》2008,610(1):193-209
The semi-arid highlands of Northern Ethiopia (Tigray) have numerous small reservoirs that have been created by microdams in
an attempt to provide water supply for irrigation and livestock drinking. Although the reservoirs have substantial added value
to residents, their use as water resource is jeopardized by eutrophication and a high occurrence of blooms of toxic cyanobacteria.
So far, there is no systematic information available on the limnological and aquatic ecological characteristics of these dams.
We carried out a standardized survey of 32 reservoirs and assessed a wide set of morphometric, abiotic and biotic variables.
The sampling was performed during two seasons, September–October 2004 (end of the wet season/start of the dry season) and
April–May 2005 (towards the end of the dry season). Using multivariate analysis, we revealed dominating patterns of variable
associations and compared the variability in these patterns among seasons. According to standardized PCA and RDA analyses,
the most important axis of variation was mainly represented by a gradient in nutrients and altitude that was also positively
associated with phytoplankton biomass, suspended matter and oxygen concentration, and negatively with water transparency.
For most variables, correlations between the wet and dry season were weak, which suggests that individual reservoirs behaved
rather differently in their response to seasonal changes. Nevertheless, a Mantel correlation (r = 0.32; P = 0.035) showed a weak but significant overall concordance in the variable association patterns among seasons. A number of
reservoirs became very shallow or fell dry in the dry season, a process that was associated with an increase in suspended
matter and conductivity and a decrease in transparency. These reservoirs contained lower amounts of fish and tended to be
less eutrophic than the deeper, permanent systems, as they had lower levels of phosphorus and chlorophyll-a. With multiple regression analysis, we constructed most parsimonious models in an attempt to explain the variation in key
biotic variables: phytoplankton and cyanobacteria biomass, cladoceran biomass, fish biomass and the abundance of submerged
vegetation. Phytoplankton and fish biomass tended to be positively related with the concentration of total phosphorus, whereas
cladoceran biomass was not associated with nutrient concentrations. The positive association of fish and phytoplankton with
nutrient concentrations suggests a bottom-up control, whereas the absence of an association between zooplankton and nutrient
concentrations may be indicative for top-down control. The biomass of cyanobacteria was negatively related to the biomass
of cladocerans (Daphnia), which likely reflects a top-down effect. Most reservoirs were turbid. The occurrence and abundance of macrophytes tended
to be positively related to water transparency and was negatively associated to TP and the amount of livestock frequenting
the reservoirs. However, macrophytes were not limited to clear-water reservoirs.
Handling editor: L. M. Bini 相似文献
108.
109.
Chemical signalling in lizards: an interspecific comparison of femoral pore numbers in Lacertidae 下载免费PDF全文
Simon Baeckens Shelley Edwards Katleen Huyghe Raoul Van Damme 《Biological journal of the Linnean Society. Linnean Society of London》2015,114(1):44-57
Animals communicate via a variety of sensory channels and signals. Studies on acoustic and visual communication systems suggest that differences in the physical environment contribute to the variety of signalling behaviour, with species investing in those signals that are transmitted best under the local conditions. Whether or not environmental tuning also occurs in chemical communication systems has received much less attention. In the present study, we examined the effect of several aspects of the physical environment on the chemical communication system of lacertid lizards (family Lacertidae). The numbers of femoral pores are used as a proxy reflecting how much a particular species invests in and relies upon chemical signalling. Femoral pores are specialized epidermal structures that function as a secretion channel for the waxy substance produced by glands. In some lacertid species, the secretion carries infochemicals that play an important role in social communication. The number of femoral pores varies considerably among species. We have compiled data on femoral pore numbers for 162 species and tested for the effects of climate and substrate use. After correcting for body size and taking the phylogenetic relationships among the species into account, we found no effect of climate conditions or latitude on species pore numbers. Substrate use did affect pore numbers: shrub‐climbing species tended to have fewer femoral pores than species inhabiting other substrates. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114 , 44–57. 相似文献
110.
Verreydt D De Meester L Decaestecker E Villena MJ Van Der Gucht K Vannormelingen P Vyverman W Declerck SA 《Ecology letters》2012,15(3):218-226
Dispersal is a major organising force in metacommunities, which may facilitate compositional responses of local communities to environmental change and affect ecosystem function. Organism groups differ widely in their dispersal abilities and their communities are therefore expected to have different adaptive abilities. In mesocosms, we studied the simultaneous compositional response of three plankton communities (zoo-, phyto- and bacterioplankton) to a primary productivity gradient and evaluated how this response was mediated by dispersal intensity. Dispersal enhanced responses in all three planktonic groups, which also affected ecosystem functioning. Yet, variation partitioning analyses indicated that responses in phytoplankton and bacterial communities were not only controlled by dispersal directly but also indirectly through complex trophic interactions. Our results indicate that metacommunity patterns emerging from dispersal can cascade through the food web and generate patterns of apparent dispersal limitation in organisms at other trophic levels. 相似文献