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151.
Phosphatidylethanolamine critically supports internalization of cell-penetrating protein C inhibitor 下载免费PDF全文
Baumgärtner P Geiger M Zieseniss S Malleier J Huntington JA Hochrainer K Bielek E Stoeckelhuber M Lauber K Scherfeld D Schwille P Wäldele K Beyer K Engelmann B 《The Journal of cell biology》2007,179(4):793-804
Although their contribution remains unclear, lipids may facilitate noncanonical routes of protein internalization into cells such as those used by cell-penetrating proteins. We show that protein C inhibitor (PCI), a serine protease inhibitor (serpin), rapidly transverses the plasma membrane, which persists at low temperatures and enables its nuclear targeting in vitro and in vivo. Cell membrane translocation of PCI necessarily requires phosphatidylethanolamine (PE). In parallel, PCI acts as a lipid transferase for PE. The internalized serpin promotes phagocytosis of bacteria, thus suggesting a function in host defense. Membrane insertion of PCI depends on the conical shape of PE and is associated with the formation of restricted aqueous compartments within the membrane. Gain- and loss-of-function mutations indicate that the transmembrane passage of PCI requires a branched cavity between its helices H and D, which, according to docking studies, precisely accommodates PE. Our findings show that its specific shape enables cell surface PE to drive plasma membrane translocation of cell-penetrating PCI. 相似文献
152.
Like many invertebrate herbivores, Daphnia frequently face diets with excess carbon (C) relative to elements like phosphorus (P), and with limited ability to store
C-rich compounds. To cope with this relative surplus of C they may either regulate the net uptake of C or dispose of excess
assimilated C via increased release of dissolved organic carbon or CO2. Here we investigate whether juvenile Daphnia magna use respiration as a means of stoichiometrically regulating excess C. Growth rate and respiration were measured under different
algal food qualities (P-replete and P-depleted algae). Growth rate was strongly reduced by P-depleted food, implying a stoichiometric
disposal of excess ingested C. Respiration rates of feeding animals were measured after short- (0.5 h), medium- (12 h) and
long- (five days) term acclimation to P-limited food. The respiration rates of animals during active feeding were not affected
by the acclimation period per se, whereas food quality had a significant effect; respiration rates of feeding animals increased
slightly in individuals receiving low-P food under all acclimation regimes. Respiration was also measured on nonfeeding and
fasting animals that had been acclimated for five days to P-limited food. Respiration rates of these animals were strongly
affected by feeding conditions but not by food quality; feeding individuals had higher respiration rates than those deprived
of food, which again had higher respiration than fasting animals. Although animals grown on low-P food had strongly reduced
growth and thus were expected to have decreased respiration rates due to reduced growth-related costs, this seems to be canceled
out by increased stoichiometric respiration under P-deficiency. These results indicate that D. magna partly releases excess C as CO2, but other means of stoichiometric regulation most likely add to this. 相似文献
153.
Floodplains represent ecotones with frequent high productivity mediated by regular shifts between aquatic and terrestrial
ecosystems. We examined interaction along this intercept on a seasonal floodplain of the Okavango Delta, Botswana. We focused
on the zooplankton communities in order to gain knowledge on the energetic and stoichiometric interplay of the two systems
involved. A conspicuous horizontal migration and pulsed biomass increase was found for the dominant zooplankton species (Moina micrura, Daphnia laevis, Mesocyclops leuckarti), culminating in truly extreme numbers before a final collapse. There was a distinct succession in the peak abundance of
these species, apparently subsidized by hatchlings from the seed bank of resting eggs as the flood proceeded over the savannah.
The high productivity of the system seems to be driven by a strong coupling of the terrestrial and aquatic phase of the floodplains
via a mobilization of terrestrially derived nutrients, through nutrients from grazing ungulates during dry periods. Carbon
of terrestrial origin, however, appeared to be of minor importance for the planktonic part of the food web.
Handling editor: S. Dodson 相似文献
154.
Logares R Rengefors K Kremp A Shalchian-Tabrizi K Boltovskoy A Tengs T Shurtleff A Klaveness D 《Microbial ecology》2007,53(4):549-561
The agents driving the divergence and speciation of free-living microbial populations are still largely unknown. We investigated
the dinoflagellate morphospecies Scrippsiella hangoei and Peridinium aciculiferum, which abound in the Baltic Sea and in northern temperate lakes, respectively. Electron microscopy analyses showed significant
interspecific differences in the external cellular morphology, but a similar plate pattern in the characteristic dinoflagellate
armor. Experimentally, S. hangoei grew in a wide range of salinities (0–30), whereas P. aciculiferum only grew in low salinities (0–3). Despite these phenotypic differences and the habitat segregation, molecular analyses showed
identical ribosomal DNA sequences (ITS1, ITS2, 5.8S, SSU, and partial LSU) for both morphospecies. Yet, a strong interspecific
genetic isolation was indicated by amplified fragment length polymorphism (F
ST = 0.76) and cytochrome b (cob) sequence divergence (∼1.90%). Phylogenetic reconstructions based on ribosomal (SSU, LSU) and mitochondrial (cob) DNA indicated a recent marine ancestor for P. aciculiferum. In conclusion, we suggest that the lacustrine P. aciculiferum and the marine-brackish S. hangoei diverged very recently, after a marine–freshwater transition that exposed the ancestral populations to different selective
pressures. This hypothetical scenario agrees with mounting data indicating a significant role of natural selection in the
divergence of free-living microbes, despite their virtually unrestricted dispersal capabilities. Finally, our results indicate
that identical ITS rDNA sequences do not necessarily imply the same microbial species, as commonly assumed. 相似文献
155.
156.
157.
Inga Eichhorn Katrin Heidemanns Torsten Semmler Bianca Kinnemann Alexander Mellmann Dag Harmsen Muna F. Anjum Herbert Schmidt Angelika Fruth Peter Valentin-Weigand Jürgen Heesemann Sebastian Suerbaum Helge Karch Lothar H. Wieler 《Applied and environmental microbiology》2015,81(20):7041-7047
Enterohemorrhagic Escherichia coli (EHEC) is the causative agent of bloody diarrhea and extraintestinal sequelae in humans, most importantly hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Besides the bacteriophage-encoded Shiga toxin gene (stx), EHEC harbors the locus of enterocyte effacement (LEE), which confers the ability to cause attaching and effacing lesions. Currently, the vast majority of EHEC infections are caused by strains belonging to five O serogroups (the “big five”), which, in addition to O157, the most important, comprise O26, O103, O111, and O145. We hypothesize that these four non-O157 EHEC serotypes differ in their phylogenies. To test this hypothesis, we used multilocus sequence typing (MLST) to analyze a large collection of 250 isolates of these four O serogroups, which were isolated from diseased as well as healthy humans and cattle between 1952 and 2009. The majority of the EHEC isolates of O serogroups O26 and O111 clustered into one sequence type complex, STC29. Isolates of O103 clustered mainly in STC20, and most isolates of O145 were found within STC32. In addition to these EHEC strains, STC29 also included stx-negative E. coli strains, termed atypical enteropathogenic E. coli (aEPEC), yet another intestinal pathogenic E. coli group. The finding that aEPEC and EHEC isolates of non-O157 O serogroups share the same phylogeny suggests an ongoing microevolutionary scenario in which the phage-encoded Shiga toxin gene stx is transferred between aEPEC and EHEC. As a consequence, aEPEC strains of STC29 can be regarded as post- or pre-EHEC isolates. Therefore, STC29 incorporates phylogenetic information useful for unraveling the evolution of EHEC. 相似文献
158.
Hanna Helgeland Simen Rød Sandve Jacob Seilø Torgersen Mari Kyllesø Halle Hilde Sundvold Stig Omholt Dag Inge Våge 《Gene》2014
In mammals, two carotenoid cleaving oxygenases are known; beta-carotene 15,15′-monooxygenase (BCMO1) and beta-carotene 9′,10′-oxygenase (BCO2). BCMO1 is a key enzyme in vitamin A synthesis by symmetrically cleaving beta-carotene into 2 molecules of all-trans-retinal, while BCO2 is responsible for asymmetric cleavage of a broader range of carotenoids. Here, we show that the Atlantic salmon beta-carotene oxygenase (bco) gene family contains 5 members, three bco2 and two bcmo1 paralogs. Using public sequence databases, multiple bco genes were also found in several additional teleost species. Phylogenetic analysis indicates that bco2a and bco2b originate from the teleost fish specific genome duplication (FSGD or 3R), while the third and more distant paralog, bco2 like, might stem from a prior duplication event in the teleost lineage. The two bcmo1 paralogs (bcmo1 and bcmo1 like) appear to be the result of an ancient duplication event that took place before the divergence of ray-finned (Actinopterygii) and lobe-finned fish (Sarcopterygii), with subsequent nonfunctionalization and loss of one Sarcopterygii paralog. Gene expression analysis of the bcmo1 and bco2 paralogs in Atlantic salmon reveals regulatory divergence with tissue specific expression profiles, suggesting that the beta-carotene oxygenase subtypes have evolved functional divergences. We suggest that teleost fish have evolved and maintained an extended repertoire of beta-carotene oxygenases compared to the investigated Sarcopterygii species, and hypothesize that the main driver behind this functional divergence is the exposure to a diverse set of carotenoids in the aquatic environment. 相似文献
159.
The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity 总被引:2,自引:0,他引:2
Colored dissolved organic matter (CDOM) absorbs a substantial fraction of photosynthetically active radiation (PAR) in boreal lakes. However, few studies have systematically estimated how this light absorption influences pelagic primary productivity. In this study, 75 boreal lakes spanning wide and orthogonal gradients in dissolved organic carbon (DOC) and total phosphorus (TP) were sampled during a synoptic survey. We measured absorption spectra of phytoplankton pigments, CDOM, and non-algal particles to quantify the vertical fate of photons in the PAR region. Area-specific rates of gross primary productivity (PPA) were estimated using a bio-optical approach based on phytoplankton in vivo light absorption and the light-dependent quantum yield of photochemistry in PSII measured by a PAM fluorometer. Subsequently, we calculated the effects of CDOM, DOC, and TP concentration on PPA. CDOM absorbed the largest fraction of PAR in the majority of lakes (mean 56.3%, range 36.9–76.2%), phytoplankton pigments captured a comparatively minor fraction (mean 6.6%, range 2.2–28.2%). PPA estimates spanned from 45 to 993 mg C m?2 day?1 (median 286 mg C m?2 day?1). We found contrasting effects of CDOM (negative) and TP (positive) on PPA. The use of DOC or CDOM as predictors gave very similar results and the negative effect of these variables on PPA can probably be attributed to shading. A future scenario of increased DOC, which is highly correlated with CDOM in these lakes, might impose negative effects on areal primary productivity in boreal lakes. 相似文献
160.