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991.
Identification of Heparin-Binding Domains in the Amyloid Precursor Protein of Alzheimer's Disease by Deletion Mutagenesis and Peptide Mapping 总被引:3,自引:0,他引:3
Heidi J. Clarris Roberto Cappai Damien Heffernan Konrad Beyreuther Colin L. Masters David H. Small 《Journal of neurochemistry》1997,68(3):1164-1172
Abstract: Recent studies have shown that the binding of the amyloid protein precursor (APP) of Alzheimer's disease to heparan sulfate proteoglycans (HSPGs) can modulate a neurite outgrowth-promoting function associated with APP. We used three different approaches to identify heparin-binding domains in APP. First, as heparin-binding domains are likely to be within highly folded regions of proteins, we analyzed the secondary structure of APP using several predictive algorithms. This analysis showed that two regions of APP695 contain a high degree of secondary structure, and clusters of basic residues, considered mandatory for heparin binding, were found principally within these regions. To determine which domains of APP bind heparin, deletion mutants of APP695 were prepared and analyzed for binding to a heparin affinity column. The results suggested that there must be at least two distinct heparin-binding regions in APP. To identify novel heparin-binding regions, peptides homologous to candidate heparin-binding domains were analyzed for their ability to bind heparin. These experiments suggested that APP contains at least four heparin-binding domains. The presence of more than one heparin-binding domain on APP suggests the possibility that APP may interact with more than one type of glycosaminoglycan. 相似文献
992.
Tubulin Subunits Exist in an Activated Conformational State Generated and Maintained by Protein Cofactors 总被引:11,自引:1,他引:10
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Guoling Tian Sally A. Lewis Becket Feierbach Timothy Stearns Heidi Rommelaere Christophe Ampe Nicholas J. Cowan 《The Journal of cell biology》1997,138(4):821-832
The production of native α/β tubulin heterodimer in vitro depends on the action of cytosolic chaperonin and several protein cofactors. We previously showed that four such cofactors (termed A, C, D, and E) together with native tubulin act on β-tubulin folding intermediates generated by the chaperonin to produce polymerizable tubulin heterodimers. However, this set of cofactors generates native heterodimers only very inefficiently from α-tubulin folding intermediates produced by the same chaperonin. Here we describe the isolation, characterization, and genetic analysis of a novel tubulin folding cofactor (cofactor B) that greatly enhances the efficiency of α-tubulin folding in vitro. This enabled an integrated study of α- and β-tubulin folding: we find that the pathways leading to the formation of native α- and β-tubulin converge in that the folding of the α subunit requires the participation of cofactor complexes containing the β subunit and vice versa. We also show that sequestration of native α-or β-tubulins by complex formation with cofactors results in the destabilization and decay of the remaining free subunit. These data demonstrate that tubulin folding cofactors function by placing and/or maintaining α-and β-tubulin polypeptides in an activated conformational state required for the formation of native α/β heterodimers, and imply that each subunit provides information necessary for the proper folding of the other. 相似文献
993.
Daniel F. Mazerolle Kevin W. Dufour Keith A. Hobson Heidi E. den Haan 《Journal of avian biology》2005,36(2):155-163
Migrant songbirds are vulnerable to changes in climatic conditions on both the breeding and wintering grounds. For North American Neotropical migrants, the El Niño/Southern Oscillation (ENSO), via its effects on global precipitation and temperature, modulates the productivity of their temperate and tropical terrestrial ecosystems used during the course of their annual cycle. We evaluated how a densely nesting population of yellow warblers Dendroica petechia in a riparian forest in southern Manitoba, Canada, responded to the El Niño/Southern Oscillation (ENSO) between 1992 and 2001. Standardized mist netting was used to estimate apparent annual survival of adults and production of young. Both adult survival and the production of young were positively correlated with the Southern Oscillation Index (SOI). More specifically, values of both these demographic parameters were lowest during El Niño years and highest during La Niña years. These findings demonstrate the influence of climate on populations of Neotropical migrants in North America. The more frequent El Niños predicted to result from future global climate change could negatively affect populations of yellow warblers and other Neotropical migrants breeding in this region. 相似文献
994.
Identification and Stereospecificity of the First Three Enzymes
of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte
Alga 总被引:1,自引:0,他引:1
Peter S. Summers Kurt D. Nolte Arthur J.L. Cooper Heidi Borgeas Thomas Leustek David Rhodes Andrew D. Hanson 《Plant physiology》1998,116(1):369-378
Many marine algae produce 3-dimethylsulfoniopropionate (DMSP), a potent osmoprotective compound whose degradation product dimethylsulfide plays a central role in the biogeochemical S cycle. Algae are known to synthesize DMSP via the four-step pathway, l-Met → 4-methylthio-2-oxobutyrate → 4-methylthio-2-hydroxybutyrate → 4-dimethylsulfonio-2-hydroxy-butyrate (DMSHB) → DMSP. Substrate-specific enzymes catalyzing the first three steps in this pathway were detected and partially characterized in cell-free extracts of the chlorophyte alga Enteromorpha intestinalis. The first is a 2-oxoglutarate-dependent aminotransferase, the second an NADPH-linked reductase, and the third an S-adenosylmethionine-dependent methyltransferase. Sensitive radiometric assays were developed for these enzymes, and used to show that their activities are high enough to account for the estimated in vivo flux from Met to DMSP. The activities of these enzymes in other DMSP-rich chlorophyte algae were at least as high as those in E. intestinalis, but were ≥20-fold lower in algae without DMSP. The reductase and methyltransferase were specific for the d-enantiomer of 4-methylthio-2-hydroxybutyrate in vitro, and both the methyltransferase step and the step(s) converting DMSHB to DMSP were shown to prefer d-enantiomers in vivo. The intermediate DMSHB was shown to act as an osmoprotectant, which indicates that the first three steps of the DMSP synthesis pathway may be sufficient to confer osmotolerance. 相似文献
995.
Michael Bölker Heidi U. Böhnert Karl Heinz Braun Johannes Görl Regine Kahmann 《Molecular genetics and genomics : MGG》1995,248(5):547-552
In the maize pathogenic fungusUstilago maydis integration of transforming DNA at homologous or heterologous sites is often accompanied by duplications of the DNA. We show that it is possible to generate single-copy integration events with high efficiency by restriction enzyme-mediated integration (REMI). In about 50% of cases, a plasmid that contains a singleBamHI site is integrated at chromosomalBamHI sites, ifBamHI is added to the transformation mixtures. In the other cases it appears that integration events have also occurred preferentially atBamHI sites, but without restoration of the recognition sites. Using REMI we have generated approximately 1000 insertion mutants. Pathogenicity tests demonstrated that about 1–2% of these mutants were unable to induce symptoms when testedin planta. For two of the mutants we have shown that the phenotype is linked to the insertion event. 相似文献
996.
Chronic caloric restriction (CR) prevents the development of obesity and maintains health, slows aging processes, and prevents or substantially delays the development of non-insulin-dependent diabetes. Because changes in energy metabolism could be involved in all of these positive effects of CR, we examined glycogen synthase (GS) and glycogen phosphorylase (GP) activities and glucose 6-phosphate (G6P) and glycogen concentrations in skeletal muscle samples before and during a euglycemic hyperinsulinemic clamp in 6 older aged monkeys in which CR had been continued for 10.4 ± 2.1 years. Basal GS activity (fractional velocity and independent) was significantly higher in the CR monkeys than has been previously shown in normal, hyperinsulinemic and diabetic monkeys. The normal effect of insulin to activate GS was absent in the CR group due to the paradoxical finding in some of these monkeys of a reduction in GS activity by insulin. Insulin also had the unexpected effect of increasing the independent activity of GP above basal activity (p<0.05). There was an inverse relationship between the change (insulin-stimulated minus basal) in GS fractional velocity and GP activity ratio (r=-0.91, p<0.005). The basal independent activities of GS and GP were also inversely correlated (r=-0.79, p<0.05). The insulin-stimulated concentration of G6P tended to be higher than the basal concentration (p<0.06) and was significantly higher than that previously shown in normal monkeys (p<0.05). We suggest that long-term calorie restriction (1) results in alterations in glycogen metabolism that may be important to the anti-diabetogenic and anti-aging effects of CR and (2) unmasks early defects which may indicate the likelihood of ultimately developing obesity and diabetes. 相似文献
997.
Anders Galatius Mai-Britt Elin Rindom Andersen Birgitte Haugan Heidi Elisabeth Langhoff Åse Jespersen 《Acta zoologica》2006,87(1):77-82
Epiphyseal development was investigated on X‐rays of flippers from 158 harbour porpoises from Danish waters. Development followed a proximodistal pattern similar to what is known in other cetacean species. Ossification of epiphyses was rare in the phalanges of the first and fifth digits and in the more distal phalanges of the second, third and fourth digits. Along with the morphology of the first metacarpal and the more distal phalanges this suggested paedomorphosis relative to delphinids. Male and female porpoises showed similar progression of epiphyseal development until approximately the sixth year. From then on, female porpoises showed more progressed development than males. This suggests a higher level of paedomorphosis in the male porpoise. The mechanism behind phocoenid paedomorphosis seems to be progenesis, probably as an adaptation towards a high reproductive rate relative to the delphinids. 相似文献
998.
Summary The cells of Halobacterium sp., strain 5, contain a large number of highly refractile bodies of the type which Petter (1932) suggested were gas-filled vacuoles. The present studies support Petter's contention, but the evidence for the exact chemical nature of the vacuole content is still indirect. It is not carbon dioxide or oxygen, but might possibly be nitrogen. Strain 5 loses spontaneously and with a high frequency the ability to make the vacuoles.When vacuolated cells are subjected to pressure, the vacuoles disappear, but can recover upon aeration. Oxygen and the organic constituents of the growth medium stimulate the recovery, whereas 2.4-dinitrophenol inhibits it. A procedure is described for the isolation of the vacuoles. The vacuoles are bounded by a membrane which reveals itself in electron micrographs of thin sections as a 1-layered structure about 30 Å thick.Dedicated to Prof. C. B. van Niel on the occasion of his 70th birthday. 相似文献
999.
Hutabarat Olly Sanny Flachowsky Henryk Regos Ionela Miosic Silvija Kaufmann Christine Faramarzi Shadab Alam Mohammed Zobayer Gosch Christian Peil Andreas Richter Klaus Hanke Magda-Viola Treutter Dieter Stich Karl Halbwirth Heidi 《Planta》2016,243(5):1213-1224
Planta - Overexpression of chalcone-3-hydroxylase provokes increased accumulation of 3-hydroxyphloridzin in Malus . Decreased flavonoid concentrations but unchanged flavonoid class composition were... 相似文献
1000.
Finn Cilius Nielsen Heidi Theil Hansen Jan Christiansen 《BioEssays : news and reviews in molecular, cellular and developmental biology》2016,38(7):674-681
Eukaryotic mRNAs are monocistronic, and therefore mechanisms exist that coordinate the synthesis of multiprotein complexes in order to obtain proper stoichiometry at the appropriate intracellular locations. RNA‐binding proteins containing low‐complexity sequences are prone to generate liquid droplets via liquid‐liquid phase separation, and in this way create cytoplasmic assemblages of functionally related mRNAs. In a recent iCLIP study, we showed that the Drosophila RNA‐binding protein Imp, which exhibits a C‐terminal low‐complexity sequence, increases the formation of F‐actin by binding to 3′ untranslated regions of mRNAs encoding components participating in F‐actin biogenesis. We hypothesize that phase transition is a mechanism the cell employs to increase the local mRNA concentration considerably, and in this way synchronize protein production in cytoplasmic territories, as discussed in the present review. 相似文献