Distinct modes of signal recognition particle interaction with the ribosome

Signal recognition particle (SRP), together with its receptor (SR), mediates the targeting of ribosome-nascent chain complexes to the endoplasmic reticulum. Using protein cross-linking, we detected distinct modes in the binding of SRP to the ribosome. During signal peptide recognition, SRP54 is positioned at the exit site close to ribosomal proteins L23a and L35. When SRP54 contacts SR, SRP54 is rearranged such that it is no longer close to L23a. This repositioning may allow the translocon to dock with the ribosome, leading to insertion of the signal peptide into the translocation channel.     

Structural basis for tail-anchored membrane protein biogenesis by the Get3-receptor complex

Tail-anchored (TA) proteins are involved in cellular processes including trafficking, degradation, and apoptosis. They contain a C-terminal membrane anchor and are posttranslationally delivered to the endoplasmic reticulum (ER) membrane by the Get3 adenosine triphosphatase interacting with the hetero-oligomeric Get1/2 receptor. We have determined crystal structures of Get3 in complex with the cytosolic domains of Get1 and Get2 in different functional states at 3.0, 3.2, and 4.6 angstrom resolution. The structural data, together with biochemical experiments, show that Get1 and Get2 use adjacent, partially overlapping binding sites and that both can bind simultaneously to Get3. Docking to the Get1/2 complex allows for conformational changes in Get3 that are required for TA protein insertion. These data suggest a molecular mechanism for nucleotide-regulated delivery of TA proteins.     

Aquatic areas of ecological importance as inputs into surface water resource protection areas in Zambia

1. Although the network of national parks in Zambia offers a degree of protection for freshwater diversity, the protection status of numerous systems outside of these parks requires further action. The biodiversity associated with its freshwater systems, both lotic and lentic, is unique, covering a climatic gradient from tropical to subtropical across the Zambezi and Congo basins. Recent Zambian legislation allows for the delineation of water resource protection areas (WRPAs), with one of the criteria being that they include aquatic areas of ecological importance (AEIs).
2. In this study, a systematic conservation planning approach was used to identify aquatic AEIs objectively. Importantly, the approach included a rigorous and iterative stakeholder engagement and review process.
3. The conservation planning software marxan was chosen because of its ability to integrate upstream–downstream connectivity. In total, 5,671 planning units (sub-catchments with an average area of approx. 14,000 ha) were populated with 77 biodiversity features: data were drawn from a wide range of sources, and included fishes, semi-aquatic mammals, molluscs, amphibians, and ecotonal physiographic features, such as waterfalls. Sub-catchments were preferentially chosen using a combination of area- and distance-weighted boundary costs.
4. The final solution highlights critical clusters in each of the major freshwater ecoregions in Zambia, with all conservation targets being met. Results show that although the existing protected area network also coincides with identified aquatic AEIs, approximately 80% of all aquatic AEIs fall outside of formally protected areas.
5. The outcomes of this process serve as one of three prioritization layers (the other two being water provision and sensitivity to human impacts) that are integrated in a larger study to select and prioritize WRPAs.

     

Chemical constituents of Hypogymnia enteromorpha

The lichenHypogymnia enteromorpha (Ach.) Nyl. was sequentially extracted by a solvent series that ranged from non-polar to highly polar liquids. The principal extracellular lichen products isolated from this species were thiophaninic acid, physodalic acid, physodic acid, atranorin, and ventosic acid. The carbohydrate D-arabitol was isolated from the more polar extracts. The isolated constituents were identified by means of mixed melting points, specific color tests, thin layer chromatographic R_f values, infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. Quantitative estimates of the amounts of these lichen constituents present in the plant are presented. Three components, thiophaninic acid, ventosic acid, and D-arabitol are here reported for the first time to be constituents of this lichen.

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Zusammenfassung Die FlechteHypogymnia enteromorpha (Ach.) Nyl. wurde stufenweise mit mehreren Lösungsmitteln extrahiert, die in ihren Zusammensetzungen von unpolar bis zu hochpolar reichten. Die wichtigsten extrazellularen Produkte, die von dieser Flechtenspezies isoliert wurden waren Thiophaninsäure, Physodalsäure, Physodsäure, Atranorin und Ventossäure. Das Kohlenhydrat D-arabit wurde von den etwas mehr polaren Extrakten isoliert. Die isolierten Bestandteile wurden durch Mischungsschmelzpunkte, spezifische Farbproben, dünnschicht-chromatographische R_f-Werte, Infrarotspektroskopie, NMR-Spektroskopie, Massenspektrometrie und Elementaranalyse identifiziert. Quantitative Bestimmungen erfolgten hinsichtlich der Flechten-Bestandteile. Die drei Verbindungen Thiophaninsäure, Ventossäure und D-arabit werden hier zum erstenmal als Bestandteile dieser Flechte beschrieben.

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Résumé On a soumis le lichenHypogymnia enteromorpha (Ach.) Nyl. à une séquence d'extractions à l'aide d'une série de solvants comprenant des liquides de nature non-polaire jusqu'à très polaire. Les principaux produits extracellulaires de lichen isolés de cette espèce comprennent l'acide thiophéninique, l'acide physodalique, l'acide physodique, l'atranorine et l'acide ventosique. On a isolé l'hydrate de carbone D-arabitol parmi des solvants de haute polarité. L'identification des constituants se fit à l'aide des points de fusions, les épreuves colorimetriques spécifiques, les valeurs R_f de chromatographie sur couche mince, la spectroscopie infrarouge, la spectrometrie de masse et l'analyse élémentaire. Des évaluations quantitatives du niveau de ces composants de lichen présents dans cette plante sont presentées. Trois composés, l'acide thiophaninique, l'acide ventosique et le D-arabitol sont rapportés ici pour la première fois comme constituants de ce lichen.

     

The Japanese keiretsu system——A special kind of business relations and corporate governance is changing in a globalizing world

1.Structure of the keiretsu The name keiretsu(in Japanese.系列) means literally "system"," series" or "line".Keiretsu are groups of companies with very close business relations(Munich Business School,2008).The core of these conglomerates is a bank which provides them with liquidity or loans and