Parasitic nematodes cause serious diseases in humans, animals, and plants. They have limited lipid metabolism and are reliant on lipid-binding proteins to acquire these metabolites from their hosts. Several structurally novel families of lipidbinding proteins in nematodes have been described, including the fatty acid-and retinoid-binding protein family (FAR). In Caenorhabditis elegans, used as a model for studying parasitic nematodes, eight C. elegans FAR proteins have been described. The crystal structure of C. elegans FAR-7 is the first structure of a FAR protein, and it exhibits a novel fold. It differs radically from the mammalian fatty acid-binding proteins and has two ligand binding pockets joined by a surface groove. The first can accommodate the aliphatic chain of fatty acids, whereas the second can accommodate the bulkier retinoids. In addition to demonstrating lipid binding by fluorescence spectroscopy, we present evidence that retinol binding is positively regulated by casein kinase II phosphorylation at a conserved site near the bottom of the second pocket. far-7::GFP (green fluorescent protein) expression shows that it is localized in the head hypodermal syncytia and the excretory cell but that this localization changes under starvation conditions. In conclusion, our study provides the basic structural and functional information for investigation of inhibitors of lipid binding by FAR proteins.Hydrophobic lipophilic molecules such as fatty acids, eicosanoids, retinoids, and steroids have important functions both as energy sources and in metabolic signaling. They affect fundamental cellular processes such as gene transcription, cell development, inflammation, and immune response (1-3). The cellular cytosol is hydrophilic, and lipids need to be solubilized and protected from chemical damage. Their transport and availability are tightly regulated. Proteins that coordinate the lipid traffic include lipoproteins (such as the low density lipoprotein) and carrier proteins, known as lipid-binding proteins (LBPs).2 In vertebrates LBPs belong to the ␤-sheet calycin superfamily (lipocalins and fatty acid-binding proteins (FABPs)) or the ␣-helical serum albumin-like superfamily. Nematodes are one of the most abundant groups of multicellular organisms. Parasitic nematodes cause serious and difficult to treat diseases in humans, animals, and plants affecting human health as well as having a negative impact on agricultural economics. It is estimated that more than one-sixth of the earth's population (mainly in developing countries), suffers from nematode infections, and at least 4 of the 15 neglected tropical diseases listed by the World Health Organization are caused by nematodes. Parasitic worms possess limited lipid metabolism and depend on import of essential lipids from their host (4), which makes the lipid transporters good targets for chemoprophylactic treatments. A 14-kDa FABP (Sm14) has been proposed as a vaccine candidate against Schistosoma mansoni in humans and Fasciola hepatica in cattle and sheep (5, ...

Glutathione (GSH) and GSH-dependent enzymes play a key role in cellular detoxification processes that enable organism to cope with various internal and environmental stressors. However, it is often not clear, which components of the complex GSH-metabolism are required for tolerance towards a certain stressor. To address this question, a small scale RNAi-screen was carried out in Caenorhabditis elegans where GSH-related genes were systematically knocked down and worms were subsequently analysed for their survival rate under sub-lethal concentrations of arsenite and the redox cycler juglone. While the knockdown of γ-glutamylcysteine synthetase led to a diminished survival rate under arsenite stress conditions, GSR-1 (glutathione reductase) was shown to be essential for survival under juglone stress conditions. gsr-1 is the sole GSR encoding gene found in C. elegans. Knockdown of GSR-1 hardly affected total glutathione levels nor reduced glutathione/glutathione disulphide (GSH/GSSG) ratio under normal laboratory conditions. Nevertheless, when GSSG recycling was impaired by gsr-1(RNAi), GSH synthesis was induced, but not vice versa. Moreover, the impact of GSSG recycling was potentiated under oxidative stress conditions, explaining the enormous effect gsr-1(RNAi) knockdown had on juglone tolerance. Accordingly, overexpression of GSR-1 was capable of increasing stress tolerance. Furthermore, expression levels of SKN-1-regulated GSR-1 also affected life span of C. elegans, emphasising the crucial role the GSH redox state plays in both processes.

Background:The novel ubiquitin-like modifier (UBL) Ufm1 has essential functions in mammalian embryonic development. Results: The Ufm1 cascade in Caenorhabditis elegans is required for normal growth and development and is involved in cellular stress response. Conclusions: The C. elegans Ufm1 cascade is an antagonist of the unfolded protein response. Significance: The C. elegans Ufm1 cascade offers a unique opportunity to understand the fundamentals underlining this UBL.

Interactions of cells with supramolecular aggregates of the extracellular Matrix (ECM) are mediated, in part, by cell surface receptors of the integrin family. These are important molecular components of cell surfacesuprastructures regulating cellular activities in general. A subfamily of β1-integrins with von Willebrand-factor A-like domains (I-domains) in their α-chains can bind to collagen molecules and, therefore, are considered as important cellular mechano-receptors. Here we show that chondrocytes strongly bind to cartilage collagens in the form of individual triple helical molecules but very weakly to fibrils formed by the same molecules.We also find that chondrocyte integrins α1β1-, α2 β1-and α10β1-integrins and their I-domains have the same characteristics. Nevertheless we find integrin binding to mechanically generated cartilage fibril fragments, which also comprise peripheral non-collagenous material. We conclude that cell adhesion results from binding of integrin-containing adhesion suprastructures to the non-collagenous fibril periphery but not to the collagenous fibril cores. The biological importance of the well-investigated recognition of collagen molecules by integrins is unknown. Possible scenarios may include fibrillogenesis, fibril degradation and/orphagocytosis, recruitment of cells to remodeling sites, or molecular signaling across cytoplasmic membranes. In these circumstances, collagen molecules may lack a fibrillar organization. However, other processes requiring robust biomechanical functions, such as fibril organization in tissues, cell division, adhesion, or migration, do not involve direct integrin-collagen interactions.

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Pyrimidines are important metabolites in all cells. Levels of cellular pyrimidines are controlled by multiple mechanisms, with one of these comprising the reductive degradation pathway. In the model invertebrate Caenorhabditis elegans, two of the three enzymes of reductive pyrimidine degradation have previously been characterized. The enzyme catalysing the final step of pyrimidine breakdown, 3‐ureidopropionase (β‐alanine synthase), had only been identified based on homology. We therefore cloned and functionally expressed the 3‐ureidopropionase of C. elegans as hexahistidine fusion protein. The purified recombinant enzyme readily converted the two pyrimidine degradation products: 3‐ureidopropionate and 2‐methyl‐3‐ureidopropionate. The enzyme showed a broad pH optimum between pH 7.0 and 8.0. Activity was highest at approximately 40 °C, although the half‐life of activity was only 65 s at that temperature. The enzyme showed clear Michaelis–Menten kinetics, with a Km of 147 ± 26 μm and a Vmax of 1.1 ± 0.1 U·mg protein−1. The quaternary structure of the recombinant enzyme was shown to correspond to a dodecamer by ‘blue native’ gel electrophoresis and gel filtration. The organ specific and subcellular localization of the enzyme was determined using a translational fusion to green fluorescent protein and high expression was observed in striated muscle cells. With the characterization of the 3‐ureidopropionase, the reductive pyrimidine degradation pathway in C. elegans has been functionally characterized. Structured digital abstract  http://mint.bio.uniroma2.it/mint/search/interaction.do?interactionAc=MINT-7986015: 3‐ureidopropionase (uniprotkb:http://www.uniprot.org/uniprot/Q19437) and 3‐ureidopropionase (uniprotkb:http://www.uniprot.org/uniprot/Q19437) bind (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0407) by blue native page (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0276)