“…Such selective incorporation could be driven by direct lipid binding by capsid proteins, enrichment of certain lipid species at sites of viral budding, or physical properties of the viral envelope that cause partitioning of lipids into or out of the nascent envelope during viral budding. Because GDGT-0 is more flexible than the cyclopentane-containing GDGT lipids (Schwarzmann et al, 2015), it can better adopt the horseshoe conformations that have a lower free energy in the highly curved AFV-1 envelope (Galimzyanov et al, 2016). We therefore hypothesize that selective partitioning of GDGT lipids due to the curvature of the envelope is the mechanism for GDGT-0 enrichment in the AFV-1 membrane.10.7554/eLife.26268.010Figure 6.Lipid distribution of virions different from host cells.( a ) Chemical diagrams for the lipids found in Acidianus hospitalis and AFV1.…”
Biological membranes create compartments, and are usually formed by lipid bilayers. However, in hyperthermophilic archaea that live optimally at temperatures above 80°C the membranes are monolayers which resemble fused bilayers. Many double-stranded DNA viruses which parasitize such hosts, including the filamentous virus AFV1 of Acidianus hospitalis, are enveloped with a lipid-containing membrane. Using cryo-EM, we show that the membrane in AFV1 is a ~2 nm-thick monolayer, approximately half the expected membrane thickness, formed by host membrane-derived lipids which adopt a U-shaped ‘horseshoe’ conformation. We hypothesize that this unusual viral envelope structure results from the extreme curvature of the viral capsid, as ‘horseshoe’ lipid conformations favor such curvature and host membrane lipids that permit horseshoe conformations are selectively recruited into the viral envelope. The unusual envelope found in AFV1 also has many implications for biotechnology, since this membrane can survive the most aggressive conditions involving extremes of temperature and pH.DOI:
http://dx.doi.org/10.7554/eLife.26268.001
“…Such selective incorporation could be driven by direct lipid binding by capsid proteins, enrichment of certain lipid species at sites of viral budding, or physical properties of the viral envelope that cause partitioning of lipids into or out of the nascent envelope during viral budding. Because GDGT-0 is more flexible than the cyclopentane-containing GDGT lipids (Schwarzmann et al, 2015), it can better adopt the horseshoe conformations that have a lower free energy in the highly curved AFV-1 envelope (Galimzyanov et al, 2016). We therefore hypothesize that selective partitioning of GDGT lipids due to the curvature of the envelope is the mechanism for GDGT-0 enrichment in the AFV-1 membrane.10.7554/eLife.26268.010Figure 6.Lipid distribution of virions different from host cells.( a ) Chemical diagrams for the lipids found in Acidianus hospitalis and AFV1.…”
Biological membranes create compartments, and are usually formed by lipid bilayers. However, in hyperthermophilic archaea that live optimally at temperatures above 80°C the membranes are monolayers which resemble fused bilayers. Many double-stranded DNA viruses which parasitize such hosts, including the filamentous virus AFV1 of Acidianus hospitalis, are enveloped with a lipid-containing membrane. Using cryo-EM, we show that the membrane in AFV1 is a ~2 nm-thick monolayer, approximately half the expected membrane thickness, formed by host membrane-derived lipids which adopt a U-shaped ‘horseshoe’ conformation. We hypothesize that this unusual viral envelope structure results from the extreme curvature of the viral capsid, as ‘horseshoe’ lipid conformations favor such curvature and host membrane lipids that permit horseshoe conformations are selectively recruited into the viral envelope. The unusual envelope found in AFV1 also has many implications for biotechnology, since this membrane can survive the most aggressive conditions involving extremes of temperature and pH.DOI:
http://dx.doi.org/10.7554/eLife.26268.001
“…Small endo‐lysosomal vesicles characterized by a high content of bis(monoacylglycero)phosphate, with the sphingolipids in the outer layer facing the lysosol with a topology more suitable to the enzymatic hydrolysis, are rapidly formed in the late lysosomes (Schwarzmann et al . ). Thus, both lysosomal membrane sphingolipids and endo‐lysosomal vesicle membrane sphingolipids can be found in the lysosomes.…”
Ceramide, sphingomyelin, and glycosphingolipids (both neutral and acidic) are characterized by the presence in the lipid moiety of an aliphatic base known as sphingosine. Altogether, they are called sphingolipids and are particularly abundant in neuronal plasma membranes, where, via interactions with the other membrane lipids and membrane proteins, they play a specific role in modulating the cell signaling processes. The metabolic pathways determining the plasma membrane sphingolipid composition are thus the key point for functional changes of the cell properties. Unnatural changes of the neuronal properties are observed in sphingolipidoses, lysosomal storage diseases occurring when a lysosomal sphingolipid hydrolase is not working, leading to the accumulation of the substrate and to its distribution to all the cell membranes interacting with lysosomes. Moreover, secondary accumulation of sphingolipids is a common trait of other lysosomal storage diseases. Keywords: gangliosides, lysosome, membrane fusion, sphingolipidoses, sphingolipids, sphingomyelin.This article is part of the Special Issue "Lysosomal Storage Disorders".Sphingolipids are amphiphilic membrane lipids characterized by the presence of sphingosine, an amino-and-hydroxy alkylic long chain. After more than a century of studies, we now know their structure, their physico-chemical properties, their distribution and content in cells and tissues of many animal species, including humans . The final cellular site for sphingolipids is the plasma membrane, however, their complex metabolic pathway requires many intracellular processes, so that a not negligible portion of them is also found intracellularly (Sandhoff and Kolter 2003;Schulze et al. 2009;Kolter and Sandhoff 2010;Hannun and Obeid 2018). As amphiphilic compounds they contain a hydrophilic head group, for example a saccharide, an oligosaccharide, a phosphocholine, protruding into the cell aqueous environment, and a hydrophobic chain called ceramide, in which the sphingosine is linked with a fatty acid via an amidic bond, inserted into the outer layer of plasma membrane.Sphingolipids are typically asymmetric components of the plasma membranes enriched in the outer leaflet (van Meer and Hoetzl 2010;van Meer 2011;Fujimoto and Parmryd 2016), however, it cannot be excluded that a minor pool of them could be transiently inserted into the inner layer with the hydrophilic group facing the cytosol. The hydrophilic group, thanks to the presence of carbohydrates and/or ionic charges, attracts water and ions, forms hydrogen bonds and easily interacts with the group of membrane components protruding from the membrane itself. At the water-lipid interface, the sphingolipid ceramide amide linkage accepts hydrogen bonds on the carbonyl group and donates hydrogen bonds via the N-H group, allowing the formation of a double linkage, which works as a padlock within molecules (Fig. 1). The lipid moiety inserted into the lipid layer interacts with the lipid portion of the cholesterol in the membrane and with dip...
“…Using this enzyme assay the addition of the SapDs S1 – S3 gave increased degradation of ceramide, albeit with little difference between each glycoform (Scheme b). In contrast, the membrane assay systems developed for measuring binding of saposins to immobilized liposomes by SPR and the fusion of specifically labeled liposomes showed carbohydrate‐dependent activities for SapD (Scheme c,d). SapD S1 (smallest glycan) showed the strongest binding to liposomes and also the highest liposome fusion activity.…”
The main glycoforms of the hydrophobic lysosomal glycoprotein saposin D( SapD) were synthesized by native chemical ligation. An approach for the challenging solid-phase synthesis of the fragments was developed. Three SapD glycoforms were obtained following ag eneral and robust refolding and purification protocol. Acrystal structure of one glycoform confirmed its native structure and disulfide pattern. Functional assays revealed that the lipid-binding properties of three SapD glycoforms are highly affected by the single sugar moiety of SapD showing ad ependency of the size and the type of Nglycan.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.
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