Understanding the membrane dynamics of complex systems is essential to follow their function. As molecules in membranes can be in a rigid or mobile state depending on external (temperature, pressure) or internal (pH, domains, etc.) conditions, we have developed NMR methods to filter highly mobile molecular parts from others that are in more restricted environments. Cross Polarization (CP),...
Keywords: Bacteria, membrane, lipid profile, DMS-DA6-NH2, mechanism of action, Nuclear Magnetic Resonance
Abstract:
Staphylococcus aureus is a Gram-positive pathogenic bacterium that is resistant to a wide range of antibiotics. DMS-DA6-NH2 (DA6) is a novel antimicrobial peptide (AMP) that has high efficacy on various bacterial strains (1). In vivo 2H solid-state Nuclear Magnetic Resonance...
We developed an azide-modified lipid with the potential to be used in photocrosslinking studies in lipid bilayers [1,2] or monolayers[3] with interaction partners, such as peptides or proteins. The UV-activatable lipid is a phosphatidylcholine (PC) and bears a terminal azide moiety in one of its hydrophobic tails (AzidoPC). Here, we present systematic monolayer studies of pure AzidoPC and its...
Cell Penetrating Peptides (CPPs) are small peptides able to cross cell membranes in a receptor-independent way. They are generally cationic and often amphipathic, which leads them to interact favourably with membrane lipids and glycosaminoglycans (GAGs) of the cell surface. Their internalisation can occur according to two pathways: endocytosis which is energy-dependent and translocation which...
Lipid flippases (P4-ATPases) mediate active transport of phospholipids from the exoplasmic leaflet to the cytoplasmic one, in order to establish and maintain phospholipid asymmetry in eukaryotic membranes. This asymmetry is tightly regulated, and important for numerous cellular processes such as membrane trafficking, signaling, apoptosis, cytokinesis and cell fusion. The human genome encodes...
The overproduction of the b subunit of the FoF1-ATP synthase, AtpF, induces massive intracellular membrane (ICM) proliferation in C43(DE3) 1. We identified shorter AtpF variants that lead either to ICM accumulation or vesicle formation (AtpF 1_42 FlAsH). Partial deletions of the AtpF gene lead to intermediate phenotypes.
Here, we investigate the role of the dimerization of the overexpressed...
Poxviruses are enveloped, large cytoplasmic dsDNA viruses that have epidemic potential. Since its successful use as a live vaccine to eradicate Variola virus, the etiologic agent of smallpox, Vaccinia virus (VACV) has become a model for poxvirus research. Early stages of poxvirus assembly rely on a unique membrane acquisition mechanism that does not involve wrapping or budding at cellular...
Total Internal Reflection Fluorescence (TIRF) Microscopy is based on the generation of evanescent waves on the surface of a glass coverslips enabling imaging with a depth of focus of about 100-200 nm. This makes TIRF microscopy a key instrument to observe cell – substrates contact region and to provide a detailing understanding of membrane particles dynamics. These 2 last decades, TIRF...
Betaine lipids are non-phosphorus glycerolipids and can represent up to 40% of the membrane lipid content. There are three basic types of betain lipids: DGTS, DGTA and DGCC distributed in photosynthetic organisms such as ferns, mousses macro- and microalgae. In contrast, it is interesting to notice that there are no betaine lipids in seed plants (angiosperms and gymnosperms). Under phosphate...
Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular parasite. The ability of this parasite to infect host cells depends on its capacity to release unique factors from special organelles called rhoptries, micronemes, and dense granules. The biogenesis of these organelles relies on vesicular trafficking events whose molecular bases are poorly known. In...
Membrane bilayers in eukaryotic cells display an asymmetrical transbilayer lipid distribution, i.e. a different lipid concentration in their two leaflets, which is important for fundamental cellular processes like vesicle-mediated trafficking or recruitment of signaling proteins to the membrane. Transbilayer lipid asymmetry is maintained by specific membrane proteins, flippases and floppases,...
Membrane fusion plays an important role in several biological processes. Thus, it is essential to explore the mechanism of vesicle fusion. Fusion is frequently induced by SNARE proteins attached to the membrane. These highly complicated proteins can be modelled by coiled-coil complexes (CCs). Typically, CCs are constructed of heptad repeating hydrophobic and polar residues.
To indicate...
Toxin-antitoxin systems are genetic modules widely spread in bacterial genomes. They contain a toxin, which stops the bacteria’s growth and an antitoxin, which inhibits toxin’s expression. Under normal conditions, the antitoxin is produced concomitantly with the toxin, so the toxin is not translated. Under a stress, the antitoxin is not produced anymore, so the toxin can be translated, act on...
Here we investigate the lipid membrane reorganization caused by sorption of ethanol from the gas phase. The physical effects of the short chain alcohols, e.g. ethanol & butanol, on cell membranes seem to be a fundamental limitation on the amount of alcohol that can be produced by fermentation. This technology is already an important renewable alternative to fossil fuels. We hope that...
Ist2 is a yeast transmembrane protein localized in the endoplasmic reticulum (ER). It is a structural homolog of TMEM16 proteins, a family of transporters described as scramblases, i.e., proteins that catalyze facilitated diffusion of lipids in a non-specific manner, and/or anion channels.
Ist2 is made of a N-terminal transmembrane domain, as well as a long cytosolic C-terminus that binds to...
Vascular endothelial-cadherin (VE-cadherin) is the most important transmembrane component of endothelial adherens junctions. A cytokine-induced phosphorylation of VE-cadherin cytoplasmic domain was reported to trigger cleavage of its extracellular domain, producing the soluble form of the protein – soluble vascular endothelial-cadherin (sVE) [1]. Hence, the presence of sVE in human serum and...
In the context of pharmacology, drug membrane transporters play a central role in local pharmacokinetics, i.e., the intracellular drug concentrations of tissues of interest. Particular attention should be paid to membrane transporters located in liver and kidneys given their importance in drug metabolism and elimination. This is particularly true for multidrug-resistance associated proteins...
In the frameworks of personalized medicine, deciphering the sources of variability in patient drug responses requires the understanding of underlying processes modulating drug pharmacokinetics (PK). This is particularly true to bridge the gap between systemic and local PK, i.e., drug concentration close to its target. In this context,
drugs membrane transporters play a central role...
Amyloid β42 (Aβ42) is predominantly found in the form of plaques in the brain tissues of Alzheimer's disease and is mainly responsible for cognitive dysfunctionality in Alzheimer’s. Aβ depending upon aggregation states Aβ42-monomer (M)/β-sheets/oligomer (O)/fibril (F), and amino acid length affects the model membrane mimetic systems [1-4]. The plasma membrane is the first biological structure...
Among the many assemblies that lipid molecules are able to form, lipid nanotubes (LNTs) are currently one of the most interesting structures in the framework of nanomaterials fundamentals and design. Their high-aspect ratio, tunable diameter size and biocompatibility, enables them for a plethora of biotechnological applications such as drug delivery, protein separation and DNA detection.1,2...
For a long time NOX enzymes have been thought to be a landmark of pluricellular organisms where the production of reactive oxygen species could be associated to physiological function related to the multicellularity (immune defense, vascular tone regulation, hormone synthesis, etc..).
However, our group identified in 2017, a first ancestor to eukaryotic NOX in bacteria with the...
Mitochondria are crucial for energy metabolism. In living cells, they undergo continuous shape transformations in order to perform various biological functions such as fission and fusion rearrangement. The shape of the membrane is determined by the bulk mechanical parameters of the membrane such as lateral tension, bending modulus and spontaneous curvature. These parameters, in turns, depend...
To study the dynamics and function of cellular membranes it is important to understand their structure. This involves experiments on model systems and can profit from a probe that is able to access different scales of size and time: thermal neutrons. Since the pioneering work in the seventies on cell membrane structure by neutron scattering, developments driven by constantly improving neutron...
It has been suggested that the intramembrane rhomboid protease GlpG can thin membranes, possibly explaining the observation that rhomboids diffuse faster than the high viscosity of the lipid membrane would allow. Molecular dynamics simulations have shown membrane thinning by GlpG in both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) membranes. To experimentally test the membrane...
