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Membrane curvature

Tamako Nishimura, Nobuhiro Morone, Shiro Suetsugu
Lipid membranes are structural components of cell surfaces and intracellular organelles. Alterations in lipid membrane shape are accompanied by numerous cellular functions, including endocytosis, intracellular transport, and cell migration. Proteins containing Bin-Amphiphysin-Rvs (BAR) domains (BAR proteins) are unique, because their structures correspond to the membrane curvature, that is, the shape of the lipid membrane. BAR proteins present at high concentration determine the shape of the membrane, because BAR domain oligomers function as scaffolds that mould the membrane...
March 14, 2018: Biochemical Society Transactions
Yi Yu, Su Chen, Xiaoqiang Mo, Jihong Gong, Chenhong Li, Xiaofei Yang
Complexins, binding to assembling soluble NSF-attachment protein receptor (SNARE) complexes, activate Ca2+ triggered exocytosis and clamp spontaneous release in the presynaptic terminal. Functions of complexin are structural dependent and mechanistically distinct. To further understand the functional/structural dependence of complexin, here we show that the accessory and central α-helices of complexin are sufficient in activation of Ca2+ triggered vesicle fusion but not in clamping spontaneous release. Targeting the two α-helices to synaptic vesicle suppresses spontaneous release, thus further emphasizing the importance of curvature membrane localization in clamping function...
2018: Frontiers in Molecular Neuroscience
Vineet Choudhary, Gonen Golani, Amit S Joshi, Stéphanie Cottier, Roger Schneiter, William A Prinz, Michael M Kozlov
Lipid droplets (LDs) store fats and play critical roles in lipid and energy homeostasis. They form between the leaflets of the endoplasmic reticulum (ER) membrane and consist of a neutral lipid core wrapped in a phospholipid monolayer with proteins. Two types of ER-LD architecture are thought to exist and be essential for LD functioning. Maturing LDs either emerge from the ER into the cytoplasm, remaining attached to the ER by a narrow membrane neck, or stay embedded in the ER and are surrounded by ER membrane...
March 3, 2018: Current Biology: CB
Svetlana S Efimova, Evgeny G Chulkov, Olga S Ostroumova
The effects of local anesthetics (LAs), namely, lidocaine (LDC), prilocaine (PLC), mepivacaine (MPV), bupivacaine (BPV), procaine (PC), and tetracaine (TTC), on the steady-state transmembrane conductance induced by the cis-side addition of the antifungal polyene macrolide antibiotic, nystatin (NYS), in planar lipid bilayers were studied. The addition of TTC to model membranes comprising DOPC and cholesterol (33 mol%) led to a nearly twenty-fold increase in the steady-state NYS-induced membrane conductance...
March 8, 2018: Colloids and Surfaces. B, Biointerfaces
Zhen Li, Yonghui Zhang, Chun Chan, Chunyi Zhi, Xiaolin Cheng, Jun Fan
Two-dimensional (2D) materials can mechanically insert into cell membranes and extract lipids out, thus leading to the destruction of cell integrity. On the one hand, the cytotoxicity of 2D materials can be harnessed in surface engineering to resist biofouling; on the other hand, it causes great concern on in vivo biomedical applications ranging from drug delivery to nano-imaging. To understand the nature of this cytotoxic behavior and find strategies to control it, we performed molecular dynamics (MD) simulations on the lipid extraction of hexagonal boron nitride (BN) nanosheets from lipid membranes...
March 8, 2018: ACS Nano
Naohito Urakami, Takehiro Jimbo, Yuka Sakuma, Masayuki Imai
We investigated the effects of lipid geometry on vesicle division using coarse grained molecular dynamics simulations. When the vesicle is composed of zero and negative spontaneous curvature lipids (ZSLs and NSLs), the difference in their molecular spontaneous curvatures destabilizes the neck of the limiting shape vesicle. In the vesicle division pathway, the neck developed into the stalk intermediates. The stalk was broken when the NSLs were expelled from the stalk. Free energy analysis shows that the coupling between the lipid geometry and the Gaussian rigidity is responsible for the observed vesicle division...
March 8, 2018: Soft Matter
Richard J Alsop, Sebastian Himbert, Alexander Dhaliwal, Karin Schmalzl, Maikel C Rheinstädter
Local structure and dynamics of lipid membranes play an important role in membrane function. The diffusion of small molecules, the curvature of lipids around a protein and the existence of cholesterol-rich lipid domains (rafts) are examples for the membrane to serve as a functional interface. The collective fluctuations of lipid tails, in particular, are relevant for diffusion of membrane constituents and small molecules in and across membranes, and for structure and formation of membrane domains. We studied the effect of aspirin (acetylsalicylic acid, ASA) on local structure and dynamics of membranes composed of dimyristoylphosphocholine (DMPC) and cholesterol...
February 2018: Royal Society Open Science
Morgan Chabanon, Padmini Rangamani
Formation of membrane necks is crucial for fission and fusion in lipid bilayers. In this work, we seek to answer the following fundamental question: what is the relationship between protein-induced spontaneous mean curvature and the Gaussian curvature at a membrane neck? Using an augmented Helfrich model for lipid bilayers to include membrane-protein interaction, we solve the shape equation on catenoids to find the field of spontaneous curvature that satisfies mechanical equilibrium of membrane necks. In this case, the shape equation reduces to a variable coefficient Helmholtz equation for spontaneous curvature, where the source term is proportional to the Gaussian curvature...
March 7, 2018: Soft Matter
Diego Masone, Marina Uhart, Diego Bustos
Curvature-related processes are of major importance during protein-membrane interactions. The illusive simplicity of membrane reshaping masks a complex molecular process crucial for a wide range of biological functions like fusion, endo and exocytosis, cell division, cytokinesis and autophagy. To date, no functional expression of a reaction coordinate capable of biasing molecular dynamics simulations to produce membrane curvature has been reported. This represents a major drawback given that the adequate identification of proper collective variables to enhance sampling is fundamental for restrained dynamics techniques...
March 5, 2018: Journal of Chemical Theory and Computation
Ludger Johannes, Weria Pezeshkian, John H Ipsen, Julian C Shillcock
Clustering of extracellular ligands and proteins on the plasma membrane is required to perform specific cellular functions, such as signaling and endocytosis. Attractive forces that originate in perturbations of the membrane's physical properties contribute to this clustering, in addition to direct protein-protein interactions. However, these membrane-mediated forces have not all been equally considered, despite their importance. In this review, we describe how line tension, lipid depletion, and membrane curvature contribute to membrane-mediated clustering...
March 1, 2018: Trends in Cell Biology
Miglena I Angelova, Anne-Florence Bitbol, Michel Seigneuret, Galya Staneva, Atsuji Kodama, Yuka Sakuma, Toshihiro Kawakatsu, Masayuki Imai, Nicolas Puff
Most biological molecules contain acido-basic groups that modulate their structure and interactions. A consequence is that pH gradients, local heterogeneities and dynamic variations are used by cells and organisms to drive or regulate specific biological functions including energetic metabolism, vesicular traffic, migration and spatial patterning of tissues in development. While the direct or regulatory role of pH in protein function is well documented, the role of hydrogen and hydroxyl ions in modulating the properties of lipid assemblies such as bilayer membranes is only beginning to be understood...
March 3, 2018: Biochimica et Biophysica Acta
Shu Y Liao, Myungwoon Lee, Mei Hong
Many membrane proteins sense and induce membrane curvature for function, but structural information about how proteins modulate their structures to cause membrane curvature is sparse. We review our recent solid-state NMR studies of two virus membrane proteins whose conformational equilibrium is tightly coupled to membrane curvature. The influenza M2 proton channel has a drug-binding site in the transmembrane (TM) pore. Previous chemical shift data indicated that this pore-binding site is lost in an M2 construct that contains the TM domain and a curvature-inducing amphipathic helix...
February 28, 2018: Journal of Structural Biology
Jonathan R Burns, Stefan Howorka
DNA nanopores are a recent class of bilayer-puncturing nanodevices that can help advance biosensing, synthetic biology, and nanofluidics. Here, we create archetypal lipid-anchored DNA nanopores and characterize them with a nanoprobe-based approach to gain essential information about their interactions with bilayers. The strategy determines the molecular accessibility of DNA pores with a nuclease and can thus distinguish between the nanopores' membrane-adhering and membrane-spanning states. The analysis reveals, for example, that pores interact with bilayers in two steps whereby fast initial membrane tethering is followed by slower reorientation to the puncturing state...
March 1, 2018: ACS Nano
Thomas R Weikl
Besides direct protein-protein interactions, indirect interactions mediated by membranes play an important role for the assembly and cooperative function of proteins in membrane shaping and adhesion. The intricate shapes of biological membranes are generated by proteins that locally induce membrane curvature. Indirect curvature-mediated interactions between these proteins arise because the proteins jointly affect the bending energy of the membranes. These curvature-mediated interactions are attractive for crescent-shaped proteins and are a driving force in the assembly of the proteins during membrane tubulation...
February 28, 2018: Annual Review of Physical Chemistry
Leeladhar, Parul Raturi, J P Singh
Photomechanical actuation is the conversion of light energy into mechanical energy through some smart materials. Infrared-responsive smart materials have become an emerging field of research due to easy availability and eco-friendly nature of their stimulus in the form of sunlight, which contains about 50% of near-infrared(nIR) making these materials useful at macro-scale photoactuator applications. Here, we demonstrate fabrication of highly versatile nIR triggered photoactuators based on graphene oxide/polycarbonate bilayers that offers fast, low-cost fabrication, large deflection, reversible actuation and wavelength-selective response...
February 27, 2018: Scientific Reports
Henri G Franquelim, Alena Khmelinskaia, Jean-Philippe Sobczak, Hendrik Dietz, Petra Schwille
Membrane sculpting and transformation is essential for many cellular functions, thus being largely regulated by self-assembling and self-organizing protein coats. Their functionality is often encoded by particular spatial structures. Prominent examples are BAR domain proteins, the 'banana-like' shapes of which are thought to aid scaffolding and membrane tubulation. To elucidate whether 3D structure can be uncoupled from other functional features of complex scaffolding proteins, we hereby develop curved DNA origami in various shapes and stacking features, following the presumable design features of BAR proteins, and characterize their ability for membrane binding and transformation...
February 23, 2018: Nature Communications
Emma K Eriksson, Víctor Agmo Hernández, Katarina Edwards
Ubiquinone-10 (Q10) plays a pivotal role as electron-carrier in the mitochondrial respiratory chain, and is also well known for its powerful antioxidant properties. Recent findings suggest moreover that Q10 could have an important membrane stabilizing function. In line with this, we showed in a previous study that Q10 decreases the permeability to carboxyfluorescein (CF) and increases the mechanical strength of 1-palmitoyl-2-oleyl-sn-glycero-phosphocholine (POPC) membranes. In the current study we report on the effects exerted by Q10 in membranes having a more complex lipid composition designed to mimic that of the inner mitochondrial membrane (IMM)...
February 19, 2018: Biochimica et Biophysica Acta
Saman Hussain, Carl N Wivagg, Piotr Szwedziak, Felix Wong, Kaitlin Schaefer, Thierry Izoré, Lars D Renner, Matthew J Holmes, Yingjie Sun, Alexandre W Bisson-Filho, Suzanne Walker, Ariel Amir, Jan Löwe, Ethan C Garner
MreB is essential for rod shape in many bacteria. Membrane-associated MreB filaments move around the rod circumference, helping to insert cell wall in the radial direction to reinforce rod shape. To understand how oriented MreB motion arises, we altered the shape of Bacillus subtilis . MreB motion is isotropic in round cells, and orientation is restored when rod shape is externally imposed. Stationary filaments orient within protoplasts, and purified MreB tubulates liposomes in vitro , orienting within tubes...
February 22, 2018: ELife
Reinhard Lipowsky
Aqueous two-phase systems and water-in-water emulsions have attracted much recent interest. Here, we theoretically study the interactions of such systems with biomimetic membranes and giant unilamellar vesicles (GUVs). For partial wetting, the water-water interface and the membrane form a three-phase contact line that partitions the membrane into two distinct segments with different tensions and different curvature-elastic properties. On the nanometer scale, the capillary forces arising from the water-water interface lead to a smoothly curved membrane that forms an intrinsic contact angle with the interface...
February 21, 2018: Journal of Physical Chemistry. B
Joana S Sousa, Edoardo D'Imprima, Janet Vonck
Mitochondria are the power stations of the eukaryotic cell, using the energy released by the oxidation of glucose and other sugars to produce ATP. Electrons are transferred from NADH, produced in the citric acid cycle in the mitochondrial matrix, to oxygen by a series of large protein complexes in the inner mitochondrial membrane, which create a transmembrane electrochemical gradient by pumping protons across the membrane. The flow of protons back into the matrix via a proton channel in the ATP synthase leads to conformational changes in the nucleotide binding pockets and the formation of ATP...
2018: Sub-cellular Biochemistry
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