Membrane structure and assembly

  • Article
    | Open Access

    Circularised nanodiscs (cNDs) are able to stabilise large lipid bilayer patches and are used for structural and functional studies. Current techniques to build cNDs have numerous steps and low yields; here the authors report a single step construction method using the SpyCatcher-SpyTag system.

    • Shanwen Zhang
    • , Qian Ren
    •  & Huan Bao
  • Article
    | Open Access

    A variety of artificial cells springs from the functionalization of liposomes with proteins but these models suffer from low durability without repair and replenishment mechanisms. Here, the authors show that synthetic amphiphile membranes undergo SNARE-mediated fusion, and determine bending rigidity and pore edge tension as key parameters for fusion.

    • Lado Otrin
    • , Agata Witkowska
    •  & Tanja Vidaković-Koch
  • Article
    | Open Access

    The folding of outer membrane proteins (OMPs) is catalyzed by the βbarrel assembly machinery (BAM). Here, structural and functional analyses of BAM stabilized in distinct conformations elucidate the roles of lateral gate opening and interactions of BAM with the lipid bilayer in OMP assembly.

    • Paul White
    • , Samuel F. Haysom
    •  & Sheena E. Radford
  • Article
    | Open Access

    Gangliosides such as GM1 present in the outer leaflet of the plasma membrane of eukaryotic cells are essential for many cellular functions and pathogenic interactions. Here the authors show that the acyl chain structure of GM1 determines the establishment of nanodomains when actively clustered by actin, which depended on membrane cholesterol and phosphatidylserine or superimposed by the GM1-binding bacterial cholera toxin.

    • Senthil Arumugam
    • , Stefanie Schmieder
    •  & Ludger Johannes
  • Article
    | Open Access

    Proteins need to overcome energy barriers to induce intermediate steps in membrane fusion. Using lipid vesicles in which progression to hemifusion is arrested, the authors show that the metastable intermediate is enhanced by divalent cations and is characterized by the absence of proteins and local membrane thickening. Simulations reveal that thickening is induced by dehydration of the membrane surface.

    • Agata Witkowska
    • , Leonard P. Heinz
    •  & Reinhard Jahn
  • Article
    | Open Access

    Cyanobacterial thylakoid membranes host the molecular machinery for the light-dependent reactions of photosynthesis and respiratory electron flow. Here, the authors show that newly synthesized thylakoids emerge between the plasma membrane and pre-existing thylakoids and describe the time-dependent assembly process of photosynthetic complexes.

    • Tuomas Huokko
    • , Tao Ni
    •  & Lu-Ning Liu
  • Article
    | Open Access

    Cytoskeletal networks support and direct cell shape and guide intercellular transport, but relatively little is understood about the self-organization of cytoskeletal components on the scale of an entire cell. Here, authors use an in vitro system and observe the assembly of different types of actin networks and the condensation of membrane-bound actin into single rings.

    • Thomas Litschel
    • , Charlotte F. Kelley
    •  & Petra Schwille
  • Article
    | Open Access

    The cytoplasm in mammalian cells is considered homogeneous. Here authors report that the cytoplasmic fluidity is regulated in the blebbing cells, which is regulated by calcium concentration in the expanding blebs and involves the STIM-Orai1 pathway.

    • Kana Aoki
    • , Shota Harada
    •  & Junichi Ikenouchi
  • Article
    | Open Access

    The local lipid environment is known to affect the structure, stability and intercellular channel activity of gap junctions, however, the molecular basis for these effects remains unknown. Here authors report the CryoEM structure of Cx46/50 lipid-embedded channels, by which they reveal a lipid-induced stabilization to the channel.

    • Jonathan A. Flores
    • , Bassam G. Haddad
    •  & Steve L. Reichow
  • Article
    | Open Access

    The vacuolar-type H+ -ATPases (V-ATPase) hydrolyze ATP to pump protons across the plasma or intracellular membrane. Here authors report two cryo-EM structures of the intact V-ATPase from bovine brain with all the subunits including the subunit H, which is essential for ATPase activity.

    • Rong Wang
    • , Tao Long
    •  & Xiaochun Li
  • Article
    | Open Access

    While membrane contact sites between intracellular organelles are abundant, little is known about the contacts between membranes that delimit extracellular junctions within cells, such as intracellular parasites. Here authors demonstrate the segregation of a lipid transporter from a solute transporter in the malarial host-parasite interface.

    • Matthias Garten
    • , Josh R. Beck
    •  & Joshua Zimmerberg
  • Article
    | Open Access

    Formation of amyloid-beta (Aβ) oligomer pores in the membrane of neurons has been proposed to explain neurotoxicity in Alzheimer´s disease. Here authors present the 3D- structure of an Aβ oligomer formed in a membrane mimicking environment and observe that Aβ tetramers and octamers inserted into lipid bilayers as well-defined pores.

    • Sonia Ciudad
    • , Eduard Puig
    •  & Natàlia Carulla
  • Article
    | Open Access

    ESCRT-III complexes assemble in vivo inside membrane structures with a negative Gaussian curvature, but how membrane shape influences ESCRT-III polymerization remains unclear. Here authors use structural and biophysical methods to show how human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation.

    • Aurélie Bertin
    • , Nicola de Franceschi
    •  & Patricia Bassereau
  • Article
    | Open Access

    Assembling synthetic plant cell is difficult due to the presence of primary cell wall. Here, the authors describe the assembly of lipid-containing bodies that can be coated with cellulose and pectin, and show how these so-called plantosomes can be manipulated by changing surrounding milieu.

    • T. Paulraj
    • , S. Wennmalm
    •  & A. J. Svagan
  • Article
    | Open Access

    Cells maintain membrane fluidity by regulating lipid saturation, but the molecular mechanisms of this homeoviscous adaptation remain poorly understood. Here authors reconstituted the core machinery for regulating lipid saturation in baker’s yeast to directly characterize its response to defined membrane environments and uncover its mode-of-action.

    • Stephanie Ballweg
    • , Erdinc Sezgin
    •  & Robert Ernst
  • Article
    | Open Access

    Annexins are cytoplasmic proteins, which bind to membranes exposing negatively charged phospholipids in a Ca2+-dependent manner. Here the authors use high-speed atomic force microscopy and other techniques to show that annexin-V self-assembles into highly structured lattices that lead to a membrane phase transition on PS-rich membranes.

    • Yi-Chih Lin
    • , Christophe Chipot
    •  & Simon Scheuring
  • Article
    | Open Access

    The Bin/Amphiphysin/Rvs167 (BAR) domain superfamily, which includes FCH-BAR (F-BAR) domain proteins are membrane-sculpting proteins. Here the authors combine a range of techniques and show that the F-BAR domain of growth-arrest specific protein 7 (GAS7) forms two-dimensional sheets on flat membranes and that these oligomeric assemblies of GAS7 are required for the formation of phagocytic cups in macrophages.

    • Kyoko Hanawa-Suetsugu
    • , Yuzuru Itoh
    •  & Shiro Suetsugu
  • Article
    | Open Access

    Ultrathin membranes have demonstrated great promise for water purification technologies owing to their high permeance. Here the authors fabricate sub-10 nm, defect-free, robust membranes for dye remediation from water through the coordination-driven assembly of metal-organophosphates.

    • Xinda You
    • , Hong Wu
    •  & Zhongyi Jiang
  • Article
    | Open Access

    The dynamics of biomolecules can occur over a wide range of time and length scales. Here the authors develop a high-speed AFM height spectroscopy method to directly detect the motion of unlabeled molecules at Angstrom spatial and microsecond temporal resolution.

    • George R. Heath
    •  & Simon Scheuring
  • Article
    | Open Access

    Assembly of higher-order artificial vesicles can unlock new applications. Here, the authors use optical tweezers to construct user-defined 2D and 3D architectures of chemically distinct vesicles and demonstrate inter-vesicle communication and light-enabled compartment merging.

    • Guido Bolognesi
    • , Mark S. Friddin
    •  & Yuval Elani
  • Article
    | Open Access

    Outer membrane proteins (OMPs) in Gram-negative bacteria have restricted lateral mobility. Here, Rassam et al. show that the bacteriocin ColE9, via its interactions with OMPs, imposes this restricted mobility on the inner membrane proteins of the Tol-Pal complex.

    • Patrice Rassam
    • , Kathleen R. Long
    •  & Colin Kleanthous
  • Article
    | Open Access

    T cell activation is critically controlled by T cell receptor (TCR) signalling. Here the authors show, using live cell imaging, atomic force microscopy and modelling simulation, a prompt separation of TCR and CD45 that negatively correlates with TCR activation, supporting a refined kinetic segregation model of TCR signalling.

    • Yair Razvag
    • , Yair Neve-Oz
    •  & Eilon Sherman
  • Article
    | Open Access

    The Alzheimer protein Tau interacts with biological membranes, but the role of these interactions in regulating Tau function in health and disease remains unexplored. Here, the authors report on the discovery and characterization of neurotoxic oligomeric protein/phospholipid complexes.

    • Nadine Ait-Bouziad
    • , Guohua Lv
    •  & Hilal A. Lashuel
  • Article
    | Open Access

    Lipid rafts are plasma membrane domains that specifically recruit particular proteins. Here, the authors show that the surface area, length and palmitoylation of single-pass transmembrane domains are crucial for raft partitioning and propose a general model to predict protein association with rafts.

    • Joseph H. Lorent
    • , Blanca Diaz-Rohrer
    •  & Ilya Levental
  • Article
    | Open Access

    Lipopolysaccharides (LPS) are synthesized at the periplasmic side of the inner membrane of Gram-negative bacteria and are then extracted by the LptB2FG complex during the first step of LPS transport to the outer membrane. Here the authors present the LptB2FG structure, which supports an alternating lateral access mechanism for LPS extraction.

    • Haohao Dong
    • , Zhengyu Zhang
    •  & Changjiang Dong
  • Article
    | Open Access

    Membrane protein diffusion is affected by distinct mechanisms such as molecular crowding and medium elasticity. Here the authors present an analytical approach to analyse single particle trajectories and distinguish mixed subdiffusive processes affecting membrane protein mobility in living cells.

    • Yonatan Golan
    •  & Eilon Sherman
  • Article
    | Open Access

    Circular dorsal ruffles (CDRs) are important for the vesicular uptake of extracellular matter, but the basis of their wave dynamics is not understood. Here, the authors propose and experimentally test a bistable reaction-diffusion system, which they show accounts for the typical CDR expansion and shrinkage and for aberrant formation of pinned waves and spirals.

    • Erik Bernitt
    • , Hans-Günther Döbereiner
    •  & Arik Yochelis
  • Article
    | Open Access

    Cellular uptake of vitamin B12 (cobalamin) requires the binding of holo-transcobalamin (TC) from plasma by CD320. Here, the authors report the structure of a complex between CD320 and TC loaded with cyanocobalamin, alongside additional functional analysis.

    • Amer Alam
    • , Jae-Sung Woo
    •  & Kaspar P. Locher
  • Article
    | Open Access

    Cell shape is determined by a combination of biochemical regulation and mechanical forces. By imaging the dynamic behaviour of growth regulatory proteins in fission yeast and integrating these data within a mechanical model, Abenza et al. find that exocytosis plays a dominant role in shaping growth domains.

    • Juan F. Abenza
    • , Etienne Couturier
    •  & Rafael E. Carazo Salas
  • Article
    | Open Access

    Ion channels are often an assembly of proteins, but it is not clear if protein combinations have additive effects or function to prevent binding of other proteins. Here, the authors show that β and γ subunits can assemble into the same BK complex, and the constituents of the complex have an effect on its function.

    • Vivian Gonzalez-Perez
    • , Xiao-Ming Xia
    •  & Christopher J. Lingle
  • Article
    | Open Access

    The proapoptotic protein Bax triggers cell death by forming pores in the outer mitochondrial membrane. Using single-particle TIRF imaging, the authors show that Bax binds the membrane in a monomeric state before forming dimers and multimers of dimers, which are disassembled by the survival protein Bcl-xL.

    • Yamunadevi Subburaj
    • , Katia Cosentino
    •  & Ana J. García-Sáez
  • Article
    | Open Access

    Proteins that bend membranes often contain curvature-promoting structural motifs such as wedges or crescent-shaped domains. Busch et al.report that intrinsically disordered domains can also drive membrane curvature and provide evidence that steric pressure driven by protein crowding mediates this effect.

    • David J. Busch
    • , Justin R. Houser
    •  & Jeanne C. Stachowiak
  • Article
    | Open Access

    Variations in cell shape must be accommodated by the cell membrane, but how the membrane adjusts to changes in area and volume is not known. Here the authors show that the membrane responds in a nearly instantaneous, purely physical manner involving the flattening or generation of membrane invaginations.

    • Anita Joanna Kosmalska
    • , Laura Casares
    •  & Pere Roca-Cusachs
  • Article
    | Open Access

    BAR domain proteins are known to reshape cell membranes. Using coarse-grained molecular dynamics simulations, Simunovic and Voth demonstrate that membrane tension strongly affects the association of BAR proteins, in turn controlling their recruitment to membrane-remodelling sites.

    • Mijo Simunovic
    •  & Gregory A. Voth
  • Article
    | Open Access

    In bacteria, type III secretion systems (T3SS) allow the direct transport of protein across membranes, and related elements of a sorting platform facilitate hierarchical secretion of protein substrates. Here, the authors illustrate the mechanism of selective assembly of the T3SS sorting platforms in injectisome and flagellar systems.

    • Ryan Q. Notti
    • , Shibani Bhattacharya
    •  & C. Erec Stebbins
  • Article
    | Open Access

    FMNL formins polymerize actin filaments to generate cellular protrusions such as lamellipodia and filopodia at the leading edge of a cell. Here the authors provide detailed mechanistic insights into the formation of actin-based protrusions through GTPase dependent activation and membrane localization of FMNL1 and FMNL2.

    • Sonja Kühn
    • , Constanze Erdmann
    •  & Matthias Geyer
  • Article |

    The existence of membrane rafts of higher lipid order in living cells is subject to ongoing debate. Here, Sevcsik et al. use a micropatterning approach to show that glycosylphosphatidylinositol-anchored proteins, typical raft constituents, do not influence their membrane nanoenvironment to promote raft phase formation.

    • Eva Sevcsik
    • , Mario Brameshuber
    •  & Gerhard J. Schütz
  • Article |

    Lysosomal phospholipase A2 (LPLA2) and lecithin:cholesterol acyltransferase (LCAT) are important lipid metabolizing enzymes. Here the authors present crystal structures of LPLA2 and LCAT that reveal the unique architecture of this small family of enzymes involved in human physiology and disease.

    • Alisa Glukhova
    • , Vania Hinkovska-Galcheva
    •  & John J. G. Tesmer
  • Article
    | Open Access

    Actinoporins are water-soluble pore-forming toxins that self-assemble in the membranes of target cells. Here, the authors provide insight into the mechanism of membrane pore formation by solving the structures of several states of the hemolytic protein fragaceatoxin C, including the fully assembled pore.

    • Koji Tanaka
    • , Jose M.M. Caaveiro
    •  & Kouhei Tsumoto
  • Article
    | Open Access

    Pore-forming toxins are expressed as monomers and assemble into multimeric pores. Here, Benke et al. follow the kinetics of pore formation for the bacterial toxin ClyA with single-molecule methods and show that pore formation progresses through the assembly of oligomeric intermediates, rather than by the addition of monomers to a nascent pore.

    • Stephan Benke
    • , Daniel Roderer
    •  & Benjamin Schuler
  • Article
    | Open Access

    The earliest steps in autophagy are thought to include the budding of Atg16L-containing vesicles from the plasma membrane and their homotypic fusion to form a phagophore. Morozova et al. reveal a role for the membrane curvature-inducing protein Annexin A2 in the formation and fusion of these vesicles.

    • Kateryna Morozova
    • , Sunandini Sidhar
    •  & Laura Santambrogio
  • Article
    | Open Access

    SWEET family proteins mediate cellular sugar efflux and exchange through a facilitative diffusion mechanism. Here, Lee et al. shed light on the overall sugar transport cycle of the SemiSWEET uniporter-based structures trapped in both the inward-facing and outward-facing conformations.

    • Yongchan Lee
    • , Tomohiro Nishizawa
    •  & Osamu Nureki
  • Article |

    Matrix metalloprotease-12 is secreted by macrophages during the inflammatory response, but was reported to be active near cell surfaces. Koppisetti et al.reveal the enzyme’s unprecedented use of two distinct surfaces to interact with lipid bilayers, thereby targeting it to cellular membranes.

    • Rama K. Koppisetti
    • , Yan G. Fulcher
    •  & Steven R. Van Doren