Biophysical chemistry

  • Article
    | Open Access

    Nuclear import receptors (NIRs) regulate self-association of RNA-binding proteins as phase modifiers, while C9orf72-derived arginine-rich polydipeptides lead to aberrant phase transitions. Here the authors show in molecular basis how arginine-rich poly-dipeptides impede the ability of NIRs, particularly Kapβ2.

    • Hitoki Nanaura
    • , Honoka Kawamukai
    •  & Eiichiro Mori
  • Article
    | Open Access

    Here, the authors use solid-state NMR and EPR measurements to characterise the ATP hydrolysis transition state of the oligomeric bacterial DnaB helicase from Helicobacter pylori, which was trapped by using aluminium fluoride as a chemical mimic. They identify protein protons that coordinate to the phosphate groups of ADP and DNA and observe that the aluminium fluoride unit is highly mobile and fast-rotating.

    • Alexander A. Malär
    • , Nino Wili
    •  & Thomas Wiegand
  • Article
    | Open Access

    The analysis of NMR spectra of complex biochemical samples with respect to individual resonances is challenging but critically important. Here, the authors present a deep learning-based method that accelerates this process also for crowded NMR data that are non-trivial to analyze, even by expert NMR spectroscopists.

    • Da-Wei Li
    • , Alexandar L. Hansen
    •  & Rafael Brüschweiler
  • Article
    | Open Access

    Aβ oligomers (AβO) are thought to represent the main toxic species in Alzheimer’s disease but very high Aβ concentrations are required to study them in vitro and it remains unknown what role these off-pathway oligomers play in vivo. Here, the authors use a dimeric variant of Aβ termed dimAβ, where two Aβ40 units are linked, which facilitates to study AβO formation kinetics and they observe that Aβ off-pathway oligomer formation is strongly accelerated at endo-lysosomal pH, while amyloid fibril formation is delayed. Furthermore, the authors demonstrate that dimAβ is a disease-relevant model construct for pathogenic AβO formation by showing that dimAβ AβOs target dendritic spines and induce AD-like somatodendritic Tau missorting.

    • Marie P. Schützmann
    • , Filip Hasecke
    •  & Wolfgang Hoyer
  • Article
    | Open Access

    The histone acetyltransferase p300 mostly localizes to active chromatin; however, some repressed genes marked with H3K27me3 are also bound by p300. Here the authors show p300 is capable of phase separation, which relies on its catalytic core, and that p300 catalytic activity is decreased in phase-separated droplets that co-localize with H3K27me3-marked chromatin.

    • Yi Zhang
    • , Kyle Brown
    •  & Tatiana G. Kutateladze
  • Article
    | Open Access

    The membrane is an integral component of the G protein-coupled receptor signaling machinery. Here authors demonstrate that lipids regulate the signaling efficacy and selectivity of the ghrelin receptor GHSR through specific interactions and bulk effects and observe PIP2 and GM3 induced shifts of the conformational equilibrium of GHSR away from its inactive state.

    • Marjorie Damian
    • , Maxime Louet
    •  & Jean-Louis Banères
  • Article
    | Open Access

    The authors generated a Synthetic Morphogenic Membrane System by encapsulating a dynamic microtubule aster and a light-inducible signaling system driven by GTP/ATP chemical potential into cell-sized liposomes. This reconstitution of artificial proto-cells reveals how non-equilibrium phenomena affect cellular information processing in morphogenesis.

    • Konstantin Gavriljuk
    • , Bruno Scocozza
    •  & Philippe I. H. Bastiaens
  • Article
    | Open Access

    Ice-nucleating proteins promote ice formation at high sub-zero temperatures, but the mechanism is still unclear. The authors investigate a model ice-nucleating protein at the air-water interface using vibrational sum frequency generation spectroscopy and simulations, revealing its reorientation at low temperatures, which increases contact with water molecules and promotes their ordering.

    • Steven J. Roeters
    • , Thaddeus W. Golbek
    •  & Tobias Weidner
  • Article
    | Open Access

    Elucidating the molecular driving forces underlying liquid–liquid phase separation is a key objective for understanding biological function and malfunction. Here the authors show that a wide range of cellular proteins, including FUS, TDP-43, Brd4, Sox2, and Annexin A11, which form condensates at low salt concentrations, can reenter a phase-separated regime at high salt concentrations.

    • Georg Krainer
    • , Timothy J. Welsh
    •  & Tuomas P. J. Knowles
  • Article
    | Open Access

    The high potential iron-sulfur (HiPIP) proteins are direct electron donors to the light-harvesting-reaction center complexes (LH1-RC) in photosynthetic β- and γ-Proteobacteria. Here, the authors present the 2.9 Å crystal structure of the HiPIP-bound LH1-RC complex from the thermophilic purple sulfur bacterium Thermochromatium tepidum and discuss mechanistic implications for the electron transfer pathway.

    • Tomoaki Kawakami
    • , Long-Jiang Yu
    •  & Zheng-Yu Wang-Otomo
  • Article
    | Open Access

    The dissociation mechanism of the heme axial ligand in heme proteins is not yet fully understood. The authors investigate the photodissociation dynamics of the bond between heme Fe and methionine S in ferrous cytochrome c using femtosecond time-resolved X-ray solution scattering and X-ray emission spectroscopy, simultaneously tracking electronic and nuclear structure changes.

    • Marco E. Reinhard
    • , Michael W. Mara
    •  & Kelly J. Gaffney
  • Article
    | Open Access

    Coiled-coil protein origami (CCPO) is a strategy for the design of polyhedral cage-shaped protein folds based on coiled-coil (CC) dimer-forming peptides. Here, the authors show that CCPO proteins fold in a multistep process governed by the spatial distance between CC modules in the primary sequence and subsequent folding intermediates, which enables the use of identical CC modules for the CCPO tetrahedron design.

    • Jana Aupič
    • , Žiga Strmšek
    •  & Roman Jerala
  • Article
    | Open Access

    Reactive oxygen species (ROS) production by reverse electron transfer (RET) through complex I is thought to cause tissue damage from heart attacks. Here, the authors combine in vivo work with biochemical and cryo-EM analyses to characterize the effects of a P25L mutation in the ND6 subunit of mitochondrial complex I. They observe that this mutation does not affect oxidative phosphorylation but renders complex I unable to generate ROS by RET: ND6-P25L mice are protected against cardiac ischaemia–reperfusion injury, thus providing evidence for the proposed role of ROS production in myocardial infarction.

    • Zhan Yin
    • , Nils Burger
    •  & Judy Hirst
  • Article
    | Open Access

    The small proton-coupled transporter EmrE confers multidrug resistance in bacteria. The structure of drug-bound EmrE in phospholipid bilayers is now determined using solid-state NMR. The structure provides detailed insights into the molecular mechanism of substrate recognition by this transporter.

    • Alexander A. Shcherbakov
    • , Grant Hisao
    •  & Mei Hong
  • Article
    | Open Access

    Short cationic peptides and nucleotides can form complex coacervates, but the influence of reduced multivalency on coacervate functionality was not investigated. Here, the authors report that coacervates formed from short polyions generate distinct pH microenvironments, accumulate RNA and preserve nucleic acid duplexes more efficiently than their longer counterparts.

    • Fatma Pir Cakmak
    • , Saehyun Choi
    •  & Christine D. Keating
  • Article
    | Open Access

    Almost all allosteric systems are large multi-domain proteins which complicates the investigation of the mechanism in atomistic detail. Here authors designed a small allosteric protein system using the photocontrollable PDZ3 domain, that allows controlling allostery between the binding and allosteric site in both directions.

    • Olga Bozovic
    • , Brankica Jankovic
    •  & Peter Hamm
  • Article
    | Open Access

    Membrane-less organelles or compartments are considered to be dynamic reaction centers for spatiotemporal control of diverse cellular processes. Here authors report quantitative measurements of changes in protein interactions for the proteins recruited into membrane-less compartments (termed client proteins) in living cells.

    • Daesun Song
    • , Yongsang Jo
    •  & Yongwon Jung
  • Article
    | Open Access

    Rhodopsin phosphodiesterase (Rh-PDE) hydrolyzes both cAMP and cGMP in a light-dependent manner. Structural and functional analyses of the Rh-PDE from Salpingoeca rosetta reveal unusual rhodopsin topology comprising 8 transmembrane helices (TMs) and suggest that TM0 plays a crucial role in the enzymatic photoactivity.

    • Tatsuya Ikuta
    • , Wataru Shihoya
    •  & Osamu Nureki
  • Article
    | Open Access

    The xrRNA1 RNA from ZIKA virus (ZIKV) forms a complex ring-like architecture and is known for its mechanical anisotropy, but the mechanism for its direction-dependent mechanical responses remain unclear. Here authors use a single-molecule nanopore sensing technique combined with molecular dynamics simulations and show that the anisotropy in ZIKV xrRNA1 depends on Mg2+ and the key tertiary interactions.

    • Xiaolin Niu
    • , Qiuhan Liu
    •  & Xianyang Fang
  • Article
    | Open Access

    Here, the authors present an approach that enhances the sensitivity of basic 2D biomolecular NMR experiments like NOESY and TOCSY, when carried out in polysaccharides, proteins and nucleic acids. This method combines principles associated to quantum Anti-Zeno Effects and advanced data acquisition methods based on Hadamard multiplexing.

    • Mihajlo Novakovic
    • , Ēriks Kupče
    •  & Lucio Frydman
  • Article
    | Open Access

    Multivalent ligand-receptor interactions enhance binding selectivity in biological systems, and may be exploited to design synthetic systems. Here the authors demonstrate a multivalent behavior where the ability to bind the target occurs when the receptor density is within a specific range.

    • Meng Liu
    • , Azzurra Apriceno
    •  & Stefano Angioletti-Uberti
  • Article
    | Open Access

    The design principles underlying biomolecular phase separation of membrane-less organelles remain poorly understood. Using model homopolymers, Fisher et al. show that the formation kinetics of coexisting liquid phases can be tuned by exploiting differences between arginine and lysine residues.

    • Rachel S. Fisher
    •  & Shana Elbaum-Garfinkle
  • Article
    | Open Access

    SARS-CoV-2 spike protein binds host ACE2 for virus entry. Here, the authors determine kinetic and thermodynamic properties of this interaction using atomic force microscopy, develop peptides that inhibit binding and suggest existence of additional attachment factors.

    • Jinsung Yang
    • , Simon J. L. Petitjean
    •  & David Alsteens
  • Article
    | Open Access

    The change from low-spin hexacoordinated to high-spin pentacoordinated domed form in heam upon ligand detachment and the reverse process underlie the respiratory function. The authors, using femtosecond time-resolved X-ray emission spectroscopy, capture the transient states connecting the two forms in myoglobin-NO upon NO photoinduced detachment.

    • Dominik Kinschel
    • , Camila Bacellar
    •  & Majed Chergui
  • Article
    | Open Access

    G-quadruplex (G4) forming sequences are highly enriched in the human genome and function as important regulators of diverse range of biological processes. Here the authors show that while G4 structures on template strand block transcription, folding on the non-template strand enhances transcription by means of successive R-loop formation.

    • Chun-Ying Lee
    • , Christina McNerney
    •  & Sua Myong
  • Article
    | Open Access

    While infrared nanospectroscopy methods based on thermomechanical detection (AFM-IR) enables the acquisition of absorption spectra at the nanoscale, single molecule detection has not been possible so far. Here, the authors present off-resonance, low power and short pulse infrared nanospectroscopy (ORS-nanoIR), which allows measuring infrared absorption spectra at the single molecule level in a time scale of seconds with high throughput and demonstrate that the secondary structure of single protein molecules can be determined with this method.

    • Francesco Simone Ruggeri
    • , Benedetta Mannini
    •  & Tuomas P. J. Knowles
  • Article
    | Open Access

    ESCRT-III proteins assemble into ubiquitous membrane-remodeling polymers during many cellular processes. Here, the authors use cryo-ET, cryo-EM and mathematical modeling to reveal how the shape of the helical membrane tube arises from the assembly of two distinct bundles of helical filaments.

    • Joachim Moser von Filseck
    • , Luca Barberi
    •  & Aurélien Roux
  • Article
    | Open Access

    Chromatin remodellers hydrolyse ATP to move nucleosomal DNA against histone octamers. Here, the authors use single-molecule assays to examine the mechanism of action of CHD4 remodeller, and provide evidence that CHD4 slides nucleosomes by decoupling entry- and exit-side DNA translocation.

    • Yichen Zhong
    • , Bishnu P. Paudel
    •  & Joel P. Mackay
  • Article
    | Open Access

    Proper membrane physiology requires maintenance of a narrow range of physicochemical properties, which must be buffered from external perturbations. Here, authors report lipidomic remodeling to preserve membrane physical properties upon exogenous polyunsaturated fatty acids exposure.

    • Kandice R. Levental
    • , Eric Malmberg
    •  & Ilya Levental
  • Article
    | Open Access

    Bilaterian mitochondria-encoded tRNA genes accumulate mutations at higher rates than their cytoplasmic tRNA counterparts, resulting in idiosyncratic structures. Here the authors suggest an evolutionary basis for the observed mutational freedom of mitochondrial (mt) tRNAs and reveal the associated co-adaptive structural and functional changes in mt aminoacyl-tRNA synthetases.

    • Bernhard Kuhle
    • , Joseph Chihade
    •  & Paul Schimmel
  • Article
    | Open Access

    To carry out their function, transcription factors must efficiently recognize specific DNA sequence targets, a complex problem in the context of eukaryotic chromatin. Here the authors use single-molecule biophysical experiments, statistical mechanical theory and bioinformatics analyses to conclude that interactions with non-target sequences near promoters serve to increase overall affinity and targeting efficiency.

    • Milagros Castellanos
    • , Nivin Mothi
    •  & Victor Muñoz
  • Article
    | Open Access

    Many RNA systems possess highly ordered 3-D structures that are essential to their function. Here the authors demonstrate that the long non-coding RNA Braveheart possesses a flexible but defined 3-D structure which is remodeled upon binding the protein CNBP.

    • Doo Nam Kim
    • , Bernhard C. Thiel
    •  & Karissa Y. Sanbonmatsu
  • Article
    | Open Access

    Mobile group II introns function as ribozymes to splice and reinsert themselves into DNA, thereby colonizing new genomic regions. Here the authors use single-molecule FRET and molecular dynamics simulations to reveal a structural link between metal ion induced kinetic heterogeneity and the sugar puckers at the exon-intron binding interface.

    • Fabio D. Steffen
    • , Mokrane Khier
    •  & Roland K. O. Sigel
  • Article
    | Open Access

    Liquid-liquid phase separation (LLPS) of intrinsically disordered proteins plays an important part in the formation of extracellular biological materials. Here, the authors show that repeats of the peptide motif GHGLY are necessary for the LLPS of pH-responsive histidine-rich squid beak proteins.

    • Bartosz Gabryelczyk
    • , Hao Cai
    •  & Ali Miserez
  • Article
    | Open Access

    Nanopores have a wide range of applications in the field of sensing. Here the authors report on synthetic nanopores made of DNA and designed for the transit of folded proteins across membranes to allow for biosensing.

    • Tim Diederichs
    • , Genevieve Pugh
    •  & Stefan Howorka
  • Article
    | Open Access

    Metal-mediated base pairs expand the repertoire of nucleic acid structures and dynamics. Here, the authors prepared a metallo-DNA duplex including two C-Hg(II)-T base pairs separated by six normal Watson-Crick base pairs and investigated its solution structure and dynamics using NMR spectroscopy.

    • Olivia P. Schmidt
    • , Simon Jurt
    •  & Nathan W. Luedtke
  • Article
    | Open Access

    Activatable fluorophores are of interest for a wide range of applications but the need for caging groups complicates their development and application. Here, the authors report on a photoactivatable silicon rhodamine derivative and its application in live cell imaging and single-particle tracking.

    • Michelle S. Frei
    • , Philipp Hoess
    •  & Kai Johnsson
  • Article
    | Open Access

    Understanding the fusion of nanocarriers with cell membranes is important to the design of effective drug delivery methods. Here, the authors report on a study into the fusion of cubosomes with model cell membranes underflow conditions and report on the binding kinetics.

    • Brendan P. Dyett
    • , Haitao Yu
    •  & Charlotte E. Conn
  • Article
    | Open Access

    Argonaute protein is loaded with small RNA and scans long stretch of sequences to find complementary target sites. Here, using single-molecule FRET and kinetic modelling, the authors showed that prokaryotic Argonaute protein binds target DNA loosely and slides along the DNA during target search.

    • Tao Ju Cui
    • , Misha Klein
    •  & Chirlmin Joo
  • Article
    | Open Access

    Many animals use the Earth’s magnetic field for orientation, yet the underlying principles are poorly understood. The authors show that a molecular triad acts as a chemical compass in magnetic fields of similar magnitude to that of the Earth, supporting the hypothesis that photo-initiated quantum processes underlie bird magnetoreception.

    • Christian Kerpal
    • , Sabine Richert
    •  & Christiane R. Timmel
  • Article
    | Open Access

    The ability to encapsulate living cells could lead to many applications. Here, the authors present a flexible method to graft DNA polymers onto bacteria, yeast and mammalian cells, polymerize them into DNA cocoons and use these to manipulate and select cells based on the encoded polymer sequences on DNA cocoons.

    • Tao Gao
    • , Tianshu Chen
    •  & Genxi Li
  • Article
    | Open Access

    The SLC26 family of transporters maintains anion equilibria in all kingdoms of life. Here, the authors resolve the structure of an SLC26 dimer embedded in a lipid membrane and characterize it by PELDOR/DEER distance measurements, biochemical studies with MD simulations and spin-label ensemble refinement.

    • Yung-Ning Chang
    • , Eva A. Jaumann
    •  & Eric R. Geertsma
  • Article
    | Open Access

    Polyglutamine (polyQ) tracts are low-complexity regions and their expansion is linked to certain neurodegenerative diseases. Here the authors combine experimental and computational approaches to find that the length of the androgen receptor polyQ tract correlates with its helicity and show that the polyQ helical structure is stabilized by hydrogen bonds between the Gln side chains and main chain carbonyl groups.

    • Albert Escobedo
    • , Busra Topal
    •  & Xavier Salvatella