bims-strubi Biomed News
on Advances in structural biology
Issue of 2021‒12‒12
seventeen papers selected by
Alessandro Grinzato
European Synchrotron Radiation Facility
  1. Cryo-EM structures of human RNA polymerase I.
  2. Structure, mechanism, and inhibition of Hedgehog acyltransferase.
  3. Cryo-EM reveals unique structural features of the FhuCDB Escherichia coli ferrichrome importer.
  4. Structural and molecular basis for Cardiovirus 2A protein as a viral gene expression switch.
  5. Entropy-regularized deconvolution of cellular cryotransmission electron tomograms.
  6. Preparation and Cryo-FIB micromachining of Saccharomyces cerevisiae for Cryo-Electron Tomography.
  7. iNEXT-Discovery and Instruct-ERIC: Integrating High-End Services for Translational Research in Structural Biology.
  8. Benchmarking the ideal sample thickness in cryo-EM.
  9. Dimeric and high-resolution structures of Chlamydomonas Photosystem I from a temperature-sensitive Photosystem II mutant.
  10. Architecture of the chloroplast PSI-NDH supercomplex in Hordeum vulgare.
  11. Sliding of HIV-1 reverse transcriptase over DNA creates a transient P pocket - targeting P-pocket by fragment screening.
  12. Structural basis for transthyretin amyloid formation in vitreous body of the eye.
  13. Recent High-Resolution Structures of Amyloids Involved in Neurodegenerative Diseases.
  14. The cryo-EM structure of the human neurofibromin dimer reveals the molecular basis for neurofibromatosis type 1.
  15. Structural basis of inhibition of the human SGLT2-MAP17 glucose transporter.
  16. Structure of pathological TDP-43 filaments from ALS with FTLD.
  17. Structure and mechanism of the SGLT family of glucose transporters.
  1. Nat Struct Mol Biol. 2021 Dec;28(12): 997-1008
    Cryo-EM structures of human RNA polymerase I.
    Agata D Misiaszek, Mathias Girbig, Helga Grötsch, Florence Baudin, Brice Murciano, Aleix Lafita, Christoph W Müller.
      RNA polymerase I (Pol I) specifically synthesizes ribosomal RNA. Pol I upregulation is linked to cancer, while mutations in the Pol I machinery lead to developmental disorders. Here we report the cryo-EM structure of elongating human Pol I at 2.7 Å resolution. In the exit tunnel, we observe a double-stranded RNA helix that may support Pol I processivity. Our structure confirms that human Pol I consists of 13 subunits with only one subunit forming the Pol I stalk. Additionally, the structure of human Pol I in complex with the initiation factor RRN3 at 3.1 Å resolution reveals stalk flipping upon RRN3 binding. We also observe an inactivated state of human Pol I bound to an open DNA scaffold at 3.3 Å resolution. Lastly, the high-resolution structure of human Pol I allows mapping of disease-related mutations that can aid understanding of disease etiology.
    DOI:  https://doi.org/10.1038/s41594-021-00693-4
  2. Mol Cell. 2021 Dec 07. pii: S1097-2765(21)00998-9. [Epub ahead of print]
    Structure, mechanism, and inhibition of Hedgehog acyltransferase.
    Claire E Coupland, Sebastian A Andrei, T Bertie Ansell, Loic Carrique, Pramod Kumar, Lea Sefer, Rebekka A Schwab, Eamon F X Byrne, Els Pardon, Jan Steyaert, Anthony I Magee, Thomas Lanyon-Hogg, Mark S P Sansom, Edward W Tate, Christian Siebold.
      The Sonic Hedgehog (SHH) morphogen pathway is fundamental for embryonic development and stem cell maintenance and is implicated in various cancers. A key step in signaling is transfer of a palmitate group to the SHH N terminus, catalyzed by the multi-pass transmembrane enzyme Hedgehog acyltransferase (HHAT). We present the high-resolution cryo-EM structure of HHAT bound to substrate analog palmityl-coenzyme A and a SHH-mimetic megabody, revealing a heme group bound to HHAT that is essential for HHAT function. A structure of HHAT bound to potent small-molecule inhibitor IMP-1575 revealed conformational changes in the active site that occlude substrate binding. Our multidisciplinary analysis provides a detailed view of the mechanism by which HHAT adapts the membrane environment to transfer an acyl chain across the endoplasmic reticulum membrane. This structure of a membrane-bound O-acyltransferase (MBOAT) superfamily member provides a blueprint for other protein-substrate MBOATs and a template for future drug discovery.
    Keywords:  Hedgehog acyl transferase; Sonic Hedgehog signaling; cryo-EM structure; drug; heme; integral membrane protein; membrane-bound O-acyltransferase; molecular dynamics simulations; palmitoyl co enzyme A; small molecule inhibitor
    DOI:  https://doi.org/10.1016/j.molcel.2021.11.018
  3. Commun Biol. 2021 Dec 09. 4(1): 1383
    Cryo-EM reveals unique structural features of the FhuCDB Escherichia coli ferrichrome importer.
    Wenxin Hu, Hongjin Zheng.
      As one of the most elegant biological processes developed in bacteria, the siderophore-mediated iron uptake demands the action of specific ATP-binding cassette (ABC) importers. Although extensive studies have been done on various ABC importers, the molecular basis of these iron-chelated-siderophore importers are still not fully understood. Here, we report the structure of a ferrichrome importer FhuCDB from Escherichia coli at 3.4 Å resolution determined by cryo electron microscopy. The structure revealed a monomeric membrane subunit of FhuB with a substrate translocation pathway in the middle. In the pathway, there were unique arrangements of residues, especially layers of methionines. Important residues found in the structure were interrogated by mutagenesis and functional studies. Surprisingly, the importer's ATPase activity was decreased upon FhuD binding, which deviated from the current understanding about bacterial ABC importers. In summary, to the best of our knowledge, these studies not only reveal a new structural twist in the type II ABC importer subfamily, but also provide biological insights in the transport of iron-chelated siderophores.
    DOI:  https://doi.org/10.1038/s42003-021-02916-2
  4. Nat Commun. 2021 Dec 09. 12(1): 7166
    Structural and molecular basis for Cardiovirus 2A protein as a viral gene expression switch.
    Chris H Hill, Lukas Pekarek, Sawsan Napthine, Anuja Kibe, Andrew E Firth, Stephen C Graham, Neva Caliskan, Ian Brierley.
      Programmed -1 ribosomal frameshifting (PRF) in cardioviruses is activated by the 2A protein, a multi-functional virulence factor that also inhibits cap-dependent translational initiation. Here we present the X-ray crystal structure of 2A and show that it selectively binds to a pseudoknot-like conformation of the PRF stimulatory RNA element in the viral genome. Using optical tweezers, we demonstrate that 2A stabilises this RNA element, likely explaining the increase in PRF efficiency in the presence of 2A. Next, we demonstrate a strong interaction between 2A and the small ribosomal subunit and present a cryo-EM structure of 2A bound to initiated 70S ribosomes. Multiple copies of 2A bind to the 16S rRNA where they may compete for binding with initiation and elongation factors. Together, these results define the structural basis for RNA recognition by 2A, show how 2A-mediated stabilisation of an RNA pseudoknot promotes PRF, and reveal how 2A accumulation may shut down translation during virus infection.
    DOI:  https://doi.org/10.1038/s41467-021-27400-7
  5. Proc Natl Acad Sci U S A. 2021 Dec 14. pii: e2108738118. [Epub ahead of print]118(50):
    Entropy-regularized deconvolution of cellular cryotransmission electron tomograms.
    Matthew Croxford, Michael Elbaum, Muthuvel Arigovindan, Zvi Kam, David Agard, Elizabeth Villa, John Sedat.
      Cryo-electron tomography (cryo-ET) allows for the high-resolution visualization of biological macromolecules. However, the technique is limited by a low signal-to-noise ratio (SNR) and variance in contrast at different frequencies, as well as reduced Z resolution. Here, we applied entropy-regularized deconvolution (ER-DC) to cryo-ET data generated from transmission electron microscopy (TEM) and reconstructed using weighted back projection (WBP). We applied deconvolution to several in situ cryo-ET datasets and assessed the results by Fourier analysis and subtomogram analysis (STA).
    Keywords:  cryo-electron tomography; deconvolution; missing wedge; structural biology; subtomogram analysis
    DOI:  https://doi.org/10.1073/pnas.2108738118
  6. J Vis Exp. 2021 Nov 20.
    Preparation and Cryo-FIB micromachining of Saccharomyces cerevisiae for Cryo-Electron Tomography.
    Jana Moravcová, Matyáš Pinkas, Radka Holbová, Jiří Nováček.
      Today, cryo-electron tomography (cryo-ET) is the only technique that can provide near-atomic resolution structural data on macromolecular complexes in situ. Owing to the strong interaction of an electron with the matter, high-resolution cryo-ET studies are limited to specimens with a thickness of less than 200 nm, which restricts the applicability of cryo-ET only to the peripheral regions of a cell. A complex workflow that comprises the preparation of thin cellular cross-sections by cryo-focused ion beam micromachining (cryo-FIBM) was introduced during the last decade to enable the acquisition of cryo-ET data from the interior of larger cells. We present a protocol for the preparation of cellular lamellae from a sample vitrified by plunge freezing utilizing Saccharomyces cerevisiae as a prototypical example of a eukaryotic cell with wide utilization in cellular and molecular biology research. We describe protocols for vitrification of S. cerevisiae into isolated patches of a few cells or a continuous monolayer of the cells on a TEM grid and provide a protocol for lamella preparation by cryo-FIB for these two samples.
    DOI:  https://doi.org/10.3791/62351
  7. J Vis Exp. 2021 Nov 16.
    iNEXT-Discovery and Instruct-ERIC: Integrating High-End Services for Translational Research in Structural Biology.
    Hans Wienk, Lucia Banci, Susan Daenke, Eva Pereiro, Harald Schwalbe, David Ian Stuart, Manfred S Weiss, Anastassis Perrakis.
      ARTICLES DISCUSSED: Ahmad, M. U. D. et al. Nano-differential scanning fluorimetry for screening in fragment-based lead discovery. Journal of Visualized Experiments: JoVE. (171), e62469 (2021). Barbieri, L., Luchinat, E. Monitoring protein-ligand interactions in human cells by real-time quantitative in-cell NMR using a high cell density bioreactor. Journal of Visualized Experiments: JoVE. (169), e62323 (2021). Berg, H. et al. NMR-based fragment screening in a minimum sample but maximum automation mode. Journal of Visualized Experiments: JoVE. (172), e62262 (2021). Beriashvili, D., Schellevis, R. D., Napoli, F., Weingarth, M., Baldus, M. High-resolution studies of proteins in natural membranes by solid-state NMR. Journal of Visualized Experiments: JoVE. (169), e62197 (2021). Cornaciu, I. et al. The automated crystallography pipelines at the EMBL HTX facility in grenoble. Journal of Visualized Experiments: JoVE. (172), e62200 (2021). Crawshaw, A. et al. A sample preparation pipeline for microcrystals at the VMXm beamline. Journal of Visualized Experiments: JoVE. (172), e62306 (2021). Douangamath, A. et al. Achieving efficient fragment screening at XChem facility at diamond light source. Journal of Visualized Experiments: JoVE. (171), e62414 (2021). Groen, J. et al. A 3D cartographic description of the cell by Cryo Soft X-ray tomography. Journal of Visualized Experiments: JoVE. (169), e62190 (2021). Horrell, S. et al. Fixed target serial data collection at diamond light source. Journal of Visualized Experiments: JoVE. (168), e62491 (2021). Jiménez-Moreno, A. et al. Cryo-EM and single-particle analysis with scipion. Journal of Visualized Experiments: JoVE. (171), e62261 (2021). Moravcová, J., Pinkas, M., Holbová, R., Nováček, J. Preparation and CryoFIB micromachining of Saccharomyces cerevisiae for CryoElectron tomography. Journal of Visualized Experiments: JoVE. e62351 (2021). Vyas, N. et al. Cryo-structured illumination microscopic data collection from cryogenically preserved cells. Journal of Visualized Experiments: JoVE. (171), e62274 (2021). Weis, F., Hagen, W. J. H., Schorb, M., Mattei, S. Strategies for optimization of cryogenic electron tomography data acquisition. Journal of Visualized Experiments: JoVE. (169), e62383 (2021). White, J. B. R. et al. Single particle cryo-electron microscopy: From sample to structure. Journal of Visualized Experiments: JoVE. (171), e62415 (2021). Wollenhaupt, J. et al. Workflow and tools for crystallographic fragment screening at the helmholtz-zentrum Berlin. Journal of Visualized Experiments: JoVE. (169), e62208 (2021).
    DOI:  https://doi.org/10.3791/63435
  8. Proc Natl Acad Sci U S A. 2021 Dec 07. pii: e2108884118. [Epub ahead of print]118(49):
    Benchmarking the ideal sample thickness in cryo-EM.
    Michael W Martynowycz, Max T B Clabbers, Johan Unge, Johan Hattne, Tamir Gonen.
      The relationship between sample thickness and quality of data obtained is investigated by microcrystal electron diffraction (MicroED). Several electron microscopy (EM) grids containing proteinase K microcrystals of similar sizes from the same crystallization batch were prepared. Each grid was transferred into a focused ion beam and a scanning electron microscope in which the crystals were then systematically thinned into lamellae between 95- and 1,650-nm thick. MicroED data were collected at either 120-, 200-, or 300-kV accelerating voltages. Lamellae thicknesses were expressed in multiples of the corresponding inelastic mean free path to allow the results from different acceleration voltages to be compared. The quality of the data and subsequently determined structures were assessed using standard crystallographic measures. Structures were reliably determined with similar quality from crystalline lamellae up to twice the inelastic mean free path. Lower resolution diffraction was observed at three times the mean free path for all three accelerating voltages, but the data quality was insufficient to yield structures. Finally, no coherent diffraction was observed from lamellae thicker than four times the calculated inelastic mean free path. This study benchmarks the ideal specimen thickness with implications for all cryo-EM methods.
    Keywords:  Cryo-EM; FIB milling; MicroED; electron scattering; mean free path
    DOI:  https://doi.org/10.1073/pnas.2108884118
  9. Commun Biol. 2021 Dec 09. 4(1): 1380
    Dimeric and high-resolution structures of Chlamydomonas Photosystem I from a temperature-sensitive Photosystem II mutant.
    Ido Caspy, Tom Schwartz, Vinzenz Bayro-Kaiser, Mariia Fadeeva, Amit Kessel, Nir Ben-Tal, Nathan Nelson.
      Water molecules play a pivotal functional role in photosynthesis, primarily as the substrate for Photosystem II (PSII). However, their importance and contribution to Photosystem I (PSI) activity remains obscure. Using a high-resolution cryogenic electron microscopy (cryo-EM) PSI structure from a Chlamydomonas reinhardtii temperature-sensitive photoautotrophic PSII mutant (TSP4), a conserved network of water molecules - dating back to cyanobacteria - was uncovered, mainly in the vicinity of the electron transport chain (ETC). The high-resolution structure illustrated that the water molecules served as a ligand in every chlorophyll that was missing a fifth magnesium coordination in the PSI core and in the light-harvesting complexes (LHC). The asymmetric distribution of the water molecules near the ETC branches modulated their electrostatic landscape, distinctly in the space between the quinones and FX. The data also disclosed the first observation of eukaryotic PSI oligomerisation through a low-resolution PSI dimer that was comprised of PSI-10LHC and PSI-8LHC.
    DOI:  https://doi.org/10.1038/s42003-021-02911-7
  10. Nature. 2021 Dec 08.
    Architecture of the chloroplast PSI-NDH supercomplex in Hordeum vulgare.
    Liangliang Shen, Kailu Tang, Wenda Wang, Chen Wang, Hangjun Wu, Zhiyuan Mao, Shaoya An, Shenghai Chang, Tingyun Kuang, Jian-Ren Shen, Guangye Han, Xing Zhang.
      Chloroplast NADH dehydrogenase-like (NDH) complex is composed of at least 29 subunits and plays an important role in mediating photosystem I (PSI) cyclic electron transport (CET)1-3. It associates with PSI to form the PSI-NDH supercomplex to fulfill its function. Here we report cryo-electron microscopy structure of a PSI-NDH supercomplex from barley (Hordeum vulgare) at an overall resolution of 4.4 Å and local resolutions of 3.40 Å-3.88 Å for the PSI-LHCI and NDH sub-complexes. The result reveals that PSI-NDH is composed of two copies of PSI-LHCI and one NDH complex. Two monomeric LHCI proteins, Lhca5 and Lhca6, mediate the binding of two PSI complexes to NDH. Ten plant chloroplast specific NDH subunits are observed and their exact positions as well as their interactions with other subunits in NDH are elucidated. Taken together, this study provides a structural basis for further investigations on the functions and regulation of the PSI-NDH-dependent CET.
    DOI:  https://doi.org/10.1038/s41586-021-04277-6
  11. Nat Commun. 2021 Dec 08. 12(1): 7127
    Sliding of HIV-1 reverse transcriptase over DNA creates a transient P pocket - targeting P-pocket by fragment screening.
    Abhimanyu K Singh, Sergio E Martinez, Weijie Gu, Hoai Nguyen, Dominique Schols, Piet Herdewijn, Steven De Jonghe, Kalyan Das.
      HIV-1 reverse transcriptase (RT) slides over an RNA/DNA or dsDNA substrate while copying the viral RNA to a proviral DNA. We report a crystal structure of RT/dsDNA complex in which RT overstepped the primer 3'-end of a dsDNA substrate and created a transient P-pocket at the priming site. We performed a high-throughput screening of 300 drug-like fragments by X-ray crystallography that identifies two leads that bind the P-pocket, which is composed of structural elements from polymerase active site, primer grip, and template-primer that are resilient to drug-resistance mutations. Analogs of a fragment were synthesized, two of which show noticeable RT inhibition. An engineered RT/DNA aptamer complex could trap the transient P-pocket in solution, and structures of the RT/DNA complex were determined in the presence of an inhibitory fragment. A synthesized analog bound at P-pocket is further analyzed by single-particle cryo-EM. Identification of the P-pocket within HIV RT and the developed structure-based platform provide an opportunity for the design new types of polymerase inhibitors.
    DOI:  https://doi.org/10.1038/s41467-021-27409-y
  12. Nat Commun. 2021 Dec 08. 12(1): 7141
    Structural basis for transthyretin amyloid formation in vitreous body of the eye.
    Irina Iakovleva, Michael Hall, Melanie Oelker, Linda Sandblad, Intissar Anan, A Elisabeth Sauer-Eriksson.
      Amyloid transthyretin (ATTR) amyloidosis is characterized by the abnormal accumulation of ATTR fibrils in multiple organs. However, the structure of ATTR fibrils from the eye is poorly understood. Here, we used cryo-EM to structurally characterize vitreous body ATTR fibrils. These structures were distinct from previously characterized heart fibrils, even though both have the same mutation and type A pathology. Differences were observed at several structural levels: in both the number and arrangement of protofilaments, and the conformation of the protein fibril in each layer of protofilaments. Thus, our results show that ATTR protein structure and its assembly into protofilaments in the type A fibrils can vary between patients carrying the same mutation. By analyzing and matching the interfaces between the amino acids in the ATTR fibril with those in the natively folded TTR, we are able to propose a mechanism for the structural conversion of TTR into a fibrillar form.
    DOI:  https://doi.org/10.1038/s41467-021-27481-4
  13. Front Aging Neurosci. 2021 ;13 782617
    Recent High-Resolution Structures of Amyloids Involved in Neurodegenerative Diseases.
    Rodrigo Diaz-Espinoza.
      Amyloids are highly ordered aggregates composed of proteins or peptides. They are involved in several pathologies, including hallmark neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's (PD). Individuals affected by these diseases accumulate in their brains amyloids inclusions composed of misfolded forms of a peptide (Aβ) and a protein (Tau) in AD and α-synuclein protein (α-Sn) in PD. Tau and α-Sn aggregates are also present in other neurodegenerative diseases. The insoluble nature and heterogeneity of amyloids have hampered their study at the molecular level. However, the use of solid state NMR and Cryogenic-electron microscopy along with fine-tuned modulation of the aggregation in vitro and improved isolation methods of brain-derived amyloids has allowed the elucidation of these elusive conformations at high resolution. In this work, we review the latest progress on the recent amyloid structures reported for Aβ, Tau, and α-Sn. The two-fold symmetry emerges as a convergent feature in the tridimensional arrangement of the protofilaments in the fibrillary structure of these pathological amyloids, with many of them exhibiting a Greek-key topology as part of their overall architecture. These specific features can serve as novel guides to seek potential molecular targets in drug design efforts.
    Keywords:  Aβ; Tau; amyloid; misfolding; neurodegenerative diseases; structure; α-Sn
    DOI:  https://doi.org/10.3389/fnagi.2021.782617
  14. Nat Struct Mol Biol. 2021 Dec;28(12): 982-988
    The cryo-EM structure of the human neurofibromin dimer reveals the molecular basis for neurofibromatosis type 1.
    Christopher J Lupton, Charles Bayly-Jones, Laura D'Andrea, Cheng Huang, Ralf B Schittenhelm, Hari Venugopal, James C Whisstock, Michelle L Halls, Andrew M Ellisdon.
      Neurofibromin (NF1) mutations cause neurofibromatosis type 1 and drive numerous cancers, including breast and brain tumors. NF1 inhibits cellular proliferation through its guanosine triphosphatase-activating protein (GAP) activity against rat sarcoma (RAS). In the present study, cryo-electron microscope studies reveal that the human ~640-kDa NF1 homodimer features a gigantic 30 × 10 nm array of α-helices that form a core lemniscate-shaped scaffold. Three-dimensional variability analysis captured the catalytic GAP-related domain and lipid-binding SEC-PH domains positioned against the core scaffold in a closed, autoinhibited conformation. We postulate that interaction with the plasma membrane may release the closed conformation to promote RAS inactivation. Our structural data further allow us to map the location of disease-associated NF1 variants and provide a long-sought-after structural explanation for the extreme susceptibility of the molecule to loss-of-function mutations. Collectively these findings present potential new routes for therapeutic modulation of the RAS pathway.
    DOI:  https://doi.org/10.1038/s41594-021-00687-2
  15. Nature. 2021 Dec 08.
    Structural basis of inhibition of the human SGLT2-MAP17 glucose transporter.
    Yange Niu, Rui Liu, Chengcheng Guan, Yuan Zhang, Zhixing Chen, Stefan Hoerer, Herbert Nar, Lei Chen.
      Human sodium-glucose cotransporter 2 (hSGLT2) mediates the reabsorption of the majority of filtrated glucose in the kidney1. Pharmacological inhibition of hSGLT2 by oral small-molecule inhibitors, such as empagliflozin, leads to enhanced excretion of glucose and is widely used in the clinic to manage blood glucose levels for the treatment of type 2 diabetes1. Here we determined the cryogenic electron microscopy structure of the hSGLT2-MAP17 complex in the empagliflozin-bound state to an overall resolution of 2.95 Å. Our structure shows eukaryotic SGLT-specific structural features. MAP17 interacts with transmembrane helix 13 of hSGLT2. Empagliflozin occupies both the sugar-substrate-binding site and the external vestibule to lock hSGLT2 in an outward-open conformation, thus inhibiting the transport cycle. Our work provides a framework for understanding the mechanism of SLC5A family glucose transporters and also develops a foundation for the future rational design and optimization of new inhibitors targeting these transporters.
    DOI:  https://doi.org/10.1038/s41586-021-04212-9
  16. Nature. 2021 Dec 08.
    Structure of pathological TDP-43 filaments from ALS with FTLD.
    Diana Arseni, Masato Hasegawa, Alexey G Murzin, Fuyuki Kametani, Makoto Arai, Mari Yoshida, Benjamin Ryskeldi-Falcon.
      The abnormal aggregation of TAR DNA-binding protein 43 kDa (TDP-43) in neurons and glia is the defining pathological hallmark of the neurodegenerative disease amyotrophic lateral sclerosis (ALS) and multiple forms of frontotemporal lobar degeneration (FTLD)1,2. It is also common in other diseases, including Alzheimer's and Parkinson's. No disease-modifying therapies exist for these conditions and early diagnosis is not possible. The structures of pathological TDP-43 aggregates are unknown. Here we used cryo-electron microscopy to determine the structures of aggregated TDP-43 in the frontal and motor cortices of an individual who had ALS with FTLD and from the frontal cortex of a second individual with the same diagnosis. An identical amyloid-like filament structure comprising a single protofilament was found in both brain regions and individuals. The ordered filament core spans residues 282-360 in the TDP-43 low-complexity domain and adopts a previously undescribed double-spiral-shaped fold, which shows no similarity to those of TDP-43 filaments formed in vitro3,4. An abundance of glycine and neutral polar residues facilitates numerous turns and restricts β-strand length, which results in an absence of β-sheet stacking that is associated with cross-β amyloid structure. An uneven distribution of residues gives rise to structurally and chemically distinct surfaces that face external densities and suggest possible ligand-binding sites. This work enhances our understanding of the molecular pathogenesis of ALS and FTLD and informs the development of diagnostic and therapeutic agents that target aggregated TDP-43.
    DOI:  https://doi.org/10.1038/s41586-021-04199-3
  17. Nature. 2021 Dec 08.
    Structure and mechanism of the SGLT family of glucose transporters.
    Lei Han, Qianhui Qu, Deniz Aydin, Ouliana Panova, Michael J Robertson, Yan Xu, Ron O Dror, Georgios Skiniotis, Liang Feng.
      Glucose is a primary energy source in living cells. The discovery in 1960s that a sodium gradient powers the active uptake of glucose in the intestine1 heralded the concept of a secondary active transporter that can catalyse the movement of a substrate against an electrochemical gradient by harnessing energy from another coupled substrate. Subsequently, coupled Na+/glucose transport was found to be mediated by sodium-glucose cotransporters2,3 (SGLTs). SGLTs are responsible for active glucose and galactose absorption in the intestine and for glucose reabsorption in the kidney4, and are targeted by multiple drugs to treat diabetes5. Several members within the SGLT family transport key metabolites other than glucose2. Here we report cryo-electron microscopy structures of the prototypic human SGLT1 and a related monocarboxylate transporter SMCT1 from the same family. The structures, together with molecular dynamics simulations and functional studies, define the architecture of SGLTs, uncover the mechanism of substrate binding and selectivity, and shed light on water permeability of SGLT1. These results provide insights into the multifaceted functions of SGLTs.
    DOI:  https://doi.org/10.1038/s41586-021-04211-w
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