Krios III-Titan Krios III at Diamond
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Manuel
Schweighauser
,
Diana
Arseni
,
Mehtap
Bacioglu
,
Melissa
Huang
,
Sofia
Lovestam
,
Yang
Shi
,
Yang
Yang
,
Wenjuan
Zhang
,
Abhay
Kotecha
,
Holly J.
Garringer
,
Ruben
Vidal
,
Grace I.
Hallin
,
Kathy L.
Newell
,
Airi
Tarutani
,
Shigeo
Murayama
,
Masayuki
Miyazaki
,
Yuko
Saito
,
Mari
Yoshida
,
Kazuko
Hasegawa
,
Tammaryn
Lashley
,
Tamas
Revesz
,
Gabor G.
Kovacs
,
John
Van Swieten
,
Masaki
Takao
,
Masato
Hasegawa
,
Bernardino
Ghetti
,
Maria Grazia
Spillantini
,
Benjamin
Ryskeldi-Falcon
,
Alexey G.
Murzin
,
Michel
Goedert
,
Sjors H. W.
Scheres
Diamond Proposal Number(s):
[17434, 23268]
Abstract: Many age-dependent neurodegenerative diseases, like Alzheimer’s and Parkinson’s, are characterised by abundant inclusions of amyloid filaments. Filamentous inclusions of the proteins tau, amyloid-β (Aβ), α-synuclein and TDP-43 are the most common1,2. Here, we used electron cryo-microscopy (cryo-EM) structure determination to show that residues 120-254 of the lysosomal type II transmembrane protein 106B (TMEM106B) also form amyloid filaments in human brains. We determined the cryo-EM structures of TMEM106B filaments from a number of brain regions of 22 individuals with abundant amyloid deposits, including sporadic and inherited tauopathies, Aβ-amyloidoses, synucleinopathies and TDP-43 proteinopathies, as well as from the frontal cortex of 3 neurologically normal individuals with no or only few amyloid deposits. We observed three TMEM106B folds, with no clear relationships between folds and diseases. TMEM106B filaments correlated with the presence of a 29 kDa sarkosyl-insoluble fragment and globular cytoplasmic inclusions, as detected by an antibody specific for the C-terminal region of TMEM106B. The identification of TMEM106B filaments in the brains of older, but not younger, neurologically normal individuals indicates that they form in an age-dependent manner.
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Mar 2022
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Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[23268]
Open Access
Abstract: AMPA-type glutamate receptors (AMPARs) mediate rapid signal transmission at excitatory synapses in the brain. Glutamate binding to the receptor’s ligand-binding domains (LBDs) leads to ion channel activation and desensitization. Gating kinetics shape synaptic transmission and are strongly modulated by transmembrane AMPAR regulatory proteins (TARPs) through currently incompletely resolved mechanisms. Here, electron cryo-microscopy structures of the GluA1/2 TARP-γ8 complex, in both open and desensitized states (at 3.5 Å), reveal state-selective engagement of the LBDs by the large TARP-γ8 loop (‘β1’), elucidating how this TARP stabilizes specific gating states. We further show how TARPs alter channel rectification, by interacting with the pore helix of the selectivity filter. Lastly, we reveal that the Q/R-editing site couples the channel constriction at the filter entrance to the gate, and forms the major cation binding site in the conduction path. Our results provide a mechanistic framework of how TARPs modulate AMPAR gating and conductance.
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Feb 2022
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I04-Macromolecular Crystallography
I23-Long wavelength MX
I24-Microfocus Macromolecular Crystallography
Krios III-Titan Krios III at Diamond
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Paola
Lanzoni-Mangutchi
,
Oishik
Banerji
,
Jason
Wilson
,
Anna
Barwinska-Sendra
,
Joseph A.
Kirk
,
Filipa
Vaz
,
Shauna
O’beirne
,
Arnaud
Basle
,
Kamel
El Omari
,
Armin
Wagner
,
Neil F.
Fairweather
,
Gillian R.
Douce
,
Per A.
Bullough
,
Robert P.
Fagan
,
Paula
Salgado
Diamond Proposal Number(s):
[15523, 18598, 19832]
Open Access
Abstract: Many bacteria and archaea possess a two-dimensional protein array, or S-layer, that covers the cell surface and plays crucial roles in cell physiology. Here, we report the crystal structure of SlpA, the main S-layer protein of the bacterial pathogen Clostridioides difficile, and use electron microscopy to study S-layer organisation and assembly. The SlpA crystal lattice mimics S-layer assembly in the cell, through tiling of triangular prisms above the cell wall, interlocked by distinct ridges facing the environment. Strikingly, the array is very compact, with pores of only ~10 Å in diameter, compared to other S-layers (30–100 Å). The surface-exposed flexible ridges are partially dispensable for overall structure and assembly, although a mutant lacking this region becomes susceptible to lysozyme, an important molecule in host defence. Thus, our work gives insights into S-layer organisation and provides a basis for development of C. difficile-specific therapeutics.
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Feb 2022
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Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[18074]
Open Access
Abstract: Mitochondrial complex I (NADH:ubiquinone oxidoreductase), a crucial enzyme in energy metabolism, captures the redox potential energy from NADH oxidation and ubiquinone reduction to create the proton motive force used to drive ATP synthesis in oxidative phosphorylation. Recent high-resolution cryo-EM analyses have provided detailed structural knowledge of the catalytic machinery of complex I, but not of the molecular principles of its energy transduction mechanism. Although ubiquinone is considered to bind in a long channel at the interface of the membrane-embedded and hydrophilic domains, and channel residues are likely involved in coupling substrate reduction to proton translocation, no structures with the channel fully occupied have yet been described. Here, we report the cryo-EM structure of mouse complex I with an extremely tight-binding natural-product acetogenin inhibitor, which resembles the native substrate, bound along the full length of the expected ubiquinone-binding channel. Our structure reveals the mode of acetogenin binding and the molecular basis for structure–activity relationships within the acetogenin family. It also shows that acetogenins are such potent inhibitors because they are highly hydrophobic molecules that contain two specific hydrophilic moieties ideally spaced to lock into two hydrophilic regions of the otherwise hydrophobic channel. The central hydrophilic section of the channel does not favor binding of the isoprenoid chain when the native substrate is fully bound, but stabilises the ubiquinone/ubiquinol headgroup as it transits to/from the active site. Therefore, the amphipathic nature of the channel supports both tight binding of the amphipathic inhibitor and rapid exchange of the ubiquinone/ubiquinol substrate and product.
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Jan 2022
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Krios III-Titan Krios III at Diamond
Krios IV-Titan Krios IV at Diamond
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Diamond Proposal Number(s):
[17057]
Open Access
Abstract: The structure has been determined by electron cryomicroscopy of the adenosine triphosphate (ATP) synthase from Mycobacterium smegmatis. This analysis confirms features in a prior description of the structure of the enzyme, but it also describes other highly significant attributes not recognized before that are crucial for understanding the mechanism and regulation of the mycobacterial enzyme. First, we resolved not only the three main states in the catalytic cycle described before but also eight substates that portray structural and mechanistic changes occurring during a 360° catalytic cycle. Second, a mechanism of auto-inhibition of ATP hydrolysis involves not only the engagement of the C-terminal region of an α-subunit in a loop in the γ-subunit, as proposed before, but also a “fail-safe” mechanism involving the b′-subunit in the peripheral stalk that enhances engagement. A third unreported characteristic is that the fused bδ-subunit contains a duplicated domain in its N-terminal region where the two copies of the domain participate in similar modes of attachment of the two of three N-terminal regions of the α-subunits. The auto-inhibitory plus the associated “fail-safe” mechanisms and the modes of attachment of the α-subunits provide targets for development of innovative antitubercular drugs. The structure also provides support for an observation made in the bovine ATP synthase that the transmembrane proton-motive force that provides the energy to drive the rotary mechanism is delivered directly and tangentially to the rotor via a Grotthuss water chain in a polar L-shaped tunnel.
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Nov 2021
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Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[19832]
Open Access
Abstract: The O-linked β-N-acetylglucosamine modification is a core signalling mechanism, with erroneous patterns leading to cancer and neurodegeneration. Although thousands of proteins are subject to this modification, only a single essential glycosyltransferase catalyses its installation, the O-GlcNAc transferase, OGT. Previous studies have provided truncated structures of OGT through X-ray crystallography, but the full-length protein has never been observed. Here, we report a 5.3 Å cryo-EM model of OGT. We show OGT is a dimer, providing a structural basis for how some X-linked intellectual disability mutations at the interface may contribute to disease. We observe that the catalytic section of OGT abuts a 13.5 tetratricopeptide repeat unit region and find the relative positioning of these sections deviate from the previously proposed, X-ray crystallography-based model. We also note that OGT exhibits considerable heterogeneity in tetratricopeptide repeat units N-terminal to the dimer interface with repercussions for how OGT binds protein ligands and partners.
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Nov 2021
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Krios III-Titan Krios III at Diamond
Krios IV-Titan Krios IV at Diamond
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Diamond Proposal Number(s):
[20287]
Open Access
Abstract: RNA polymerase inhibition plays an important role in the regulation of transcription in response to environmental changes and in the virus-host relationship. Here we present the high-resolution structures of two such RNAP-inhibitor complexes that provide the structural bases underlying RNAP inhibition in archaea. The Acidianus two-tailed virus encodes the RIP factor that binds inside the DNA-binding channel of RNAP, inhibiting transcription by occlusion of binding sites for nucleic acid and the transcription initiation factor TFB. Infection with the Sulfolobus Turreted Icosahedral Virus induces the expression of the host factor TFS4, which binds in the RNAP funnel similarly to eukaryotic transcript cleavage factors. However, TFS4 allosterically induces a widening of the DNA-binding channel which disrupts trigger loop and bridge helix motifs. Importantly, the conformational changes induced by TFS4 are closely related to inactivated states of RNAP in other domains of life indicating a deep evolutionary conservation of allosteric RNAP inhibition.
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Sep 2021
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Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[21643]
Abstract: Photosystem I (PSI), found in all oxygenic photosynthetic organisms, uses solar energy to drive electron transport with nearly 100% quantum efficiency, thanks to fast energy transfer among antenna chlorophylls and charge separation in the reaction center. There is no complete consensus regarding the kinetics of the elementary steps involved in the overall trapping, especially the rate of primary charge separation. In this work, we employed two-dimensional coherent electronic spectroscopy to follow the dynamics of energy and electron transfer in a monomeric PSI complex from Synechocystis PCC 6803, containing only subunits A–E, K, and M, at 77 K. We also determined the structure of the complex to 4.3 Å resolution by cryoelectron microscopy with refinements to 2.5 Å. We applied structure-based modeling using a combined Redfield–Förster theory to compute the excitation dynamics. The absorptive 2D electronic spectra revealed fast excitonic/vibronic relaxation on time scales of 50–100 fs from the high-energy side of the absorption spectrum. Antenna excitations were funneled within 1 ps to a small pool of chlorophylls absorbing around 687 nm, thereafter decaying with 4–20 ps lifetimes, independently of excitation wavelength. Redfield–Förster energy transfer computations showed that the kinetics is limited by transfer from these red-shifted pigments. The rate of primary charge separation, upon direct excitation of the reaction center, was determined to be 1.2–1.5 ps–1. This result implies activationless electron transfer in PSI.
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Sep 2021
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Krios I-Titan Krios I at Diamond
Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[19865]
Abstract: Damage to DNA needs to be repaired quickly, or it can result in defects that eventually cause cancer and ageing, particularly when a cell is replicating. Fortunately, our cells have evolved sophisticated pathways to counter the damage. One key process in the cell is the ‘DNA damage response’, where signalling factors are recruited that coordinate cell cycle progression with DNA repair. In humans, ATR is a key protein involved in the start of the repair process. A team of scientists at Imperial College London and Washington University School of Medicine in St. Louis used high-resolution cryo-electron microscopy (cryo-EM) structures to identify how ATR kick-starts the DNA repair process.
ATR is sometimes mutated in cancer cells and is a validated drug target for cancer treatment. It and similar proteins are normally turned off (autoinhibited). They are activated when damage is detected. One key question is how ATR is maintained in an auto-inhibited state and how it is activated. The Mec1 yeast protein is essentially the same as human ATR. Using data collected at the Electron Bio-Imaging Centre (eBIC) at Diamond Light Source, the team obtained high-resolution structures of Mec1, in complex with its integral binding partner, Ddc2. In combination with biochemistry and genetics, these structures explain how this protein maintains an inhibited (off) state and the key steps required for its activation. These results allowed the researchers to propose a molecular mechanism for activation. This information helps to rationalise cancer mutations and provides a molecular framework for novel rational drug design of anticancer treatments.
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Jul 2021
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Krios III-Titan Krios III at Diamond
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Diamond Proposal Number(s):
[17434]
Open Access
Abstract: The TRAPP complexes are nucleotide exchange factors that play essential roles in membrane traffic and autophagy. TRAPPII activates Rab11, and TRAPPIII activates Rab1, with the two complexes sharing a core of small subunits that affect nucleotide exchange but being distinguished by specific large subunits that are essential for activity in vivo. Crystal structures of core subunits have revealed the mechanism of Rab activation, but how the core and the large subunits assemble to form the complexes is unknown. We report a cryo-EM structure of the entire Drosophila TRAPPIII complex. The TRAPPIII-specific subunits TRAPPC8 and TRAPPC11 hold the catalytic core like a pair of tongs, with TRAPPC12 and TRAPPC13 positioned at the joint between them. TRAPPC2 and TRAPPC2L link the core to the two large arms, with the interfaces containing residues affected by disease-causing mutations. The TRAPPC8 arm is positioned such that it would contact Rab1 that is bound to the core, indicating how the arm could determine the specificity of the complex. A lower resolution structure of TRAPPII shows a similar architecture and suggests that the TRAPP complexes evolved from a single ur-TRAPP.
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Jun 2021
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