Krios I-Titan Krios I at Diamond
Krios II-Titan Krios II at Diamond
Krios III-Titan Krios III at Diamond
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Luiza
Mendonca
,
Dapeng
Sun
,
Jiying
Ning
,
Jiwei
Liu
,
Abhay
Kotecha
,
Mateusz
Olek
,
Thomas
Frosio
,
Xiaofeng
Fu
,
Benjamin A.
Himes
,
Alex B.
Kleinpeter
,
Eric O.
Freed
,
Jing
Zhou
,
Christopher
Aiken
,
Peijun
Zhang
Diamond Proposal Number(s):
[18477, 21005, 21004]
Open Access
Abstract: Gag is the HIV structural precursor protein which is cleaved by viral protease to produce mature infectious viruses. Gag is a polyprotein composed of MA (matrix), CA (capsid), SP1, NC (nucleocapsid), SP2 and p6 domains. SP1, together with the last eight residues of CA, have been hypothesized to form a six-helix bundle responsible for the higher-order multimerization of Gag necessary for HIV particle assembly. However, the structure of the complete six-helix bundle has been elusive. Here, we determined the structures of both Gag in vitro assemblies and Gag viral-like particles (VLPs) to 4.2 Å and 4.5 Å resolutions using cryo-electron tomography and subtomogram averaging by emClarity. A single amino acid mutation (T8I) in SP1 stabilizes the six-helix bundle, allowing to discern the entire CA-SP1 helix connecting to the NC domain. These structures provide a blueprint for future development of small molecule inhibitors that can lock SP1 in a stable helical conformation, interfere with virus maturation, and thus block HIV-1 infection.
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Apr 2021
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Krios I-Titan Krios I at Diamond
Krios II-Titan Krios II at Diamond
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Open Access
Abstract: The ATPase Prp16 governs equilibrium between the branching (B∗/C) and exon ligation (C∗/P) conformations of the spliceosome. Here, we present the electron cryomicroscopy reconstruction of the Saccharomyces cerevisiae C-complex spliceosome at 2.8 Å resolution and identify a novel C-complex intermediate (Ci) that elucidates the molecular basis for this equilibrium. The exon-ligation factors Prp18 and Slu7 bind to Ci before ATP hydrolysis by Prp16 can destabilize the branching conformation. Biochemical assays suggest that these pre-bound factors prime the C complex for conversion to C∗ by Prp16. A complete model of the Prp19 complex (NTC) reveals how the branching factors Yju2 and Isy1 are recruited by the NTC before branching. Prp16 remodels Yju2 binding after branching, allowing Yju2 to remain tethered to the NTC in the C∗ complex to promote exon ligation. Our results explain how Prp16 action modulates the dynamic binding of step-specific factors to alternatively stabilize the C or C∗ conformation and establish equilibrium of the catalytic spliceosome.
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Mar 2021
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Krios I-Titan Krios I at Diamond
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Yang
Shi
,
Alexey G.
Murzin
,
Benjamin
Falcon
,
Alexander
Epstein
,
Jonathan
Machin
,
Paul
Tempest
,
Kathy L.
Newell
,
Ruben
Vidal
,
Holly J.
Garringer
,
Naruhiko
Sahara
,
Makoto
Higuchi
,
Bernardino
Ghetti
,
Ming-Kuei
Jang
,
Sjors H. W.
Scheres
,
Michel
Goedert
Diamond Proposal Number(s):
[17434]
Open Access
Abstract: Tau and Aβ assemblies of Alzheimer’s disease (AD) can be visualized in living subjects using positron emission tomography (PET). Tau assemblies comprise paired helical and straight filaments (PHFs and SFs). APN-1607 (PM-PBB3) is a recently described PET ligand for AD and other tau proteinopathies. Since it is not known where in the tau folds PET ligands bind, we used electron cryo-microscopy (cryo-EM) to determine the binding sites of APN-1607 in the Alzheimer fold. We identified two major sites in the β-helix of PHFs and SFs and a third major site in the C-shaped cavity of SFs. In addition, we report that tau filaments from posterior cortical atrophy (PCA) and primary age-related tauopathy (PART) are identical to those from AD. In support, fluorescence labelling showed binding of APN-1607 to intraneuronal inclusions in AD, PART and PCA. Knowledge of the binding modes of APN-1607 to tau filaments may lead to the development of new ligands with increased specificity and binding activity. We show that cryo-EM can be used to identify the binding sites of small molecules in amyloid filaments.
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Mar 2021
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Krios I-Titan Krios I at Diamond
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Open Access
Abstract: The biogenic formation of hemozoin crystals, a crucial process in heme detoxification by the malaria parasite, is reviewed as an antimalarial drug target. We first focus on the in‐vivo formation of hemozoin. A model is presented, based on native‐contrast 3D imaging obtained by X‐ray and electron microscopy, that hemozoin nucleates at the inner membrane leaflet of the parasitic digestive vacuole, and grows in the adjacent aqueous medium. Having observed quantities of hemoglobin and hemozoin in the digestive vacuole, we present a model that heme liberation from hemoglobin and hemozoin formation is an assembly‐line process. The crystallization is preceded by reaction between heme monomers yielding hematin dimers involving fewer types of isomers than in synthetic hemozoin; this is indicative of protein‐induced dimerization. Models of antimalarial drugs binding onto hemozoin surfaces are reviewed. This is followed by a description of bromoquine, a chloroquine drug analogue, capping a significant fraction of hemozoin surfaces within the digestive vacuole and accumulation of the drug, presumably a bromoquine–hematin complex, at the vacuole's membrane.
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Mar 2021
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Krios I-Titan Krios I at Diamond
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Open Access
Abstract: Chemotactic responses in motile bacteria are the result of sophisticated signal transduction by large, highly organized arrays of sensory proteins. Despite tremendous progress in the understanding of chemosensory array structure and function, a structural basis for the heightened sensitivity of networked chemoreceptors is not yet complete. Here, we present cryo-electron tomography visualisations of native-state chemosensory arrays in E. coli minicells. Strikingly, these arrays appear to exhibit a p2-symmetric array architecture that differs markedly from the p6-symmetric architecture previously described in E. coli. Based on this data, we propose molecular models of this alternative architecture and the canonical p6-symmetric assembly. We evaluate our observations and each model in the context of previously published data, assessing the functional implications of an alternative architecture and effects for future studies.
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Mar 2021
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Krios I-Titan Krios I at Diamond
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Stanislau
Yatskevich
,
Jessie S.
Kroonen
,
Claudio
Alfieri
,
Thomas
Tischer
,
Anna C.
Howes
,
Linda
Clijsters
,
Jing
Yang
,
Ziguo
Zhang
,
Kaige
Yan
,
Alfred C. O.
Vertegaal
,
David
Barford
Diamond Proposal Number(s):
[13708]
Open Access
Abstract: The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that controls cell cycle transitions. Its regulation by the spindle assembly checkpoint (SAC) is coordinated with the attachment of sister chromatids to the mitotic spindle. APC/C SUMOylation on APC4 ensures timely anaphase onset and chromosome segregation. To understand the structural and functional consequences of APC/C SUMOylation, we reconstituted SUMOylated APC/C for electron cryo-microscopy and biochemical analyses. SUMOylation of the APC/C causes a substantial rearrangement of the WHB domain of APC/C’s cullin subunit (APC2WHB). Although APC/CCdc20 SUMOylation results in a modest impact on normal APC/CCdc20 activity, repositioning APC2WHB reduces the affinity of APC/CCdc20 for the mitotic checkpoint complex (MCC), the effector of the SAC. This attenuates MCC-mediated suppression of APC/CCdc20 activity, allowing for more efficient ubiquitination of APC/CCdc20 substrates in the presence of the MCC. Thus, SUMOylation stimulates the reactivation of APC/CCdc20 when the SAC is silenced, contributing to timely anaphase onset.
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Mar 2021
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Krios I-Titan Krios I at Diamond
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Diamond Proposal Number(s):
[19823]
Abstract: Mitochondrial ribosomes (mitoribosomes) are tethered to the mitochondrial inner membrane to facilitate the cotranslational membrane insertion of the synthesized proteins. We report cryo–electron microscopy structures of human mitoribosomes with nascent polypeptide, bound to the insertase oxidase assembly 1–like (OXA1L) through three distinct contact sites. OXA1L binding is correlated with a series of conformational changes in the mitoribosomal large subunit that catalyze the delivery of newly synthesized polypeptides. The mechanism relies on the folding of mL45 inside the exit tunnel, forming two specific constriction sites that would limit helix formation of the nascent chain. A gap is formed between the exit and the membrane, making the newly synthesized proteins accessible. Our data elucidate the basis by which mitoribosomes interact with the OXA1L insertase to couple protein synthesis and membrane delivery.
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Feb 2021
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I03-Macromolecular Crystallography
Krios I-Titan Krios I at Diamond
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Wanwisa
Dejnirattisai
,
Daming
Zhou
,
Helen M.
Ginn
,
Helen M. E.
Duyvesteyn
,
Piyada
Supasa
,
James Brett
Case
,
Yuguang
Zhao
,
Thomas
Walter
,
Alexander J.
Mentzer
,
Chang
Liu
,
Beibei
Wang
,
Guido C.
Paesen
,
Jose
Slon-Campos
,
César
López-Camacho
,
Natasha M.
Kafai
,
Adam L.
Bailey
,
Rita E.
Chen
,
Baoling
Ying
,
Craig
Thompson
,
Jai
Bolton
,
Alex
Fyfe
,
Sunetra
Gupta
,
Tiong Kit
Tan
,
Javier
Gilbert-Jaramillo
,
William
James
,
Michael
Knight
,
Miles W.
Carroll
,
Donal
Skelly
,
Christina
Dold
,
Yanchun
Peng
,
Robert
Levin
,
Tao
Dong
,
Andrew J.
Pollard
,
Julian C.
Knight
,
Paul
Klenerman
,
Nigel
Temperton
,
David R.
Hall
,
Mark A.
Williams
,
Neil G.
Paterson
,
Felicity
Bertram
,
C. Alistair
Siebert
,
Daniel K.
Clare
,
Andrew
Howe
,
Julika
Radecke
,
Yun
Song
,
Alain R.
Townsend
,
Kuan-Ying A.
Huang
,
Elizabeth E.
Fry
,
Juthathip
Mongkolsapaya
,
Michael S.
Diamond
,
Jingshan
Ren
,
David I.
Stuart
,
Gavin R.
Screaton
Diamond Proposal Number(s):
[27009, 26983]
Open Access
Abstract: Antibodies are crucial to immune protection against SARS-CoV-2, with some in emergency use as therapeutics. Here we identify 377 human monoclonal antibodies (mAbs) recognizing the virus spike, and focus mainly on 80 that bind the receptor binding domain (RBD). We devise a competition data driven method to map RBD binding sites. We find that although antibody binding sites are widely dispersed, neutralizing antibody binding is focused, with nearly all highly inhibitory mAbs (IC50<0.1μg/ml) blocking receptor interaction, except for one that binds a unique epitope in the N-terminal domain. Many of these neutralizing mAbs use public V-genes and are close to germline. We dissect the structural basis of recognition for this large panel of antibodies through X-ray crystallography and cryo-electron microscopy of 19 Fab-antigen structures. We find novel binding modes for some potently inhibitory antibodies and demonstrate that strongly neutralizing mAbs protect, prophylactically or therapeutically, in animal models.
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Feb 2021
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Krios I-Titan Krios I at Diamond
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Diamond Proposal Number(s):
[14769]
Open Access
Abstract: The Tuberous Sclerosis Complex (TSC) protein complex (TSCC), comprising TSC1, TSC2, and TBC1D7, is widely recognised as a key integration hub for cell growth and intracellular stress signals upstream of the mammalian target of rapamycin complex 1 (mTORC1). The TSCC negatively regulates mTORC1 by acting as a GTPase-activating protein (GAP) towards the small GTPase Rheb. Both human TSC1 and TSC2 are important tumour suppressors, and mutations in them underlie the disease tuberous sclerosis.
We used single-particle cryo-EM to reveal the organisation and architecture of the complete human TSCC. We show that TSCC forms an elongated scorpion-like structure, consisting of a central “body”, with a “pincer” and a “tail” at the respective ends. The “body” is composed of a flexible TSC2 HEAT repeat dimer, along the surface of which runs the TSC1 coiled-coil backbone, breaking the symmetry of the dimer. Each end of the body is structurally distinct, representing the N- and C-termini of TSC1; a “pincer” is formed by the highly flexible N-terminal TSC1 core domains and a barbed “tail” makes up the TSC1 coiled-coil-TBC1D7 junction. The TSC2 GAP domain is found abutting the centre of the body on each side of the dimerisation interface, poised to bind a pair of Rheb molecules at a similar separation to the pair in activated mTORC1.
Our architectural dissection reveals the mode of association and topology of the complex, casts light on the recruitment of Rheb to the TSCC, and also hints at functional higher order oligomerisation, which has previously been predicted to be important for Rheb-signalling suppression.
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Jan 2021
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Krios I-Titan Krios I at Diamond
Krios III-Titan Krios III at Diamond
Krios V-Titan Krios V at Diamond
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Diamond Proposal Number(s):
[18659]
Open Access
Abstract: Cholesterol-dependent cytolysins (CDCs) are pore-forming proteins that serve as major virulence factors for pathogenic bacteria. They target eukaryotic cells using different mechanisms, but all require the presence of cholesterol to pierce lipid bilayers. How CDCs use cholesterol to selectively lyse cells is essential for understanding virulence strategies of several pathogenic bacteria, and for repurposing CDCs to kill new cellular targets. Here we address that question by trapping an early state of pore formation for the CDC intermedilysin, bound to the human immune receptor CD59 in a nanodisc model membrane. Our cryo electron microscopy map reveals structural transitions required for oligomerization, which include the lateral movement of a key amphipathic helix. We demonstrate that the charge of this helix is crucial for tuning lytic activity of CDCs. Furthermore, we discover modifications that overcome the requirement of cholesterol for membrane rupture, which may facilitate engineering the target-cell specificity of pore-forming proteins.
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Nov 2020
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