Krios I-Titan Krios I at Diamond
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Diamond Proposal Number(s):
[17434]
Abstract: AMPA receptors (AMPARs) mediate the majority of excitatory transmission in the brain and enable the synaptic plasticity that underlies learning1. A diverse array of AMPAR signalling complexes are established by receptor auxiliary subunits, which associate with the AMPAR in various combinations to modulate trafficking, gating and synaptic strength2. However, their mechanisms of action are poorly understood. Here we determine cryo-electron microscopy structures of the heteromeric GluA1–GluA2 receptor assembled with both TARP-γ8 and CNIH2, the predominant AMPAR complex in the forebrain, in both resting and active states. Two TARP-γ8 and two CNIH2 subunits insert at distinct sites beneath the ligand-binding domains of the receptor, with site-specific lipids shaping each interaction and affecting the gating regulation of the AMPARs. Activation of the receptor leads to asymmetry between GluA1 and GluA2 along the ion conduction path and an outward expansion of the channel triggers counter-rotations of both auxiliary subunit pairs, promoting the active-state conformation. In addition, both TARP-γ8 and CNIH2 pivot towards the pore exit upon activation, extending their reach for cytoplasmic receptor elements. CNIH2 achieves this through its uniquely extended M2 helix, which has transformed this endoplasmic reticulum-export factor into a powerful AMPAR modulator that is capable of providing hippocampal pyramidal neurons with their integrative synaptic properties.
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Jun 2021
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Krios II-Titan Krios II at Diamond
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Melisa
Lazaro
,
Roberto
Melero
,
Charlotte
Huet
,
Jorge
Lopez-Alonso
,
Sandra
Delgado
,
Alexandra
Dodu
,
Eduardo M.
Bruch
,
Luciano A.
Abriata
,
Pedro M.
Alzari
,
Mikel
Valle
,
María-Natalia
Lisa
Diamond Proposal Number(s):
[14743]
Open Access
Abstract: Glutamate dehydrogenases (GDHs) are widespread metabolic enzymes that play key roles in nitrogen homeostasis. Large glutamate dehydrogenases composed of 180 kDa subunits (L-GDHs180) contain long N- and C-terminal segments flanking the catalytic core. Despite the relevance of L-GDHs180 in bacterial physiology, the lack of structural data for these enzymes has limited the progress of functional studies. Here we show that the mycobacterial L-GDH180 (mL-GDH180) adopts a quaternary structure that is radically different from that of related low molecular weight enzymes. Intersubunit contacts in mL-GDH180 involve a C-terminal domain that we propose as a new fold and a flexible N-terminal segment comprising ACT-like and PAS-type domains that could act as metabolic sensors for allosteric regulation. These findings uncover unique aspects of the structure-function relationship in the subfamily of L-GDHs.
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Jun 2021
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Krios I-Titan Krios I at Diamond
Krios II-Titan Krios II at Diamond
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Andreas
Schedlbauer
,
Idoia
Iturrioz
,
Borja
Ochoa-Lizarralde
,
Tammo
Diercks
,
Jorge Pedro
Lopez-Alonso
,
José Luis
Lavin
,
Tatsuya
Kaminishi
,
Retina
Çapuni
,
Neha
Dhimole
,
Elisa
De Astigarraga
,
David
Gil-Carton
,
Paola
Fucini
,
Sean R.
Connell
Diamond Proposal Number(s):
[17171, 15422]
Open Access
Abstract: While a structural description of the molecular mechanisms guiding ribosome assembly in eukaryotic systems is emerging, bacteria use an unrelated core set of assembly factors for which high-resolution structural information is still missing. To address this, we used single-particle cryo–electron microscopy to visualize the effects of bacterial ribosome assembly factors RimP, RbfA, RsmA, and RsgA on the conformational landscape of the 30S ribosomal subunit and obtained eight snapshots representing late steps in the folding of the decoding center. Analysis of these structures identifies a conserved secondary structure switch in the 16S ribosomal RNA central to decoding site maturation and suggests both a sequential order of action and molecular mechanisms for the assembly factors in coordinating and controlling this switch. Structural and mechanistic parallels between bacterial and eukaryotic systems indicate common folding features inherent to all ribosomes.
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Jun 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 GTPase Rab1 is a master regulator of the early secretory pathway and is critical for autophagy. Rab1 activation is controlled by its guanine nucleotide exchange factor, the multisubunit TRAPPIII complex. Here, we report the 3.7 Å cryo-EM structure of the Saccharomyces cerevisiae TRAPPIII complex bound to its substrate Rab1/Ypt1. The structure reveals the binding site for the Rab1/Ypt1 hypervariable domain, leading to a model for how the complex interacts with membranes during the activation reaction. We determined that stable membrane binding by the TRAPPIII complex is required for robust activation of Rab1/Ypt1 in vitro and in vivo, and is mediated by a conserved amphipathic α-helix within the regulatory Trs85 subunit. Our results show that the Trs85 subunit serves as a membrane anchor, via its amphipathic helix, for the entire TRAPPIII complex. These findings provide a structural understanding of Rab activation on organelle and vesicle membranes.
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May 2021
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Krios I-Titan Krios I at Diamond
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Open Access
Abstract: The regulation of the genome is an essential biological task. In eukaryotes, fundamental nuclear processes such as DNA replication, transcription and repair require a large variety of protein effectors to ensure the correct transmission of genetic information, for regulated gene expression and to maintain genome integrity. The phosphatidylinositol 3-kinase-related kinase (PIKK) protein family represents a group of very large and highly conserved Ser/Thr-protein kinases, where most function in genome regulation processes. S. cerevisiae proteins Tra1 and Mec1 (known as TRRAP and ATR in humans) are two essential PIKKs found in the nucleus. Tra1 is a 3,744-residue protein and a shared subunit between the chromatin modifying complexes SAGA and NuA4. Tra1 stimulates transcriptional activation by directly interacting with transcription activators and is also involved in DNA repair. Here, I present the near-atomic resolution cryo-EM structure of the full-length Tra1 polypeptide. A “de novo” atomic model was built from the map, revealing the unique arrangement of Tra1 alpha-solenoid, which is organised into an N-terminal Finger segment inserted into a circular Cradle region before the Kinase domain. Structural interpretation of previously published Tra1 mutants allowed to identify a Gal4 binding region. Mec1 is a 2,368-residue protein that forms a complex with Ddc2 (ATRIP in humans), and participates in the DNA-Damage-Response, Replication-Stress-Response, in telomere maintenance and meiosis, and its kinase activity influences cell cycle progression. Here, I present the high-resolution cryo-EM structure of the heterodimeric Mec1-Ddc2 complex, providing the first complete atomic model of Mec1. The structure reveals how the complex is assembled, showing extensive interactions between Ddc2 solenoid region and Mec1. The map also shows the integration point of Ddc2 N-terminal region into the complex, and together with existing structural data for the interaction of Ddc2 coiled-coil with RPA, an integrative model shed light in the understanding of Mec1 recruitment to RPA-coated ssDNA.
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May 2021
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Krios I-Titan Krios I at Diamond
Krios II-Titan Krios II at Diamond
Krios III-Titan Krios III at Diamond
Krios IV-Titan Krios IV at Diamond
Talos-Talos Arctica at Diamond
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Diamond Proposal Number(s):
[23047]
Open Access
Abstract: Cryo-electron microscopy (cryoEM) is a powerful technique for structure determination of macromolecular complexes, via single particle analysis (SPA). The overall process involves i) vitrifying the specimen in a thin film supported on a cryoEM grid; ii) screening the specimen to assess particle distribution and ice quality; iii) if the grid is suitable, collecting a single particle dataset for analysis; and iv) image processing to yield an EM density map. In this protocol, an overview for each of these steps is provided, with a focus on the variables which a user can modify during the workflow and the troubleshooting of common issues. With remote microscope operation becoming standard in many facilities, variations on imaging protocols to assist users in efficient operation and imaging when physical access to the microscope is limited will be described.
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May 2021
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Krios II-Titan Krios II at Diamond
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Yasunori
Watanabe
,
Luiza
Mendonca
,
Elizabeth R.
Allen
,
Andrew
Howe
,
Mercede
Lee
,
Joel D.
Allen
,
Himanshi
Chawla
,
David
Pulido
,
Francesca
Donnellan
,
Hannah
Davies
,
Marta
Ulaszewska
,
Sandra
Belij-Rammerstorfer
,
Susan
Morris
,
Anna-Sophia
Krebs
,
Wanwisa
Dejnirattisai
,
Juthathip
Mongkolsapaya
,
Piyada
Supasa
,
Gavin R.
Screaton
,
Catherine M.
Green
,
Teresa
Lambe
,
Peijun
Zhang
,
Sarah C.
Gilbert
,
Max
Crispin
Diamond Proposal Number(s):
[18477, 21005, 21004]
Abstract: Vaccine development against the SARS-CoV-2 virus focuses on the principal target of the neutralizing immune response, the spike (S) glycoprotein. Adenovirus-vectored vaccines offer an effective platform for the delivery of viral antigen, but it is important for the generation of neutralizing antibodies that they produce appropriately processed and assembled viral antigen that mimics that observed on the SARS-CoV-2 virus. Here, we describe the structure, conformation, and glycosylation of the S protein derived from the adenovirus-vectored ChAdOx1 nCoV-19/AZD1222 vaccine. We demonstrate native-like post-translational processing and assembly, and reveal the expression of S proteins on the surface of cells adopting the trimeric prefusion conformation. The data presented here confirm the use of ChAdOx1 adenovirus vectors as a leading platform technology for SARS-CoV-2 vaccines.
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Apr 2021
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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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Matthew D.
Figley
,
Weixi
Gu
,
Jeffrey D.
Nanson
,
Yun
Shi
,
Yo
Sasaki
,
Katie
Cunnea
,
Alpeshkumar K.
Malde
,
Xinying
Jia
,
Zhenyao
Luo
,
Forhad K.
Saikot
,
Tamim
Mosaiab
,
Veronika
Masic
,
Stephanie
Holt
,
Lauren
Hartley-Tassell
,
Helen Y.
Mcguinness
,
Mohammad K.
Manik
,
Todd
Bosanac
,
Michael J.
Landsberg
,
Philip S.
Kerry
,
Mehdi
Mobli
,
Robert O.
Hughes
,
Jeffrey
Milbrandt
,
Bostjan
Kobe
,
Aaron
Diantonio
,
Thomas
Ve
Diamond Proposal Number(s):
[24981]
Abstract: Axon degeneration is a central pathological feature of many neurodegenerative diseases. Sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1) is a nicotinamide adenine dinucleotide (NAD+)-cleaving enzyme whose activation triggers axon destruction. Loss of the biosynthetic enzyme NMNAT2, which converts nicotinamide mononucleotide (NMN) to NAD+, activates SARM1 via an unknown mechanism. Using structural, biochemical, biophysical, and cellular assays, we demonstrate that SARM1 is activated by an increase in the ratio of NMN to NAD+ and show that both metabolites compete for binding to the auto-inhibitory N-terminal armadillo repeat (ARM) domain of SARM1. We report structures of the SARM1 ARM domain bound to NMN and of the homo-octameric SARM1 complex in the absence of ligands. We show that NMN influences the structure of SARM1 and demonstrate via mutagenesis that NMN binding is required for injury-induced SARM1 activation and axon destruction. Hence, SARM1 is a metabolic sensor responding to an increased NMN/NAD+ ratio by cleaving residual NAD+, thereby inducing feedforward metabolic catastrophe and axonal demise.
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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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