B18-Core EXAFS
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Chunzhen
Yang
,
Gwenaëlle
Rousse
,
Katrine
Louise Svane
,
Paul E.
Pearce
,
Artem M.
Abakumov
,
Michael
Deschamps
,
Giannantonio
Cibin
,
Alan V.
Chadwick
,
Daniel Alves
Dalla Corte
,
Heine
Anton Hansen
,
Tejs
Vegge
,
Jean-marie
Tarascon
,
Alexis
Grimaud
Diamond Proposal Number(s):
[14239]
Open Access
Abstract: The production of hydrogen at a large scale by the environmentally-friendly electrolysis process is currently hampered by the slow kinetics of the oxygen evolution reaction (OER). We report a solid electrocatalyst α-Li2IrO3 which upon oxidation/delithiation chemically reacts with water to form a hydrated birnessite phase, the OER activity of which is five times greater than its non-reacted counterpart. This reaction enlists a bulk redox process during which hydrated potassium ions from the alkaline electrolyte are inserted into the structure while water is oxidized and oxygen evolved. This singular charge balance process for which the electrocatalyst is solid but the reaction is homogeneous in nature allows stabilizing the surface of the catalyst while ensuring stable OER performances, thus breaking the activity/stability tradeoff normally encountered for OER catalysts.
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Mar 2020
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Diamond Proposal Number(s):
[13775]
Abstract: The broad-spectrum antibiotic D-cycloserine (DCS) is a key component of regimens used to treat multi- and extensively drug-resistant tuberculosis. DCS, a structural analog of D-alanine, binds to and inactivates two essential enzymes involved in peptidoglycan biosynthesis, alanine racemase (Alr) and D-Ala:D-Ala ligase. Inactivation of Alr is thought to proceed via a mechanism-based irreversible route, forming an adduct with the pyridoxal 5′-phosphate cofactor, leading to bacterial death. Inconsistent with this hypothesis, Mycobacterium tuberculosis Alr activity can be detected after exposure to clinically relevant DCS concentrations. To address this paradox, we investigated the chemical mechanism of Alr inhibition by DCS. Inhibition of M. tuberculosis Alr and other Alrs is reversible, mechanistically revealed by a previously unidentified DCS-adduct hydrolysis. Dissociation and subsequent rearrangement to a stable substituted oxime explains Alr reactivation in the cellular milieu. This knowledge provides a novel route for discovery of improved Alr inhibitors against M. tuberculosis and other bacteria.
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Mar 2020
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I03-Macromolecular Crystallography
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Olivia J. S.
Macleod
,
Jean-mathieu
Bart
,
Paula
Macgregor
,
Lori
Peacock
,
Nicholas J.
Savill
,
Svenja
Hester
,
Sophie
Ravel
,
Jack D.
Sunter
,
Camilla
Trevor
,
Steven
Rust
,
Tristan J.
Vaughan
,
Ralph
Minter
,
Shabaz
Mohammed
,
Wendy
Gibson
,
Martin C.
Taylor
,
Matthew
Higgins
,
Mark
Carrington
Diamond Proposal Number(s):
[18069]
Open Access
Abstract: Persistent pathogens have evolved to avoid elimination by the mammalian immune system including mechanisms to evade complement. Infections with African trypanosomes can persist for years and cause human and animal disease throughout sub-Saharan Africa. It is not known how trypanosomes limit the action of the alternative complement pathway. Here we identify an African trypanosome receptor for mammalian factor H, a negative regulator of the alternative pathway. Structural studies show how the receptor binds ligand, leaving inhibitory domains of factor H free to inactivate complement C3b deposited on the trypanosome surface. Receptor expression is highest in developmental stages transmitted to the tsetse fly vector and those exposed to blood meals in the tsetse gut. Receptor gene deletion reduced tsetse infection, identifying this receptor as a virulence factor for transmission. This demonstrates how a pathogen evolved a molecular mechanism to increase transmission to an insect vector by exploitation of a mammalian complement regulator.
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Mar 2020
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Krios III-Titan Krios III at Diamond
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Francesca
Coscia
,
Ajda
Taler-verčič
,
Veronica T.
Chang
,
Ludwig
Sinn
,
Francis J.
O'reilly
,
Thierry
Izore
,
Miha
Renko
,
Imre
Berger
,
Juri
Rappsilber
,
Dušan
Turk
,
Jan
Lowe
Diamond Proposal Number(s):
[17434]
Abstract: Thyroglobulin (TG) is the protein precursor of thyroid hormones, which are essential for growth, development and the control of metabolism in vertebrates. Hormone synthesis from TG occurs in the thyroid gland via the iodination and coupling of pairs of tyrosines, and is completed by TG proteolysis3. Tyrosine proximity within TG is thought to enable the coupling reaction but hormonogenic tyrosines have not been clearly identified, and the lack of a three-dimensional structure of TG has prevented mechanistic understanding4. Here we present the structure of full-length human thyroglobulin at a resolution of approximately 3.5 Å, determined by cryo-electron microscopy. We identified all of the hormonogenic tyrosine pairs in the structure, and verified them using site-directed mutagenesis and in vitro hormone-production assays using human TG expressed in HEK293T cells. Our analysis revealed that the proximity, flexibility and solvent exposure of the tyrosines are the key characteristics of hormonogenic sites. We transferred the reaction sites from TG to an engineered tyrosine donor–acceptor pair in the unrelated bacterial maltose-binding protein (MBP), which yielded hormone production with an efficiency comparable to that of TG. Our study provides a framework to further understand the production and regulation of thyroid hormones.
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Feb 2020
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[13467]
Abstract: Cycloaddition reactions generate chemical complexity in a single step. Here we report the crystal structures of three homologous plant-derived cyclases involved in the biosynthesis of iboga and aspidosperma alkaloids. These enzymes act on the same substrate, named angryline, to generate three distinct scaffolds. Mutational analysis reveals how these highly similar enzymes control regio- and stereo-selectivity.
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Feb 2020
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I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[14739, 20229]
Open Access
Abstract: Histidine is a versatile residue playing key roles in enzyme catalysis thanks to the chemistry of its imidazole group that can serve as nucleophile, general acid or base depending on its protonation state. In bacteria, signal transduction relies on two-component systems (TCS) which comprise a sensor histidine kinase (HK) containing a phosphorylatable catalytic His with phosphotransfer and phosphatase activities over an effector response regulator. Recently, a pH-gated model has been postulated to regulate the phosphatase activity of HisKA HKs based on the pH-dependent rotamer switch of the phosphorylatable His. Here, we have revisited this model from a structural and functional perspective on HK853–RR468 and EnvZ–OmpR TCS, the prototypical HisKA HKs. We have found that the rotamer of His is not influenced by the environmental pH, ruling out a pH-gated model and confirming that the chemistry of the His is responsible for the decrease in the phosphatase activity at acidic pH.
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Feb 2020
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Marcin J.
Suskiewicz
,
Florian
Zobel
,
Tom E. H.
Ogden
,
Pietro
Fontana
,
Antonio
Ariza
,
Ji-chun
Yang
,
Kang
Zhu
,
Lily
Bracken
,
William J.
Hawthorne
,
Dragana
Ahel
,
David
Neuhaus
,
Ivan
Ahel
Diamond Proposal Number(s):
[9306, 18069]
Abstract: The anti-cancer drug target poly(ADP-ribose) polymerase 1 (PARP1) and its close homologue, PARP2, are early responders to DNA damage in human cells1,2. Upon binding to genomic lesions, these enzymes utilise NAD+ to modify a plethora of proteins with mono- and poly(ADP-ribose) signals that are important for subsequent chromatin decompaction and repair factor recruitment3,4. These post-translational modification events are predominantly serine-linked and require HPF1, an accessory factor that is specific for the DNA damage response and switches the amino-acid specificity of PARP1/2 from aspartate/glutamate to serine residues5–10. Here, we report a co-structure of HPF1 bound to the catalytic domain of PARP2 that, in combination with NMR and biochemical data, reveals a composite active site formed by residues from both PARP1/2 and HPF1. We further show that the assembly of this new catalytic centre is essential for DNA damage-induced protein ADP-ribosylation in human cells. In response to DNA damage and NAD+ binding site occupancy, the HPF1–PARP1/2 interaction is enhanced via allosteric networks operating within PARP1/2, providing an additional level of regulation in DNA repair induction. As HPF1 forms a joint active site with PARP1/2, our data implicate HPF1 as an important determinant of the response to clinical PARP inhibitors.
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Feb 2020
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I03-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[20113]
Open Access
Abstract: The human gut microbiota plays a central role not only in regulating the metabolism of nutrients but also promoting immune homeostasis, immune responses and protection against pathogen colonization. The genome of the Gram-negative symbiont Bacteroides thetaiotaomicron, a dominant member of the human intestinal microbiota, encodes polysaccharide utilization loci PULs, the apparatus required to orchestrate the degradation of a specific glycan. EndoBT-3987 is a key endo-β-N-acetylglucosaminidase (ENGase) that initiates the degradation/processing of mammalian high-mannose-type (HM-type) N-glycans in the intestine. Here, we provide structural snapshots of EndoBT-3987, including the unliganded form, the EndoBT-3987-Man9GlcNAc2Asn substrate complex, and two EndoBT-3987-Man9GlcNAc and EndoBT-3987-Man5GlcNAc product complexes. In combination with alanine scanning mutagenesis and activity measurements we unveil the molecular mechanism of HM-type recognition and specificity for EndoBT-3987 and an important group of the GH18 ENGases, including EndoH, an enzyme extensively used in biotechnology, and for which the mechanism of substrate recognition was largely unknown.
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Feb 2020
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[13639, 20876, 22610]
Abstract: Prussian blue analogues (PBAs) are a diverse family of microporous inorganic solids, known for their gas storage ability1, metal-ion immobilization2, proton conduction3, and stimuli-dependent magnetic4,5, electronic6 and optical7 properties. This family of materials includes the double-metal cyanide catalysts8,9 and the hexacyanoferrate/hexacyanomanganate battery materials10,11. Central to the various physical properties of PBAs is their ability to reversibly transport mass, a process enabled by structural vacancies. Conventionally presumed to be random12,13, vacancy arrangements are crucial because they control micropore-network characteristics, and hence the diffusivity and adsorption profiles14,15. The long-standing obstacle to characterizing the vacancy networks of PBAs is the inaccessibility of single crystals16. Here we report the growth of single crystals of various PBAs and the measurement and interpretation of their X-ray diffuse scattering patterns. We identify a diversity of non-random vacancy arrangements that is hidden from conventional crystallographic powder analysis. Moreover, we explain this unexpected phase complexity in terms of a simple microscopic model that is based on local rules of electroneutrality and centrosymmetry. The hidden phase boundaries that emerge demarcate vacancy-network polymorphs with very different micropore characteristics. Our results establish a foundation for correlated defect engineering in PBAs as a means of controlling storage capacity, anisotropy and transport efficiency.
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Feb 2020
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Krios IV-Titan Krios IV at Diamond
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Alister
Burt
,
C. Keith
Cassidy
,
Peter
Ames
,
Maria
Bacia-verloop
,
Megghane
Baulard
,
Karine
Huard
,
Zaida
Luthey-schulten
,
Ambroise
Desfosses
,
Phillip J.
Stansfeld
,
William
Margolin
,
John S.
Parkinson
,
Irina
Gutsche
Diamond Proposal Number(s):
[18112]
Open Access
Abstract: Motile bacteria sense chemical gradients with transmembrane receptors organised in supramolecular signalling arrays. Understanding stimulus detection and transmission at the molecular level requires precise structural characterisation of the array building block known as a core signalling unit. Here we introduce an Escherichia coli strain that forms small minicells possessing extended and highly ordered chemosensory arrays. We use cryo-electron tomography and subtomogram averaging to provide a three-dimensional map of a complete core signalling unit, with visible densities corresponding to the HAMP and periplasmic domains. This map, combined with previously determined high resolution structures and molecular dynamics simulations, yields a molecular model of the transmembrane core signalling unit and enables spatial localisation of its individual domains. Our work thus offers a solid structural basis for the interpretation of a wide range of existing data and the design of further experiments to elucidate signalling mechanisms within the core signalling unit and larger array.
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Feb 2020
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