I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I24-Microfocus Macromolecular Crystallography
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Jingshan
Ren
,
Joanne E.
Nettleship
,
Gemma
Harris
,
William
Mwangi
,
Nahid
Rhaman
,
Clare
Grant
,
Abhay
Kotecha
,
Elizabeth
Fry
,
Bryan
Charleston
,
David I.
Stuart
,
John
Hammond
,
Raymond J.
Owens
Diamond Proposal Number(s):
[10627, 14744]
Open Access
Abstract: Cattle antibodies have unusually long CDR3 loops in their heavy chains (HCs), and limited light chain (LC) diversity, raising the question of whether these mask the effect of LC variation on antigen recognition. We have investigated the role of the LC in the structure and activity of two neutralizing cattle antibodies (B4 and B13) that bind the F protein of bovine respiratory syncytial virus (bRSV). Recombinant Fab fragments of B4 and B13 bound bRSV infected cells and showed similar affinities for purified bRSV F protein. Exchanging the LCs between the Fab fragments produced hybrid Fabs: B13* (B13 HC/B4 LC) and B4* (B4 HC/B13 LC). The affinity of B13* to the F protein was found to be two-fold lower than B13 whilst the binding affinity of B4* was reduced at least a hundred-fold compared to B4 such that it no longer bound to bRSV infected cells. Comparison of the structures of B4 and B13 with their LC exchanged counterparts B4* and B13* showed that paratope of the HC variable domain (VH) of B4 was disrupted on pairing with the B13 LC, consistent with the loss of binding activity. By contrast, B13 H3 adopts a similar conformation when paired with either B13 or B4 LCs. These observations confirm the expected key role of the extended H3 loop in antigen-binding by cattle antibodies but also show that the quaternary LC/HC subunit interaction can be crucial for its presentation and thus the LC variable domain (VL) is also important for antigen recognition.
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Aug 2019
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I04-1-Macromolecular Crystallography (fixed wavelength)
I24-Microfocus Macromolecular Crystallography
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Faraz
Shaikh
,
Yuguang
Zhao
,
Luis
Alvarez
,
Maria
Iliopoulou
,
Christopher Thomas
Lohans
,
Christopher J.
Schofield
,
Sergi
Padilla-parra
,
Shirley W. I.
Siu
,
Elizabeth
Fry
,
Jingshan
Ren
,
David I.
Stuart
Diamond Proposal Number(s):
[10627]
Abstract: Potent Ebolavirus (EBOV) inhibitors will help to curtail outbreaks such as that which occurred in 2014-16 in West Africa. EBOV has on its surface a single glycoprotein (GP) critical for viral entry and membrane fusion. Recent high resolution complexes of EBOV GP with a variety of approved drugs revealed that binding to a common cavity prevented fusion of the virus and endosomal membranes, inhibiting virus infection. We performed docking experiments, screening a database of natural compounds to identify those likely to bind at this site. Using both inhibition assays of HIV-1-derived pseudovirus cell entry and structural analyses of the complexes of the compounds with GP we show here that two of these compounds attach in the common binding cavity, out of eight tested. In both cases two molecules bind in the cavity. The two compounds are chemically similar but the tighter binder has an additional chlorine atom that forms good halogen bonds to the protein and achieves an IC50 of 50 nM, making it the most potent GP-binding EBOV inhibitor yet identified, validating our screening approach for the discovery of novel anti-viral compounds.
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Feb 2019
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Abstract: Enterovirus 71 (EV71) is a common cause of hand, foot and mouth disease—a disease endemic especially in the Asia-Pacific region1. Scavenger receptor class B member 2 (SCARB2) is the major receptor of EV71, as well as several other enteroviruses responsible for hand, foot and mouth disease, and plays a key role in cell entry2. The isolated structures of EV71 and SCARB2 are known3,4,5,6, but how they interact to initiate infection is not. Here, we report the EV71–SCARB2 complex structure determined at 3.4 Å resolution using cryo-electron microscopy. This reveals that SCARB2 binds EV71 on the southern rim of the canyon, rather than across the canyon, as predicted3,7,8. Helices 152–163 (α5) and 183–193 (α7) of SCARB2 and the viral protein 1 (VP1) GH and VP2 EF loops of EV71 dominate the interaction, suggesting an allosteric mechanism by which receptor binding might facilitate the low-pH uncoating of the virus in the endosome/lysosome. Remarkably, many residues within the binding footprint are not conserved across SCARB2-dependent enteroviruses; however, a conserved proline and glycine seem to be key residues. Thus, although the virus maintains antigenic variability even within the receptor-binding footprint, the identification of binding ‘hot spots’ may facilitate the design of receptor mimic therapeutics less likely to quickly generate resistance.
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Dec 2018
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Krios I-Titan Krios I at Diamond
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Abhay
Kotecha
,
Eva
Perez-martin
,
Yongjie
Harvey
,
Fuquan
Zhang
,
Serban L.
Ilca
,
Elizabeth E.
Fry
,
Ben
Jackson
,
Francois
Maree
,
Katherine
Scott
,
Corey W.
Hecksel
,
Michiel M.
Harmsen
,
Valérie
Mioulet
,
Britta
Wood
,
Nick
Juleff
,
David I.
Stuart
,
Bryan
Charleston
,
Julian
Seago
Open Access
Abstract: Foot-and-mouth disease virus (FMDV) is highly contagious and infects cloven-hoofed domestic livestock leading to foot-and-mouth disease (FMD). FMD outbreaks have severe economic impact due to production losses and associated control measures. FMDV is found as seven distinct serotypes, but there are numerous subtypes within each serotype, and effective vaccines must match the subtypes circulating in the field. In addition, the O and Southern African Territories (SAT) serotypes, are relatively more thermolabile and their viral capsids readily dissociate into non-immunogenic pentameric subunits, which can compromise the effectiveness of FMD vaccines. Here we report the construction of a chimeric clone between the SAT2 and O serotypes, designed to have SAT2 antigenicity. Characterisation of the chimeric virus showed growth kinetics equal to that of the wild type SAT2 virus with better thermostability, attributable to changes in the VP4 structural protein. Sequence and structural analyses confirmed that no changes from SAT2 were present elsewhere in the capsid as a consequence of the VP4 changes. Following exposure to an elevated temperature the thermostable SAT2-O1K chimera induced higher neutralizing-antibody titres in comparison to wild type SAT2 virus.
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Sep 2018
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Gareth
Shimmon
,
Abhay
Kotecha
,
Jingshan
Ren
,
Amin S.
Asfor
,
Joseph
Newman
,
Stephen
Berryman
,
Eleanor M.
Cottam
,
Sarah
Gold
,
Toby J.
Tuthill
,
Donald P.
King
,
Emiliana
Brocchi
,
Andrew M. Q.
King
,
Ray
Owens
,
Elizabeth E.
Fry
,
David I.
Stuart
,
Alison
Burman
,
Terry
Jackson
Open Access
Abstract: Foot-and-mouth disease (FMD) affects economically important livestock and is one of the most contagious viral diseases. The most commonly used FMD diagnostic assay is a sandwich ELISA. However, the main disadvantage of this ELISA is that it requires anti-FMD virus (FMDV) serotype-specific antibodies raised in small animals. This problem can be, in part, overcome by using anti-FMDV monoclonal antibodies (MAbs) as detecting reagents. However, the long-term use of MAbs may be problematic and they may need to be replaced. Here we have constructed chimeric antibodies (mouse/rabbit D9) and Fabs (fragment antigen-binding) (mouse/cattle D9) using the Fv (fragment variable) regions of a mouse MAb, D9 (MAb D9), which recognises type O FMDV. The mouse/rabbit D9 chimeric antibody retained the FMDV serotype-specificity of MAb D9 and performed well in a FMDV detection ELISA as well as in routine laboratory assays. Cryo-electron microscopy analysis confirmed engagement with antigenic site 1 and peptide competition studies identified the aspartic acid at residue VP1 147 as a novel component of the D9 epitope. This chimeric expression approach is a simple but effective way to preserve valuable FMDV antibodies, and has the potential for unlimited generation of antibodies and antibody fragments in recombinant systems with the concomitant positive impacts on the 3Rs (Replacement, Reduction and Refinement) principles.
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Aug 2018
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I03-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[6387, 8423]
Abstract: Hepatitis A virus (HAV) has been enigmatic, evading detailed structural analysis for many years. Its recently determined high-resolution structure revealed an angular surface without the indentations often characteristic of receptor-binding sites. The viral protein 1 (VP1) β-barrel shows no sign of a pocket factor and the amino terminus of VP2 displays a “domain swap” across the pentamer interface, as in a subset of mammalian picornaviruses and insect picorna-like viruses. Structure-based phylogeny confirms this placement. These differences suggest an uncoating mechanism distinct from that of enteroviruses. An empty capsid structure reveals internal differences in VP0 and the VP1 amino terminus connected with particle maturation. An HAV/Fab complex structure, in which the antigen-binding fragment (Fab) appears to act as a receptor–mimic, clarifies some historical epitope mapping data, but some remain difficult to reconcile. We still have little idea of the structural features of enveloped HAV particles.
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Jul 2018
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I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[10627]
Abstract: A large number of Food and Drug Administration (FDA) approved drugs have been found to inhibit cell entry of Ebola virus (EBOV). However, since these drugs have various primary pharmacological targets their mechanisms of action against EBOV remain largely unknown. We have previously shown that six FDA approved drugs inhibit EBOV infection by interacting with and destabilizing the viral glycoprotein (GP). Here we show that the antidepressants imipramine and clomipramine, and antipsychotic drug thioridazine also directly interact with EBOV GP, and determine the mode of interaction by crystallographic analysis of the complexes. The compounds bind within the same pocket as observed for other, chemically divergent, complexes but with different binding modes. These details should be of value for the development of potent EBOV inhibitors.
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May 2018
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I02-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[10627]
Abstract: Here we show that four chemically divergent approved drugs reported to inhibit Ebolavirus infection, benztropine, bepridil, paroxetine and sertraline, directly interact with the Ebolavirus glycoprotein. Binding of these drugs destabilise the protein, suggesting that this may be the mechanism of inhibition, as reported for the anticancer drug toremifene and the painkiller ibuprofen, which bind in the same large cavity on the glycoprotein. Crystal structures show that the position of binding and the mode of interaction within the pocket vary significantly between these compounds. The binding constants (Kd) determined by thermal shift assay correlate with the protein-inhibitor interactions as well as with the antiviral activities determined by virus cell entry assays, supporting the hypothesis that these drugs inhibit viral entry by binding the glycoprotein and destabilising the pre-fusion conformation. Details of the protein–inhibitor interactions of these complexes and their relation with binding affinity may facilitate the design of more potent inhibitors.
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Dec 2017
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M01-Polara at OPIC (Oxford)
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Open Access
Abstract: Foot-and-mouth disease virus (FMDV) belongs to the aphthovirus genus of the Picornaviridae, a family of small, icosahedral, non-enveloped, single-stranded RNA viruses. It is a highly infectious pathogen and is one of the biggest hindrances to the international trade of animals and animal products. FMDV capsids (which are unstable below pH6.5) release their genome into the host cell from an acidic compartment, such as that of an endosome, and in the process dissociate into pentamers. Whilst other members of the family (enteroviruses) have been visualized to form an expanded intermediate capsid with holes from which inner capsid proteins (VP4), N-termini (VP1) and RNA can be released, there has been no visualization of any such state for an aphthovirus, instead the capsid appears to simply dissociate into pentamers. Here we present the 8-Å resolution structure of isolated dissociated pentamers of FMDV, lacking VP4. We also found these pentamers to re-associate into a rigid, icosahedrally symmetric assembly, which enabled their structure to be solved at higher resolution (5.2 Å). In this assembly, the pentamers unexpectedly associate ‘inside out’, but still with their exposed hydrophobic edges buried. Stabilizing interactions occur between the HI loop of VP2 and its symmetry related partners at the icosahedral 3-fold axes, and between the BC and EF loops of VP3 with the VP2 βB-strand and the CD loop at the 2-fold axes. A relatively extensive but subtle structural rearrangement towards the periphery of the dissociated pentamer compared to that in the mature virus provides insight into the mechanism of dissociation of FMDV and the marked difference in antigenicity.
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Sep 2017
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Krios I-Titan Krios I at Diamond
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Open Access
Abstract: Poliovirus (PV) is the causative agent of poliomyelitis, a crippling human disease known since antiquity. PV occurs in two distinct antigenic forms, D and C, of which only the D form elicits a robust neutralizing response. Developing a synthetically produced stabilized virus-like particle (sVLP)-based vaccine with D antigenicity, without the drawbacks of current vaccines, will be a major step towards the final eradication of poliovirus. Such a sVLP would retain the native antigenic conformation and the repetitive structure of the original virus particle, but lack infectious genomic material. In this study, we report the production of synthetically stabilized PV VLPs in plants. Mice carrying the gene for the human PV receptor are protected from wild-type PV when immunized with the plant-made PV sVLPs. Structural analysis of the stabilized mutant at 3.6 Å resolution by cryo-electron microscopy and single-particle reconstruction reveals a structure almost indistinguishable from wild-type PV3.
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Aug 2017
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