I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Andrew
Chancellor
,
Robert A.
Simmons
,
Rahul C.
Khanolkar
,
Vladimir
Nosi
,
Aisha
Beshirova
,
Giuliano
Berloffa
,
Rodrigo
Colombo
,
Vijaykumar
Karuppiah
,
Johanne M.
Pentier
,
Vanessa
Tubb
,
Hemza
Ghadbane
,
Richard J.
Suckling
,
Keith
Page
,
Rory M.
Crean
,
Alessandro
Vacchini
,
Corinne
De Gregorio
,
Verena
Schaefer
,
Daniel
Constantin
,
Thomas
Gligoris
,
Angharad
Lloyd
,
Miriam
Hock
,
Velupillai
Srikannathasan
,
Ross A.
Robinson
,
Gurdyal S.
Besra
,
Marc W.
Van Der Kamp
,
Lucia
Mori
,
Raffaele
Calogero
,
David K.
Cole
,
Gennaro
De Libero
,
Marco
Lepore
Diamond Proposal Number(s):
[22870, 28224]
Abstract: Mucosal-associated invariant T (MAIT) cells use canonical semi-invariant T cell receptors (TCR) to recognize microbial riboflavin precursors displayed by the antigen-presenting molecule MR1. The extent of MAIT TCR crossreactivity toward physiological, microbially unrelated antigens remains underexplored. We describe MAIT TCRs endowed with MR1-dependent reactivity to tumor and healthy cells in the absence of microbial metabolites. MAIT cells bearing TCRs crossreactive toward self are rare but commonly found within healthy donors and display T-helper-like functions in vitro. Experiments with MR1-tetramers loaded with distinct ligands revealed significant crossreactivity among MAIT TCRs both ex vivo and upon in vitro expansion. A canonical MAIT TCR was selected on the basis of extremely promiscuous MR1 recognition. Structural and molecular dynamic analyses associated promiscuity to unique TCRβ-chain features that were enriched within self-reactive MAIT cells of healthy individuals. Thus, self-reactive recognition of MR1 represents a functionally relevant indication of MAIT TCR crossreactivity, suggesting a potentially broader role of MAIT cells in immune homeostasis and diseases, beyond microbial immunosurveillance.
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Sep 2023
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I04-Macromolecular Crystallography
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Katja
Zorn
,
Catherine R.
Back
,
Rob
Barringer
,
Veronika
Chadimová
,
Monserrat
Manzo-Ruiz
,
Sbusisiwe Z.
Mbatha
,
Juan-Carlos
Mobarec
,
Sam E.
Williams
,
Marc W.
Van Der Kamp
,
Paul R.
Race
,
Christine L.
Willis
,
Martin Alistair
Hayes
Diamond Proposal Number(s):
[23269]
Abstract: Stereoselective carbon-carbon bond forming reactions are quintessential transformations in organic synthesis. One example is the Diels-Alder reaction, a [4+2] cycloaddition between a conjugated diene and a dienophile to form cyclohexenes. The development of biocatalysts for this reaction is paramount for unlocking sustainable routes to a plethora of important molecules. To obtain a comprehensive understanding of naturally evolved [4+2] cyclases, and to identify hitherto uncharacterised biocatalysts for this reaction, we constructed a library comprising forty-five enzymes with reported or predicted [4+2] cycloaddition activity. Thirty-one library members were successfully produced in recombinant form. In vitro assays employing a synthetic substrate incorporating a diene and a dienophile revealed broad-ranging cycloaddition activity amongst these polypeptides. The hypothetical protein Cyc15 was found to catalyse an intramolecular cycloaddition to generate a novel spirotetronate. The crystal structure of this enzyme, along with docking studies, establishes the basis for stereoselectivity in Cyc15, as compared to other spirotetronate cyclases.
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Jun 2023
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Andrew J.
Devine
,
Alice E.
Parnell
,
Catherine R.
Back
,
Nicholas R.
Lees
,
Samuel T.
Johns
,
Ainul Z.
Zulkepli
,
Rob
Barringer
,
Katja
Zorn
,
James E. M.
Stach
,
Matthew P.
Crump
,
Martin A.
Hayes
,
Marc W.
Van Der Kamp
,
Paul R.
Race
,
Christine
Willis
Open Access
Abstract: Abyssomicin C and its atropisomer are potent inhibitors of bacterial folate metabolism. They possess complex polycyclic structures, and their biosynthesis has been shown to involve several unusual enzymatic transformations. Using a combination of synthesis and in vitro assays we reveal that AbyV, a cytochrome P450 enzyme from the aby gene cluster, catalyses a key late-stage epoxidation required for the installation of the characteristic ether-bridged-core of abyssomicin C. The X-ray crystal structure of AbyV has been determined, which in combination with molecular dynamics simulations provides a structural framework for our functional data. This work demonstrates the power of combining selective carbon-13 labelling with NMR spectroscopy as a sensitive tool to interrogate enzyme-catalysed reactions in vitro with no need for purification.
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Oct 2022
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
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Andrew
Poole
,
Vijaykumar
Karuppiah
,
Annabelle
Hartt
,
Jaafar N.
Haidar
,
Sylvie
Moureau
,
Tomasz
Dobrzycki
,
Conor
Hayes
,
Christopher
Rowley
,
Jorge
Dias
,
Stephen
Harper
,
Keir
Barnbrook
,
Miriam
Hock
,
Charlotte
Coles
,
Wei
Yang
,
Milos
Aleksic
,
Aimee Bence
Lin
,
Ross
Robinson
,
Joe D.
Dukes
,
Nathaniel
Liddy
,
Marc
Van Der Kamp
,
Gregory D.
Plowman
,
Annelise
Vuidepot
,
David K.
Cole
,
Andrew D.
Whale
,
Chandramouli
Chillakuri
Diamond Proposal Number(s):
[22870]
Open Access
Abstract: Neoantigens derived from somatic mutations are specific to cancer cells and are ideal targets for cancer immunotherapy. KRAS is the most frequently mutated oncogene and drives the pathogenesis of several cancers. Here we show the identification and development of an affinity-enhanced T cell receptor (TCR) that recognizes a peptide derived from the most common KRAS mutant, KRASG12D, presented in the context of HLA-A*11:01. The affinity of the engineered TCR is increased by over one million-fold yet fully able to distinguish KRASG12D over KRASWT. While crystal structures reveal few discernible differences in TCR interactions with KRASWT versus KRASG12D, thermodynamic analysis and molecular dynamics simulations reveal that TCR specificity is driven by differences in indirect electrostatic interactions. The affinity enhanced TCR, fused to a humanized anti-CD3 scFv, enables selective killing of cancer cells expressing KRASG12D. Our work thus reveals a molecular mechanism that drives TCR selectivity and describes a soluble bispecific molecule with therapeutic potential against cancers harboring a common shared neoantigen.
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Sep 2022
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[1226]
Open Access
Abstract: A 2-keto-3-deoxygluconate aldolase from the hyperthermophile Sulfolobus solfataricus catalyzes the nonstereoselective aldol reaction of pyruvate and d-glyceraldehyde to produce 2-keto-3-deoxygluconate (d-KDGlc) and 2-keto-3-deoxy-d-galactonate (d-KDGal). Previous investigations into curing the stereochemical promiscuity of this hyperstable aldolase used high-resolution structures of the aldolase bound to d-KDGlc or d-KDGal to identify critical amino acids involved in substrate binding for mutation. This structure-guided approach enabled mutant variants to be created that could stereoselectively catalyze the aldol reaction of pyruvate and natural d-glyceraldehyde to selectively afford d-KDGlc or d-KDGal. Here we describe the creation of two further mutants of this Sulfolobus aldolase that can be used to catalyze aldol reactions between pyruvate and non-natural l-glyceraldehyde to enable the diastereoselective synthesis of l-KDGlc and l-KDGal. High-resolution crystal structures of all four variant aldolases have been determined (both unliganded and liganded), including Variant 1 with d-KDGlc, Variant 2 with pyruvate, Variant 3 with l-KDGlc, and Variant 4 with l-KDGal. These structures have enabled us to rationalize the observed changes in diastereoselectivities in these variant-catalyzed aldol reactions at a molecular level. Interestingly, the active site of Variant 4 was found to be sufficiently flexible to enable catalytically important amino acids to be replaced while still retaining sufficient enzymic activity to enable production of l-KDGal.
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Sep 2022
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I02-Macromolecular Crystallography
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Rory M.
Crean
,
Bruce J.
Maclachlan
,
Florian
Madura
,
Thomas
Whalley
,
Pierre J.
Rizkallah
,
Christopher J.
Holland
,
Catriona
Mcmurran
,
Stephen
Harper
,
Andrew
Godkin
,
Andrew K.
Sewell
,
Christopher R.
Pudney
,
Marc W.
Van Der Kamp
,
David K.
Cole
Diamond Proposal Number(s):
[6232]
Open Access
Abstract: Immuno-oncology approaches that utilise T cell receptors (TCRs) are becoming highly attractive because of their potential to target virtually all cellular proteins, including cancer specific epitopes, via the recognition of peptide-human leukocyte antigen complexes (pHLA) presented at the cell surface. However, because natural TCRs generally recognise cancer derived pHLAs with very weak affinities, efforts have been made to enhance their binding strength, in some cases by several million-fold. Here, we investigated the mechanisms underpinning human TCR affinity enhancement by comparing the crystal structures of engineered enhanced affinity TCRs with that of their wildtype progenitors. Additionally, we performed molecular dynamics simulations to better understand the energetic mechanisms driving the affinity enhancements. These data demonstrate that supra-physiological binding affinities can be achieved without altering native TCR-pHLA binding modes via relatively subtle modifications to the interface contacts, often driven through the addition of buried hydrophobic residues. Individual energetic components of the TCR-pHLA interaction governing affinity enhancements were distinct and highly variable for each TCR, often resulting from additive, or knock-on, effects beyond the mutated residues. This comprehensive analysis of affinity enhanced TCRs has important implications for the future rational design of engineered TCRs as efficacious and safe drugs for cancer treatment.We demonstrate that the native TCR-pHLA conformation is compatible with supra-physiological binding affinities via subtle modifications to the interface contacts, often driven through the addition of buried hydrophobic residues. This comprehensive analysis of affinity enhanced TCRs has important implications for the future rational design of engineered TCRs for cancer therapy.
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Jul 2020
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Christopher J.
Holland
,
Rory M.
Crean
,
Johanne M.
Pentier
,
Ben
De Wet
,
Angharad
Lloyd
,
Velupillai
Srikannathasan
,
Nikolai
Lissin
,
Katy A.
Lloyd
,
Thomas H.
Blicher
,
Paul J.
Conroy
,
Miriam
Hock
,
Robert J.
Pengelly
,
Thomas E.
Spinner
,
Brian
Cameron
,
Elizabeth A.
Potter
,
Anitha
Jeyanthan
,
Peter E.
Molloy
,
Malkit
Sami
,
Milos
Aleksic
,
Nathaniel
Liddy
,
Ross A.
Robinson
,
Stephen
Harper
,
Marco
Lepore
,
Chris R.
Pudney
,
Marc W.
Van Der Kamp
,
Pierre J.
Rizkallah
,
Bent K.
Jakobsen
,
Annelise
Vuidepot
,
David K.
Cole
Diamond Proposal Number(s):
[17077, 14843]
Abstract: Tumor-associated peptide–human leukocyte antigen complexes (pHLAs) represent the largest pool of cell surface–expressed cancer-specific epitopes, making them attractive targets for cancer therapies. Soluble bispecific molecules that incorporate an anti-CD3 effector function are being developed to redirect T cells against these targets using 2 different approaches. The first achieves pHLA recognition via affinity-enhanced versions of natural TCRs (e.g., immune-mobilizing monoclonal T cell receptors against cancer [ImmTAC] molecules), whereas the second harnesses an antibody-based format (TCR-mimic antibodies). For both classes of reagent, target specificity is vital, considering the vast universe of potential pHLA molecules that can be presented on healthy cells. Here, we made use of structural, biochemical, and computational approaches to investigate the molecular rules underpinning the reactivity patterns of pHLA-targeting bispecifics. We demonstrate that affinity-enhanced TCRs engage pHLA using a comparatively broad and balanced energetic footprint, with interactions distributed over several HLA and peptide side chains. As ImmTAC molecules, these TCRs also retained a greater degree of pHLA selectivity, with less off-target activity in cellular assays. Conversely, TCR-mimic antibodies tended to exhibit binding modes focused more toward hot spots on the HLA surface and exhibited a greater degree of crossreactivity. Our findings extend our understanding of the basic principles that underpin pHLA selectivity and exemplify a number of molecular approaches that can be used to probe the specificity of pHLA-targeting molecules, aiding the development of future reagents.
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Apr 2020
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[15378]
Open Access
Abstract: Indanomycin is biosynthesized by a hybrid nonribosomal peptide synthase/polyketide synthase (NRPS/PKS) followed by a number of `tailoring' steps to form the two ring systems that are present in the mature product. It had previously been hypothesized that the indane ring of indanomycin was formed by the action of IdmH using a Diels–Alder reaction. Here, the crystal structure of a selenomethionine-labelled truncated form of IdmH (IdmH-Δ99–107) was solved using single-wavelength anomalous dispersion (SAD) phasing. This truncated variant allows consistent and easy crystallization, but importantly the structure was used as a search model in molecular replacement, allowing the full-length IdmH structure to be determined to 2.7 Å resolution. IdmH is a homodimer, with the individual protomers consisting of an α+β barrel. Each protomer contains a deep hydrophobic pocket which is proposed to constitute the active site of the enzyme. To investigate the reaction catalysed by IdmH, 88% of the backbone NMR resonances were assigned, and using chemical shift perturbation of [15N]-labelled IdmH it was demonstrated that indanomycin binds in the active-site pocket. Finally, combined quantum mechanical/molecular mechanical (QM/MM) modelling of the IdmH reaction shows that the active site of the enzyme provides an appropriate environment to promote indane-ring formation, supporting the assignment of IdmH as the key Diels–Alderase catalysing the final step in the biosynthesis of indanomycin through a similar mechanism to other recently characterized Diels–Alderases involved in polyketide-tailoring reactions. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at https://proteopedia.org/w/Journal:IUCrJ:S2052252519012399.
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Nov 2019
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I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Abstract: Spirotetronate and spirotetramate natural products include a multitude of compounds with potent antimicrobial and antitumor activities. Their biosynthesis incorporates many unusual biocatalytic steps, including regio‐ and stereo‐specific modifications, cyclizations promoted by Diels–Alderases, and acetylation‐elimination reactions. Here we focus on the acetate elimination catalyzed by AbyA5, implicated in the formation of the key Diels–Alder substrate to give the spirocyclic system of the antibiotic abyssomicin C. Using synthetic substrate analogues, it is shown that AbyA5 catalyzes stereospecific acetate elimination, establishing the (R)‐tetronate acetate as a biosynthetic intermediate. The X‐ray crystal structure of AbyA5, the first of an acetate‐eliminating enzyme, reveals a deviant acetyl esterase fold. Molecular dynamics simulations and enzyme assays show the use of a His‐Ser dyad to catalyze either elimination or hydrolysis, via disparate mechanisms, under substrate control.
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Jan 2019
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[12342]
Abstract: Oxygen heterocycles—in particular, tetrahydropyrans (THPs) and tetrahydrofurans—are common structural features of many biologically active polyketide natural products. Mupirocin is a clinically important antibiotic isolated from Pseudomonas fluorescens and is assembled on a THP ring, which is essential for bioactivity. However, the biosynthesis of this moiety has remained elusive. Here, we show an oxidative enzyme-catalysed cascade that generates the THP ring of mupirocin. Rieske non-haem oxygenase (MupW)-catalysed selective oxidation of the C8–C16 single bond in a complex acyclic precursor is combined with an epoxide hydrolase (MupZ) to catalyse the subsequent regioselective ring formation to give the hydroxylated THP. In the absence of MupZ, a five-membered tetrahydrofuran ring is isolated, and model studies are consistent with cyclization occurring via an epoxide intermediate. High-resolution X-ray crystallographic studies, molecular modelling and mutagenesis experiments of MupZ provide insights into THP ring formation proceeding via an anti-Baldwin 6-endo-tet cyclization.
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Dec 2018
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