I03-Macromolecular Crystallography
|
Diamond Proposal Number(s):
[36097]
Open Access
Abstract: The tRNA m1G37 methyltransferase (TrmD) is considered essential in various bacteria, including Staphylococcus aureus, a pathogen responsible for a wide range of diseases. Here, we have performed a high-throughput nanomole-scale synthesis campaign (nanoSAR) by late-stage copper(I)-catalyzed alkyne–azide cycloaddition (CuAAC)-functionalizing a library of structurally diverse azides (N = 320) to a pyrrolopyrimidone alkyne. We have identified selective S. aureus TrmD inhibitors with inhibitory activity in the nanomolar to low micromolar range using a direct-to-biology assay read-out. A carbamate-masked guanidine intermediate of the lead structure selectively inhibited S. aureus growth at low micromolar concentrations in cell-based assays, while Gram-negative bacteria and an off-target panel of methyltransferases were not affected. Subsequent cocrystallization resulted in a crystal structure of S. aureus TrmD bound to an inhibitor, providing detailed insights into its binding mode and enabling future structure-guided optimization.
|
Dec 2025
|
|
I04-Macromolecular Crystallography
|
Diamond Proposal Number(s):
[35689]
Open Access
Abstract: Bacterial multidrug resistance (MDR) poses a major threat to global health. The continued use of antibiotics, combined with genetic variations and exposure to nosocomial infections, has led to the selection and spread of multidrug-resistant bacteria. In recent years, photopharmacology has emerged as a strategy to combat MDR by enabling precise, light-controlled spatiotemporal modulation of the biological activity of photo-switchable compounds. Among different microbial species, Pseudomonas aeruginosa is a prominent bacterium involved in acute and chronic lung infections, posing a significant health concern, particularly among hospitalized and immunocompromised patients. The bacterium's capacity to form biofilms, a key factor in the development of MDR, is closely linked to the activity of the virulence factor LecB, a carbohydrate-binding protein with a well-documented role in biofilm formation. In this study, we report the design, synthesis and biological evaluation of two novel photoswitchable LecB modulators, photofucose-1 and photofucose-2. Isothermal Titration Calorimetry (ITC) analysis revealed that photofucose-2 binds LecB with high affinity, exhibiting a distinct difference in dissociation constants (Kd) between its cis and trans isomers. Moreover, we determined the X-ray crystal structure of the LecB-photofucose-2 complex, offering insights into its binding mechanism. These findings lay the groundwork for the rational, structure-based design of novel light-responsive compounds targeting LecB and represent a potential new avenue in the development of innovative strategies to combat bacterial resistance.
|
Dec 2025
|
|
I04-Macromolecular Crystallography
|
Chao
Li
,
Mia
Urem
,
Ioli
Kotsogianni
,
Josephine
Lau
,
Chao
Du
,
Somayah S.
Elsayed
,
Nathaniel I.
Martin
,
Iain W.
Mcnae
,
Patrick
Voskamp
,
Christoph
Mayer
,
Sébastien
Rigali
,
Navraj
Pannu
,
Jan P.
Abrahams
,
Lennart
Schada Von Borzyskowski
,
Gilles P.
Van Wezel
Diamond Proposal Number(s):
[18515]
Open Access
Abstract: Streptomyces bacteria are renowned for their multicellular lifestyle and as Nature’s medicine makers, producing the majority of the clinical antibiotics. A landmark event during early development is the lytic dismantling of the substrate mycelium. Degradation of the hyphal cell-wall leads to the accumulation of N-acetylglucosamine (GlcNAc) in the colonies, which is a metabolic checkpoint during the onset of development and antibiotic production. Here, we show that GlcNAc sensing requires a toxicity pathway dependent on the enzyme GlcNAc-6P dehydratase (NagS). Dehydration of GlcNAc-6P by NagS to 6P-chromogen I is an unprecedented reaction in central metabolism that is highly conserved in – and limited to – the Streptomycetaceae. 6P-chromogen I is metabolized into a structural analogue of ribose by a promiscuous activity of GlcNAc-6P deacetylase NagA. Toxicity is relieved by supplementing the growth media with ribose. Structure-function analysis of NagS not only highlighted key residues in the active site of the enzyme in interaction with its substrate GlcNAc-6P, but also revealed 6-phosphogluconate as its catalytic inhibitor. Our work uncovers a conserved metabolic toxicity pathway in Streptomyces that revolves around a novel enzyme that plays a key role in nutrient signaling.
|
Nov 2025
|
|
I03-Macromolecular Crystallography
|
Gabriela
D'Amico González
,
María Margarita
Rodríguez
,
Pedro
Penzotti
,
Florencia
Brunetti
,
Barbara
Ghiglione
,
Luke A.
Moe
,
Daniela
Centrón
,
Gabriel
Gutkind
,
Lin
Gao
,
Shozeb
Haider
,
Rachel A.
Powers
,
Sebastián
Klinke
,
Pablo
Power
Diamond Proposal Number(s):
[29507]
Open Access
Abstract: Wild-type LRA-5, recovered from Alaskan soil samples, shares no more than 33% amino acid sequence identity with enzymes from pathogens like PER β-lactamases. Recombinant E. coli expressing wild-type LRA-5 and its engineered variants LRA-5Y69Q and LRA-5V166E showed MIC values equivalent to control strains. However, LRA-5Y69Q/V166E displayed MICs above the resistant breakpoint for some β-lactams. Kinetic parameters correlated with the MICs, showing that the catalytic efficiency of LRA-5Y69Q/V166E was comparable to those from class A β-lactamases, such as CTX-M-15, PER-2, and KPC-2. LRA-5Y69Q/V166E exhibited kcat/Km values up to 11,000-fold higher compared to wild-type LRA-5, which is associated with the presence of Glu166. The X-ray crystallographic structure of wild-type LRA-5 (1.80 Å; PDB 8EO5) shows that the lack of both Glu166 and a deacylation water molecule contributes to a biologically insignificant activity. Interactions observed between LRA-5 and ceftazidime (2.35 Å; PDB 8EO6) show structural conservation with other β-lactamases. In contrast, the crystallographic structure of LRA-5Y69Q/V166E (2.15 Å; PDB 8EO7) bears a deacylation water molecule that is associated with the increase in catalytic activity compared to the wild-type variant. Circular dichroism results confirm that amino acid substitutions in LRA-5 do not affect the overall content of the secondary/tertiary structures. Evidence suggests that alternative evolutionary paths could have occurred for β-lactamases like LRA-5, produced by environmental microorganisms: (i) proteins having similar structural features than active β-lactamases may accumulate a small number of mutations (e.g., Y69Q/V166E) to yield active enzymes and (ii) the β-lactamase fold may have lost key residues in the absence of antibiotics.
|
Nov 2025
|
|
B21-High Throughput SAXS
|
Diamond Proposal Number(s):
[33176, 35926]
Open Access
Abstract: Mycobacterial infections, including tuberculosis, remain a major global health challenge, causing millions of deaths annually. Their treatment is increasingly hindered by limited therapeutic options and rising antimicrobial resistance, highlighting the urgent need for alternative strategies. Mycobacteriophage LysA endolysins are complex multi-domain peptidoglycan hydrolases emerging as potential tools to treat mycobacterial infections. However, despite the therapeutic prospects of LysAs, our understanding of their mechanism of action remains limited. This study provides a comprehensive structural-functional analysis of the catalytic domains of D29LysA and DS6ALysA endolysins (D29N4/D29GH19 and DS6AGH19/DS6AAmi2B), characterised alone and in complex with PG analogues, using protein engineering, X-ray crystallography, small-angle X-ray scattering, and in silico tools. Our results reveal precise details of the substrate-binding site and the catalytic platforms at each domain, including information about substrate-binding mode and conformational changes associated with peptidoglycan recognition and hydrolysis. Moreover, these findings also suggest a coordinated mechanism of action of both catalytic domains in DS6ALysA lysin. These insights represent a significant advance in understanding the structural basis of mycobacterial cell-wall degradation by mycobacteriophage endolysins. Information that may aid in further exploring these endolysins as therapeutic antimicrobial tools in the future.
|
Nov 2025
|
|
B21-High Throughput SAXS
|
Cassandra R.
Kennedy
,
Katherine A.
Mcphie
,
Aini
Vuorinen
,
Jane
Dudley-Fraser
,
Diego
Esposito
,
Sarah
Maslen
,
William J.
Mccarthy
,
Jonathan
Pettinger
,
J. Mark
Skehel
,
David
House
,
Katrin
Rittinger
,
Jacob
Bush
Diamond Proposal Number(s):
[32711]
Open Access
Abstract: As the global fight against antimicrobial resistance in bacteria becomes increasingly pressing, new tool compounds are needed to study and evaluate novel therapeutic targets. Here, cysteine-directed fragment-based drug discovery is coupled with high throughput chemistry direct-to-biology screening to target the catalytic cysteine of a family of bacterial effector proteins, the novel E3 ligases (NELs) from Salmonella and Shigella. These effector E3 ligases are attractive as potential drug targets because they are delivered into host cells during infection, have no human homologues and disrupt host immune response to infection. We successfully identify hit compounds against the SspH subfamily of NELs from Salmonella and show that these proteins are inhibited by compound treatment, representing an exciting starting point for development into specific and potent tool compounds.
|
Oct 2025
|
|
B23-Circular Dichroism
|
Open Access
Abstract: The emergence of multidrug-resistant (MDR) bacterial pathogens is an alarming global health threat that demands new therapeutic strategies beyond conventional antibiotics. Here, we present a rationally designed antimicrobial peptide (AMP) derived from mammalian cathelicidins and defensins that selectively targets bacterial membranes with low cytotoxicity toward mammalian cells. Circular dichroism spectroscopy revealed that the peptide adopts an α-helical conformation upon membrane interaction, a key feature of its mechanism. Surface plasmon resonance and isothermal titration calorimetry demonstrated high-affinity and selective binding to bacterial lipid membranes. Functionally, the peptide was strongly bactericidal against clinical MDR Escherichia coli (E. coli) and clinically important ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.). Compared with the parent peptide LL-37, our AMP exhibited lower minimum inhibitory concentrations (MICs) and faster bactericidal kinetics across both Gram-negative and Gram-positive strains. Calcein leakage assays, showing effective membrane disruption. Importantly, cytotoxicity experiments with human epithelial (Caco-2) and immune (THP-1) cells indicated low cytotoxicity at concentrations exceeding bactericidal levels, supporting a favorable therapeutic window. ELISA quantifications of cytokines (IL-6, TNF-α) further suggested immunomodulatory effects at bactericidal concentrations. Transcriptomic profiling of E. coli treated with sub-lethal concentrations of the peptide exhibited upregulation of bacterial stress response pathways and downregulation of vital metabolic processes, reflecting the complex antimicrobial action of the peptide. Collectively, these findings highlight this LL-37-derived AMP as a promising candidate for treating MDR bacterial infections caused by E. coli and ESKAPE pathogens and for guiding the development of next-generation antimicrobial agents.
|
Oct 2025
|
|
I03-Macromolecular Crystallography
|
Michael
Beer
,
Philip
Hinchliffe
,
Marko
Hanževački
,
Christopher R.
Bethel
,
Catherine L.
Tooke
,
Marc W.
Van Der Kamp
,
Krisztina M.
Papp‐wallace
,
Robert A.
Bonomo
,
Stuart
Shapiro
,
Adrian J.
Mulholland
,
James
Spencer
Diamond Proposal Number(s):
[23269, 31440]
Open Access
Abstract: β-Lactamase-catalysed hydrolysis is the primary form of β-lactam antibiotic resistance in Gram-negative bacteria. The penicillanic acid sulfone (PAS) enmetazobactam is thought to inhibit extended-spectrum β-lactamases (ESBLs) by fragmentation of an initial acyl-enzyme to form an active-site lysinoalanine cross link. We investigate interactions of enmetazobactam and its congener tazobactam with GES-1, an ESBL with structural features of carbapenem-hydrolysing β-lactamases. Crystal structures show different breakdown products of the two inhibitors covalently bound to the catalytic Ser70, assigned using quantum mechanics/molecular mechanics (QM/MM) calculations. We find no evidence for lysinoalanine formation, with mass spectrometry indicating active enzyme regeneration, behaviour previously observed for carbapenem-hydrolysing enzymes, but not ESBLs. This work establishes that PAS inhibitors interact with diverse β-lactamases by differing mechanisms, which should inform development of future compounds.
|
Sep 2025
|
|
I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Joseph F.
Hoff
,
Kirsty E.
Goudar
,
Karina
Calvopina
,
Michael
Beer
,
Philip
Hinchliffe
,
John M.
Shaw
,
Catherine L.
Tooke
,
Yuiko
Takebayashi
,
Andrew F.
Cadzow
,
Nicholas
Harmer
,
Adrian J.
Mulholland
,
Christopher J.
Schofield
,
James
Spencer
Diamond Proposal Number(s):
[23269, 31440]
Open Access
Abstract: Carbapenemases, β-lactamases hydrolysing carbapenem antibiotics, challenge treatment of multi-drug resistant bacteria. The OXA-48 carbapenemase is widely disseminated in Enterobacterales, necessitating new treatments for producer strains. Diazabicyclooctane (DBO) inhibitors, including avibactam and nacubactam, act on a wide range of enzymes to overcome β-lactamase-mediated resistance. Here we investigate avibactam and nacubactam activities towards OXA-48 and two variants, OXA-163 and OXA-405, with deletions in the β5 – β6 loop neighbouring the active site that modify activity towards different β-lactam classes. Nacubactam is c. 80-fold less potent than avibactam towards OXA-48, but this difference reduces in OXA-163 and OXA-405. Crystal structures and molecular dynamics simulations reveal electrostatic repulsion between Arg214 on the OXA-48 β5 – β6 active-site loop and nacubactam, but not avibactam, effects absent from simulations of OXA-163 and OXA-405, which lack Arg214. Crystallographic and mass spectrometry data demonstrate that all three enzymes support desulfation of bound DBOs. These data indicate that interactions with Arg214 affect DBO potency, suggesting that sequence variation in OXA-48-like β-lactamases affects reactivity towards inhibitors as well as β-lactam substrates.
|
Aug 2025
|
|
I24-Microfocus Macromolecular Crystallography
|
S. Joe
Russell
,
Catherine R.
Back
,
Christopher
Perry
,
Kaiman A.
Cheung
,
Laurence
Maschio
,
Sacha N.
Charlton
,
Nicholas R.
Lees
,
Monserrat
Manzo-Ruiz
,
Martin A.
Hayes
,
Marc W.
Van Der Kamp
,
Paul R.
Race
,
Christine L.
Willis
Diamond Proposal Number(s):
[23269]
Open Access
Abstract: The tetrodecamycins are tetracyclic natural products that exhibit potent antimicrobial activity against a multitude of drug-resistant pathogens. These compounds are structurally distinguished by the presence of a tetronate ring and trans-decalin with six contiguous asymmetric centres united by a seven-membered oxygen heterocycle. Herein we describe the first total synthesis of the antibiotic (−)-13-deoxytetrodecamycin. Our strategy is predicated on an enantioselective [4 + 2]-cycloaddition catalysed by the FAD-dependent Diels–Alderase TedJ, forming the trans-decalin with concomitant creation of two rings and four contiguous stereocenters with exquisite selectivity under mild conditions. In complementary studies, in vitro enzyme assays, X-ray crystallography and computational modelling are used to provide molecular insights into the TedJ catalysed reaction. These studies illustrate the power of adopting a chemoenzymatic approach for the enantioselective synthesis of a target compound which would be difficult to achieve using non-biological methods and provide a practical demonstration of the use of Diels–Alder biocatalysts in total synthesis. This approach has potentially widespread value in the global challenge of discovery and development of new antibiotics.
|
Aug 2025
|
|
