I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Sherine E.
Thomas
,
William J.
Mccarthy
,
Jamal
El Bakali
,
Karen P.
Brown
,
So Yeon
Kim
,
Michal
Blaszczyk
,
Vitor
Mendes
,
Chris
Abell
,
R. Andres
Floto
,
Anthony G.
Coyne
,
Tom L.
Blundell
Diamond Proposal Number(s):
[9537, 14043, 18548]
Open Access
Abstract: Anti-microbial resistance is a rising global healthcare concern that needs urgent attention as growing number of infections become difficult to treat with the currently available antibiotics. This is particularly true for mycobacterial infections like tuberculosis and leprosy and those with emerging opportunistic pathogens such as Mycobacterium abscessus, where multi-drug resistance leads to increased healthcare cost and mortality. M. abscessus is a highly drug-resistant non-tuberculous mycobacterium which causes life-threatening infections in people with chronic lung conditions such as cystic fibrosis. In this study, we explore M. abscessus phosphopantetheine adenylyl transferase (PPAT), an enzyme involved in the biosynthesis of Coenzyme A, as a target for the development of new antibiotics. We provide structural insights into substrate and feedback inhibitor binding modes of M. abscessus PPAT, thereby setting the basis for further chemical exploration of the enzyme. We then utilize a multi-dimensional fragment screening approach involving biophysical and structural analysis, followed by evaluation of compounds from a previous fragment-based drug discovery campaign against M. tuberculosis PPAT ortholog. This allowed the identification of an early-stage lead molecule exhibiting low micro molar affinity against M. abscessus PPAT (Kd 3.2 ± 0.8 µM) and potential new ways to design inhibitors against this enzyme. The resulting crystal structures reveal striking conformational changes and closure of solvent channel of M. abscessus PPAT hexamer providing novel strategies of inhibition. The study thus validates the ligandability of M. abscessus PPAT as an antibiotic target and identifies crucial starting points for structure-guided drug discovery against this bacterium.
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May 2022
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Sitthivut
Charoensutthivarakul
,
Sherine E.
Thomas
,
Amy
Curran
,
Karen P.
Brown
,
Juan M.
Belardinelli
,
Andrew J.
Whitehouse
,
Marta
Acebron-Garcia-De-Eulate
,
Jaspar
Sangan
,
Subramanian G.
Gramani
,
Mary
Jackson
,
Vitor
Mendes
,
R. Andres
Floto
,
Tom L.
Blundell
,
Anthony G.
Coyne
,
Chris
Abell
Diamond Proposal Number(s):
[9537, 14043, 18548]
Abstract: Mycobacterium abscessus (Mab) has emerged as a challenging threat to individuals with cystic fibrosis. Infections caused by this pathogen are often impossible to treat due to the intrinsic antibiotic resistance leading to lung malfunction and eventually death. Therefore, there is an urgent need to develop new drugs against novel targets in Mab to overcome drug resistance and subsequent treatment failure. In this study, SAICAR synthetase (PurC) from Mab was identified as a promising target for novel antibiotics. An in-house fragment library screen and a high-throughput X-ray crystallographic screen of diverse fragment libraries were explored to provide crucial starting points for fragment elaboration. A series of compounds developed from fragment growing and merging strategies, guided by crystallographic information and careful hit-to-lead optimization, have achieved potent nanomolar binding affinity against the enzyme. Some compounds also show a promising inhibitory effect against Mab and Mtb. This work utilizes a fragment-based design and demonstrates for the first time the potential to develop inhibitors against PurC from Mab.
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Jan 2022
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Marta
Acebron-Garcia-De-Eulate
,
Joan
Mayol-Llinàs
,
Matthew T. O.
Holland
,
So Yeon
Kim
,
Karen P.
Brown
,
Chiara
Marchetti
,
Jeannine
Hess
,
Ornella
Di Pietro
,
Vitor
Mendes
,
Chris
Abell
,
R. Andres
Floto
,
Anthony G.
Coyne
,
Tom L.
Blundell
Diamond Proposal Number(s):
[18548]
Abstract: Pseudomonas aeruginosa is of major concern for cystic fibrosis patients where this infection can be fatal. With the emergence of drug-resistant strains, there is an urgent need to develop novel antibiotics against P. aeruginosa. MurB is a promising target for novel antibiotic development as it is involved in the cell wall biosynthesis. MurB has been shown to be essential in P. aeruginosa, and importantly, no MurB homologue exists in eukaryotic cells. A fragment-based drug discovery approach was used to target Pa MurB. This led to the identification of a number of fragments, which were shown to bind to MurB. One fragment, a phenylpyrazole scaffold, was shown by ITC to bind with an affinity of Kd = 2.88 mM (LE 0.23). Using a structure guided approach, different substitutions were synthesized and the initial fragment was optimized to obtain a small molecule with Kd = 3.57 μM (LE 0.35).
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Jan 2022
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Pooja
Gupta
,
Sherine E.
Thomas
,
Shaymaa A.
Zaidan
,
Maria A.
Pasillas
,
James
Cory-Wright
,
Víctor
Sebastián-Pérez
,
Ailidh
Burgess
,
Emma
Cattermole
,
Clio
Meghir
,
Chris
Abell
,
Anthony G.
Coyne
,
William R.
Jacobs
,
Tom L.
Blundell
,
Sangeeta
Tiwari
,
Vitor
Mendes
Diamond Proposal Number(s):
[14043, 18548]
Open Access
Abstract: The L-arginine biosynthesis pathway consists of eight enzymes that catalyse the conversion of L-glutamate to L-arginine. Arginine auxotrophs (argB/argF deletion mutants) of Mycobacterium tuberculosis are rapidly sterilised in mice, while inhibition of ArgJ with Pranlukast was found to clear chronic M. tuberculosis infection in a mouse model. Enzymes in the arginine biosynthetic pathway have therefore emerged as promising targets for anti-tuberculosis drug discovery. In this work, the ligandability of four enzymes of the pathway ArgB, ArgC, ArgD and ArgF is assessed using a fragment-based approach. We identify several hits against these enzymes validated with biochemical and biophysical assays, as well as X-ray crystallographic data, which in the case of ArgB were further confirmed to have on-target activity against M. tuberculosis. These results demonstrate the potential for more enzymes in this pathway to be targeted with dedicated drug discovery programmes.
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Jun 2021
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
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Vitor
Mendes
,
Simon R.
Green
,
Joanna C.
Evans
,
Jeannine
Hess
,
Michael
Blaszczyk
,
Christina
Spry
,
Owain
Bryant
,
James
Cory-Wright
,
Daniel S-H.
Chan
,
Pedro H. M.
Torres
,
Zhe
Wang
,
Navid
Nahiyaan
,
Sandra
O’neill
,
Sebastian
Damerow
,
John
Post
,
Tracy
Bayliss
,
Sasha L.
Lynch
,
Anthony G.
Coyne
,
Peter C.
Ray
,
Chris
Abell
,
Kyu Y.
Rhee
,
Helena I. M.
Boshoff
,
Clifton E.
Barry
,
Valerie
Mizrahi
,
Paul G.
Wyatt
,
Tom L.
Blundell
Diamond Proposal Number(s):
[9537, 14043, 18548]
Open Access
Abstract: Coenzyme A (CoA) is a fundamental co-factor for all life, involved in numerous metabolic pathways and cellular processes, and its biosynthetic pathway has raised substantial interest as a drug target against multiple pathogens including Mycobacterium tuberculosis. The biosynthesis of CoA is performed in five steps, with the second and third steps being catalysed in the vast majority of prokaryotes, including M. tuberculosis, by a single bifunctional protein, CoaBC. Depletion of CoaBC was found to be bactericidal in M. tuberculosis. Here we report the first structure of a full-length CoaBC, from the model organism Mycobacterium smegmatis, describe how it is organised as a dodecamer and regulated by CoA thioesters. A high-throughput biochemical screen focusing on CoaB identified two inhibitors with different chemical scaffolds. Hit expansion led to the discovery of potent and selective inhibitors of M. tuberculosis CoaB, which we show to bind to a cryptic allosteric site within CoaB.
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Jan 2021
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Sherine E.
Thomas
,
Andrew J.
Whitehouse
,
Karen
Brown
,
Sophie
Burbaud
,
Juan m
Belardinelli
,
Jasper
Sangen
,
Ramanuj
Lahiri
,
Mark daben j.
Libardo
,
Pooja
Gupta
,
Sony
Malhotra
,
Helena I. M.
Boshoff
,
Mary
Jackson
,
Chris
Abell
,
Anthony g.
Coyne
,
Tom L.
Blundell
,
Rodrigo Andres
Floto
,
Vitor
Mendes
Diamond Proposal Number(s):
[9537, 14043, 18548]
Open Access
Abstract: Translational frameshift errors are often deleterious to the synthesis of functional proteins and could therefore be promoted therapeutically to kill bacteria. TrmD (tRNA-(N(1)G37) methyltransferase) is an essential tRNA modification enzyme in bacteria that prevents +1 errors in the reading frame during protein translation and represents an attractive potential target for the development of new antibiotics. Here, we describe the application of a structure-guided fragment-based drug discovery approach to the design of a new class of inhibitors against TrmD in Mycobacterium abscessus. Fragment library screening, followed by structure-guided chemical elaboration of hits, led to the rapid development of drug-like molecules with potent in vitro TrmD inhibitory activity. Several of these compounds exhibit activity against planktonic M. abscessus and M. tuberculosis as well as against intracellular M. abscessus and M. leprae, indicating their potential as the basis for a novel class of broad-spectrum mycobacterial drugs.
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Jun 2020
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Diamond Proposal Number(s):
[9537, 14043]
Open Access
Abstract: Tuberculosis (TB) remains a leading cause of mortality amongst infectious diseases worldwide. InhA, an enoyl ACP-reductase, has been the focus of numerous drug discovery efforts as this is the target of the first line pro-drug isoniazid. However, with resistance to this drug becoming more common the aim has been to find new clinical candidates that directly inhibit this enzyme and that do not require activation by the catalase peroxidase KatG, thus circumventing the majority of the resistance mechanisms. In this work, the screening and validation of a fragment library is described and development of the fragment hits using a fragment growing strategy was employed which led to the development InhA inhibitors with affinities of up to 250 nM.
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Apr 2020
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I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[9007, 9537]
Open Access
Abstract: Trehalose is an essential disaccharide for mycobacteria and a key constituent of several cell wall glycolipids with fundamental roles in pathogenesis. Mycobacteria possess two pathways for trehalose biosynthesis. However, only the OtsAB pathway was found to be essential in Mycobacterium tuberculosis, with marked growth and virulence defects of OtsA mutants and strict essentiality of OtsB2. Here, we report the first mycobacterial OtsA structures from Mycobacterium thermoresistibile in both apo and ligand-bound forms. Structural information reveals three key residues in the mechanism of substrate preference that were further confirmed by site-directed mutagenesis. Additionally, we identify 2-oxoglutarate and 2-phosphoglycerate as allosteric regulators of OtsA. The structural analysis in this work strongly contributed to define the mechanisms for feedback inhibition, show different conformational states of the enzyme, and map a new allosteric site.
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Dec 2019
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I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Andrew J.
Whitehouse
,
Sherine E.
Thomas
,
Karen P.
Brown
,
Alexander
Fanourakis
,
Daniel S.-H.
Chan
,
M. Daben J.
Libardo
,
Vitor
Mendes
,
Helena I. M.
Boshoff
,
R. Andres
Floto
,
Chris
Abell
,
Tom
Blundell
,
Anthony G.
Coyne
Diamond Proposal Number(s):
[9537, 14043, 18548]
Open Access
Abstract: Mycobacterium abscessus (Mab) is a rapidly growing species of multidrug-resistant nontuberculous mycobacteria that has emerged as a growing threat to individuals with cystic fibrosis and other pre-existing chronic lung diseases. Mab pulmonary infections are difficult, or sometimes impossible, to treat and result in accelerated lung function decline and premature death. There is therefore an urgent need to develop novel antibiotics with improved efficacy. tRNA (m1G37) methyltransferase (TrmD) is a promising target for novel antibiotics. It is essential in Mab and other mycobacteria, improving reading frame maintenance on the ribosome to prevent frameshift errors. In this work, a fragment-based approach was employed with the merging of two fragments bound to the active site, followed by structure-guided elaboration to design potent nanomolar inhibitors against Mab TrmD. Several of these compounds exhibit promising activity against mycobacterial species, including Mycobacterium tuberculosis and Mycobacterium leprae in addition to Mab, supporting the use of TrmD as a target for the development of antimycobacterial compounds.
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Jul 2019
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
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Sherine E.
Thomas
,
Patrick
Collins
,
Rory Hennell
James
,
Vitor
Mendes
,
Sitthivut
Charoensutthivarakul
,
Chris
Radoux
,
Chris
Abell
,
Anthony G.
Coyne
,
R. Andres
Floto
,
Frank
Von Delft
,
Tom
Blundell
Open Access
Abstract: Structure-guided drug discovery emerged in the 1970s and 1980s, stimulated by the three-dimensional structures of protein targets that became available, mainly through X-ray crystal structure analysis, assisted by the development of synchrotron radiation sources. Structures of known drugs or inhibitors were used to guide the development of leads. The growth of high-throughput screening during the late 1980s and the early 1990s in the pharmaceutical industry of chemical libraries of hundreds of thousands of compounds of molecular weight of approximately 500 Da was impressive but still explored only a tiny fraction of the chemical space of the predicted 1040 drug-like compounds. The use of fragments with molecular weights less than 300 Da in drug discovery not only decreased the chemical space needing exploration but also increased promiscuity in binding targets. Here we discuss advances in X-ray fragment screening and the challenge of identifying sites where fragments not only bind but can be chemically elaborated while retaining their positions and binding modes. We first describe the analysis of fragment binding using conventional X-ray difference Fourier techniques, with Mycobacterium abscessus SAICAR synthetase (PurC) as an example. We observe that all fragments occupy positions predicted by computational hotspot mapping. We compare this with fragment screening at Diamond Synchrotron Light Source XChem facility using PanDDA software, which identifies many more fragment hits, only some of which bind to the predicted hotspots. Many low occupancy sites identified may not support elaboration to give adequate ligand affinity, although they will likely be useful in drug discovery as ‘warm spots’ for guiding elaboration of fragments bound at hotspots. We discuss implications of these observations for fragment screening at the synchrotron sources.
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Jun 2019
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