I03-Macromolecular Crystallography
|
Open Access
Abstract: The essential L,D-transpeptidase of Mycobacterium tuberculosis (LdtMt2) catalyses the formation of 33 cross-links in cell wall peptidoglycan and is a target for development of antituberculosis therapeutics. Efforts to inhibit LdtMt2 have been hampered by lack of knowledge of how it binds its substrate. To address this gap, we optimised the isolation of natural disaccharide tetrapeptide monomers from the Corynebacterium jeikeium bacterial cell wall through overproduction of the peptidoglycan sacculus. The tetrapeptides were used in binding / turnover assays and biophysical studies on LdtMt2. We determined a crystal structure of wild-type LdtMt2 reacted with its natural substrate, the tetrapeptide monomer of the peptidoglycan layer. This structure shows formation of a thioester linking the catalytic cysteine and the donor substrate, reflecting an intermediate in the transpeptidase reaction; it informs on the mode of entrance of the donor substrate into the LdtMt2 active site. The results will be useful in design of LdtMt2 inhibitors, including those based on substrate binding interactions, a strategy successfully employed for other nucleophilic cysteine enzymes.
|
Sep 2024
|
|
I03-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Diamond Proposal Number(s):
[17212, 23269]
Open Access
Abstract: L1 is a dizinc subclass B3 metallo-β-lactamase (MBL) that hydrolyzes most β-lactam antibiotics and is a key resistance determinant in the Gram-negative pathogen Stenotrophomonas maltophilia, an important cause of nosocomial infections in immunocompromised patients. L1 is not usefully inhibited by MBL inhibitors in clinical trials, underlying the need for further studies on L1 structure and mechanism. We describe kinetic studies and crystal structures of L1 in complex with hydrolyzed β-lactams from the penam (mecillinam), cephem (cefoxitin/cefmetazole) and carbapenem (tebipenem, doripenem and panipenem) classes. Despite differences in their structures, all the β-lactam-derived products hydrogen bond to Tyr33, Ser221 and Ser225 and are stabilized by interactions with a conserved hydrophobic pocket. The carbapenem products were modelled as Δ1-imines, with (2S)-stereochemistry. Their binding mode is determined by the presence of a 1β-methyl substituent: the Zn-bridging hydroxide either interacts with the C-6 hydroxyethyl group (1β-hydrogen-containing carbapenems), or is displaced by the C-6 carboxylate (1β-methyl-containing carbapenems). Unexpectedly, the mecillinam product is a rearranged N-formyl amide rather than penicilloic acid, with the N-formyl oxygen interacting with the Zn-bridging hydroxide. NMR studies imply mecillinam rearrangement can occur non-enzymatically in solution. Cephem-derived imine products are bound with (3R)-stereochemistry and retain their 3’ leaving groups, likely representing stable endpoints, rather than intermediates, in MBL-catalyzed hydrolysis. Our structures show preferential complex formation by carbapenem- and cephem-derived species protonated on the equivalent (β) faces, and so identify interactions that stabilize diverse hydrolyzed antibiotics. These results may be exploited in developing antibiotics, and β-lactamase inhibitors, that form long-lasting complexes with dizinc MBLs.
|
Mar 2023
|
|
I03-Macromolecular Crystallography
|
Xiao
Liu
,
Raphael
Reinbold
,
Shuang
Liu
,
Ryan A.
Herold
,
Patrick
Rabe
,
Stéphanie
Duclos
,
Rahul B.
Yadav
,
Martine I.
Abboud
,
Sandrine
Thieffine
,
Fraser A.
Armstrong
,
Lennart
Brewitz
,
Christopher J.
Schofield
Diamond Proposal Number(s):
[23459]
Open Access
Abstract: Variants of isocitrate dehydrogenase (IDH) 1 and 2 (IDH1/2) alter metabolism in cancer cells by catalyzing the NADPH-dependent reduction of 2-oxoglutate (2OG) to (2R)-hydroxyglutarate (2HG). However, it is unclear how derivatives of 2OG can affect cancer cell metabolism. Here, we used synthetic C3 and C4 alkylated 2OG derivatives to investigate the substrate selectivities of the most common cancer-associated IDH1 variant (R132H IDH1), of two cancer-associated IDH2 variants (R172K IDH2, R140Q IDH2), and of wildtype IDH1/2. Absorbance-based, NMR and electrochemical assays were employed to monitor wildtype IDH1/2 and IDH1/2 variant-catalyzed 2OG derivative turnover in the presence and absence of 2OG. Our results reveal that 2OG derivatives can serve as substrates of the investigated IDH1/2 variants, but not of wildtype IDH1/2, and have the potential to act as 2OG-competitive inhibitors. Kinetic parameters reveal that some 2OG derivatives, including the natural product 3-methyl-2OG, are equally or even more efficient IDH1/2 variant substrates compared to 2OG. Furthermore, NMR and mass spectrometry studies confirmed IDH1/2 variant-catalyzed production of alcohols in the cases of the 3-methyl-, 3-butyl-, and 3-benzyl-substituted 2OG derivatives; a crystal structure of 3-butyl-2OG with an IDH1 variant (R132C/S280F IDH1) reveals active site binding. The combined results highlight the potential for (i) IDH1/2 variant-catalyzed reduction of 2-oxoacids other than 2OG in cells, (ii) modulation of IDH1/2 variant activity by 2-oxoacid natural products, including some present in common foods, (iii) inhibition of IDH1/2 variants via active site binding rather than the established allosteric mode of inhibition, and (iv) possible use of IDH1/2 variants as biocatalysts.
|
Jan 2023
|
|
I03-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Raphael
Reinbold
,
Ingvild C.
Hvinden
,
Patrick
Rabe
,
Ryan A.
Herold
,
Alina
Finch
,
James
Wood
,
Melissa
Morgan
,
Maximillian
Staudt
,
Ian J.
Clifton
,
Fraser A.
Armstrong
,
James S. O.
Mccullagh
,
Jo
Redmond
,
Chiara
Bardella
,
Martine I.
Abboud
,
Christopher J.
Schofield
Diamond Proposal Number(s):
[23459]
Open Access
Abstract: Ivosidenib, an inhibitor of isocitrate dehydrogenase 1 (IDH1) R132C and R132H variants, is approved for the treatment of acute myeloid leukaemia (AML). Resistance to ivosidenib due to a second site mutation of IDH1 R132C, leading to IDH1 R132C/S280F, has emerged. We describe biochemical, crystallographic, and cellular studies on the IDH1 R132C/S280F and R132H/S280F variants that inform on the mechanism of second-site resistance, which involves both modulation of inhibitor binding at the IDH1 dimer-interface and alteration of kinetic properties, which enable more efficient 2-HG production relative to IDH1 R132C and IDH1 R132H. Importantly, the biochemical and cellular results demonstrate that it should be possible to overcome S280F mediated resistance in AML patients by using alternative inhibitors, including some presently in phase 2 clinical trials.
|
Aug 2022
|
|
I03-Macromolecular Crystallography
|
Patrick
Rabe
,
Carla C.
Walla
,
Noelle K.
Goodyear
,
Jordan
Welsh
,
Rebecca
Southwart
,
Ian
Clifton
,
James D. S.
Linyard
,
Anthony
Tumber
,
Tim D. W.
Claridge
,
William K.
Myers
,
Christopher J.
Schofield
Diamond Proposal Number(s):
[23459]
Open Access
Abstract: Isopenicillin N synthase (IPNS) catalyses formation of the β-lactam and thiazolidine rings of isopenicillin N (IPN) from its linear tripeptide L-δ-(α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) substrate in an iron and dioxygen (O2) dependent four electron oxidation without precedent in current synthetic chemistry. Recent X-ray free electron laser (XFEL) studies including time-resolved serial femtosecond crystallography show binding of O2 to the IPNS:Fe(II):ACV complex induces unexpected conformational changes in α-helices on the surface of IPNS, in particular in α3 and α10. However, how substrate binding leads to conformational changes away from the active site is unknown. Here, using detailed 19F NMR and EPR experiments with labelled IPNS variants, we investigated motions in α3 and α10 induced by binding of ferrous iron, ACV and the O2 analogue NO, using the less mobile α6 for comparison. 19F NMR studies were carried out on singly and doubly labelled α3, α6 and α10 variants at different temperatures. In addition, double electron-electron resonance (DEER) EPR analysis was carried out on doubly spin labelled variants. The combined spectroscopic and crystallographic results reveal that substantial conformational changes in regions of IPNS including α3 and α10 are induced by binding of ACV and NO. Since IPNS is a member of the structural superfamily of 2-oxoglutarate dependent oxygenases and related enzymes, related conformational changes may be of general importance in non-heme oxygenase catalysis.
|
Jul 2022
|
|
I03-Macromolecular Crystallography
|
Diamond Proposal Number(s):
[19458, 23459]
Open Access
Abstract: β-Lactams are the most important class of antibacterials, but their use is increasingly compromised by resistance, most importantly via serine β-lactamase (SBL)-catalyzed hydrolysis. The scope of β-lactam antibacterial activity can be substantially extended by coadministration with a penicillin-derived SBL inhibitor (SBLi), i.e., the penam sulfones tazobactam and sulbactam, which are mechanism-based inhibitors working by acylation of the nucleophilic serine. The new SBLi enmetazobactam, an N-methylated tazobactam derivative, has recently completed clinical trials. Biophysical studies on the mechanism of SBL inhibition by enmetazobactam reveal that it inhibits representatives of all SBL classes without undergoing substantial scaffold fragmentation, a finding that contrasts with previous reports on SBL inhibition by tazobactam and sulbactam. We therefore reinvestigated the mechanisms of tazobactam and sulbactam using mass spectrometry under denaturing and nondenaturing conditions, X-ray crystallography, and NMR spectroscopy. The results imply that the reported extensive fragmentation of penam sulfone–derived acyl–enzyme complexes does not substantially contribute to SBL inhibition. In addition to observation of previously identified inhibitor-induced SBL modifications, the results reveal that prolonged reaction of penam sulfones with SBLs can induce dehydration of the nucleophilic serine to give a dehydroalanine residue that undergoes reaction to give a previously unobserved lysinoalanine cross-link. The results clarify the mechanisms of action of widely clinically used SBLi, reveal limitations on the interpretation of mass spectrometry studies concerning mechanisms of SBLi, and will inform the development of new SBLi working by reaction to form hydrolytically stable acyl–enzyme complexes.
|
May 2022
|
|
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
I24-Microfocus Macromolecular Crystallography
|
Patrick
Rabe
,
Jos J. A. G.
Kamps
,
Kyle D.
Sutherlin
,
James D. S.
Linyard
,
Pierre
Aller
,
Cindy C.
Pham
,
Mikako
Makita
,
Ian
Clifton
,
Michael A.
Mcdonough
,
Thomas M.
Leissing
,
Denis
Shutin
,
Pauline A.
Lang
,
Agata
Butryn
,
Jurgen
Brem
,
Sheraz
Gul
,
Franklin D.
Fuller
,
In-Sik
Kim
,
Mun Hon
Cheah
,
Thomas
Fransson
,
Asmit
Bhowmick
,
Iris D.
Young
,
Lee
O'Riordan
,
Aaron S.
Brewster
,
Ilaria
Pettinati
,
Margaret
Doyle
,
Yasumasa
Joti
,
Shigeki
Owada
,
Kensuke
Tono
,
Alexander
Batyuk
,
Mark S.
Hunter
,
Roberto
Alonso-Mori
,
Uwe
Bergmann
,
Robin L.
Owen
,
Nicholas K.
Sauter
,
Timothy D. W.
Claridge
,
Carol V.
Robinson
,
Vittal K.
Yachandra
,
Junko
Yano
,
Jan F.
Kern
,
Allen M.
Orville
,
Christopher J.
Schofield
Diamond Proposal Number(s):
[23459, 19458]
Open Access
Abstract: Isopenicillin N synthase (IPNS) catalyzes the unique reaction of L-δ-(α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) with dioxygen giving isopenicillin N (IPN), the precursor of all natural penicillins and cephalosporins. X-ray free-electron laser studies including time-resolved crystallography and emission spectroscopy reveal how reaction of IPNS:Fe(II):ACV with dioxygen to yield an Fe(III) superoxide causes differences in active site volume and unexpected conformational changes that propagate to structurally remote regions. Combined with solution studies, the results reveal the importance of protein dynamics in regulating intermediate conformations during conversion of ACV to IPN. The results have implications for catalysis by multiple IPNS-related oxygenases, including those involved in the human hypoxic response, and highlight the power of serial femtosecond crystallography to provide insight into long-range enzyme dynamics during reactions presently impossible for nonprotein catalysts.
|
Aug 2021
|
|
I24-Microfocus Macromolecular Crystallography
|
Agata
Butryn
,
Philipp S.
Simon
,
Pierre
Aller
,
Philip
Hinchliffe
,
Ramzi N.
Massad
,
Gabriel
Leen
,
Catherine L.
Tooke
,
Isabel
Bogacz
,
In-Sik
Kim
,
Asmit
Bhowmick
,
Aaron S.
Brewster
,
Nicholas E.
Devenish
,
Jurgen
Brem
,
Jos J. A. G.
Kamps
,
Pauline A.
Lang
,
Patrick
Rabe
,
Danny
Axford
,
John H.
Beale
,
Bradley
Davy
,
Ali
Ebrahim
,
Julien
Orlans
,
Selina L. S.
Storm
,
Tiankun
Zhou
,
Shigeki
Owada
,
Rie
Tanaka
,
Kensuke
Tono
,
Gwyndaf
Evans
,
Robin L.
Owen
,
Frances A.
Houle
,
Nicholas K.
Sauter
,
Christopher J.
Schofield
,
James
Spencer
,
Vittal K.
Yachandra
,
Junko
Yano
,
Jan F.
Kern
,
Allen M.
Orville
Diamond Proposal Number(s):
[19458, 25260]
Open Access
Abstract: Serial femtosecond crystallography has opened up many new opportunities in structural biology. In recent years, several approaches employing light-inducible systems have emerged to enable time-resolved experiments that reveal protein dynamics at high atomic and temporal resolutions. However, very few enzymes are light-dependent, whereas macromolecules requiring ligand diffusion into an active site are ubiquitous. In this work we present a drop-on-drop sample delivery system that enables the study of enzyme-catalyzed reactions in microcrystal slurries. The system delivers ligand solutions in bursts of multiple picoliter-sized drops on top of a larger crystal-containing drop inducing turbulent mixing and transports the mixture to the X-ray interaction region with temporal resolution. We demonstrate mixing using fluorescent dyes, numerical simulations and time-resolved serial femtosecond crystallography, which show rapid ligand diffusion through microdroplets. The drop-on-drop method has the potential to be widely applicable to serial crystallography studies, particularly of enzyme reactions with small molecule substrates.
|
Jul 2021
|
|
I24-Microfocus Macromolecular Crystallography
|
Diamond Proposal Number(s):
[12346]
Open Access
Abstract: Metallo-β-lactamases (MBLs) can efficiently catalyze the hydrolysis of all classes of β-lactam antibiotics except monobactams. While serine-β-lactamase (SBL) inhibitors (e.g., clavulanic acid, avibactam) are established for clinical use, no such MBL inhibitors are available. We report on the synthesis and mechanism of inhibition of N-sulfamoylpyrrole-2-carboxylates (NSPCs) which are potent inhibitors of clinically relevant B1 subclass MBLs, including NDM-1. Crystallography reveals that the N-sulfamoyl NH2 group displaces the dizinc bridging hydroxide/water of the B1 MBLs. Comparison of crystal structures of an NSPC and taniborbactam (VRNX-5133), presently in Phase III clinical trials, shows similar binding modes for the NSPC and the cyclic boronate ring systems. The presence of an NSPC restores meropenem efficacy in clinically derived E. coli and K. pneumoniae blaNDM-1. The results support the potential of NSPCs and related compounds as efficient MBL inhibitors, though further optimization is required for their clinical development.
|
May 2021
|
|
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
|
Anka
Lucic
,
Philip
Hinchliffe
,
Tika R.
Malla
,
Catherine L.
Tooke
,
Jurgen
Brem
,
Karina
Calvopina
,
Christopher T.
Lohans
,
Patrick
Rabe
,
Michael A.
Mcdonough
,
Timothy
Armistead
,
Allen M.
Orville
,
James
Spencer
,
Christopher J.
Schofield
Diamond Proposal Number(s):
[17212, 23269, 18069]
Abstract: Penems have demonstrated potential as antibacterials and β-lactamase inhibitors; however, their clinical use has been limited, especially in comparison with the structurally related carbapenems. Faropenem is an orally active antibiotic with a C2 tetrahydrofuran (THF) ring, which is resistant to hydrolysis by some β-lactamases. We report studies on the reactions of faropenem with carbapenem-hydrolysing β-lactamases, focusing on the class A serine β-lactamase KPC-2 and the metallo β-lactamases (MBLs) VIM-2 (a subclass B1 MBL) and L1 (a B3 MBL). Kinetic studies show that faropenem is a substrate for all three β-lactamases, though it is less efficiently hydrolysed by KPC-2. Crystallographic analyses on faropenem-derived complexes reveal the opening of the β-lactam ring with formation of an imine with KPC-2, VIM-2, and L1. In the cases of the KPC-2 and VIM-2 structures, the THF ring is opened to give an alkene, but with L1 the THF ring remains intact. Solution state studies, employing NMR, were performed on L1, KPC-2, VIM-2, VIM-1, NDM-1, OXA-23, OXA-10, and OXA-48. The solution results reveal, in all cases, formation of imine products in which the THF ring is opened; formation of a THF ring-closed imine product was only observed with VIM-1 and VIM-2. An enamine product with a closed THF ring was also observed in all cases, at varying levels. Combined with previous reports, the results exemplify the potential for different outcomes in the reactions of penems with MBLs and SBLs and imply further structure-activity relationship studies are worthwhile to optimise the interactions of penems with β-lactamases. They also exemplify how crystal structures of β-lactamase substrate/inhibitor complexes do not always reflect reaction outcomes in solution.
|
Feb 2021
|
|
