I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[1223]
Open Access
Abstract: Protein O-GlcNAcylation is an essential reversible posttranslational modification in higher eukaryotes. O-GlcNAc addition and removal is catalyzed by O-GlcNAc transferase and O-GlcNAcase, respectively. We report the molecular details of the interaction of a bacterial O-GlcNAcase homolog with three different synthetic glycopeptides derived from characterized O-GlcNAc sites in the human proteome. Strikingly, the peptides bind a conserved O-GlcNAcase substrate binding groove with similar orientation and conformation. In addition to extensive contacts with the sugar, O-GlcNAcase recognizes the peptide backbone through hydrophobic interactions and intramolecular hydrogen bonds, while avoiding interactions with the glycopeptide side chains. These findings elucidate the molecular basis of O-GlcNAcase substrate specificity, explaining how a single enzyme achieves cycling of the complete O-GlcNAc proteome. In addition, this work will aid development of O-GlcNAcase inhibitors that target the peptide binding site.
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Feb 2012
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[8268]
Open Access
Abstract: Inhibitors of OGT (O-GlcNAc transferase) are valuable tools to study the cell biology of protein O-GlcNAcylation. We report OGT bisubstrate-linked inhibitors (goblins) in which the acceptor serine in the peptide VTPVSTA is covalently linked to UDP, eliminating the GlcNAc pyranoside ring. Goblin1 co-crystallizes with OGT, revealing an ordered C3 linker and retained substrate-binding modes, and binds the enzyme with micromolar affinity, inhibiting glycosyltransfer on to protein and peptide substrates.
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Feb 2014
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Abstract: O-GlcNAc transferase (OGT) glycosylates a diverse range of intracellular proteins with O-linked N-acetylglucosamine (O-GlcNAc), an essential and dynamic post-translational modification in metazoans. Although this enzyme modifies hundreds of proteins with O-GlcNAc, it is not understood how OGT achieves substrate specificity. In this study, we describe the application of a high-throughput OGT assay to a library of peptides. We mapped sites of O-GlcNAc modification by electron transfer dissociation MS and found that they correlate with previously detected O-GlcNAc sites. Crystal structures of four acceptor peptides in complex with Homo sapiens OGT suggest that a combination of size and conformational restriction defines sequence specificity in the −3 to +2 subsites. This work reveals that although the N-terminal TPR repeats of OGT may have roles in substrate recognition, the sequence restriction imposed by the peptide-binding site makes a substantial contribution to O-GlcNAc site specificity.
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Oct 2015
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Abstract: Erythropoietin-producing human hepatocellular carcinoma (Eph) receptor tyrosine kinases (RTKs) regulate a variety of dynamic cellular events, including cell protrusion, migration, proliferation, and cell-fate determination. Small-molecule inhibitors of Eph kinases are valuable tools for dissecting the physiological and pathological roles of Eph. However, there is a lack of small-molecule inhibitors that are selective for individual Eph isoforms due to the high homology within the family. Herein, we report the development of the first potent and specific inhibitors of a single Eph isoform, EphB3. Through structural bioinformatic analysis, we identified a cysteine in the hinge region of the EphB3 kinase domain, a feature that is not shared with any other human kinases. We synthesized and characterized a series of electrophilic quinazolines to target this unique, reactive feature in EphB3. Some of the electrophilic quinazolines selectively and potently inhibited EphB3 both in vitro and in cells. Cocrystal structures of EphB3 in complex with two quinazolines confirmed the covalent linkage between the protein and the inhibitors. A “clickable” version of an optimized inhibitor was created and employed to verify specific target engagement in the whole proteome and to probe the extent and kinetics of target engagement of existing EphB3 inhibitors. Furthermore, we demonstrate that the autophosphorylation of EphB3 within the juxtamembrane region occurs in trans using a specific inhibitor. These exquisitely specific inhibitors will facilitate the dissection of EphB3’s role in various biological processes and disease contribution.
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Aug 2016
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I02-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Abstract: Although a previously developed bump-hole approach has proven powerful in generating specific inhibitors for mapping functions of protein kinases, its application is limited by the intolerance of the large-to-small mutation by certain kinases and the inability to control two kinases separately in the same cells. Herein, we describe the development of an alternative chemical-genetic approach to overcome these limitations. Our approach features the use of an engineered cysteine residue at a particular position as a reactive feature to sensitize a kinase of interest to selective covalent blockade by electrophilic inhibitors and is thus termed Ele-Cys approach. We successfully applied the Ele-Cys approach to identify selective covalent inhibitors of a receptor tyrosine kinase EphB1, and solved cocrystal structures to determine the mode of covalent binding. Importantly, the Ele-Cys and bump-hole approaches afforded orthogonal inhibition of two distinct kinases in the cell, opening the door to their combined use in the study of multi-kinase signaling pathways.
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May 2017
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I02-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Jason G.
Kettle
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Rana
Anjum
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Evan
Barry
,
Deepa
Bhavsar
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Crystal
Brown
,
Scott
Boyd
,
Andrew
Campbell
,
Kristin
Goldberg
,
Michael
Grondine
,
Sylvie
Guichard
,
Christopher J.
Hardy
,
Tom
Hunt
,
Rhys D. O.
Jones
,
Xiuwei
Li
,
Olga
Moleva
,
Derek
Ogg
,
Ross C.
Overman
,
Martin J.
Packer
,
Stuart
Pearson
,
Marianne
Schimpl
,
Wenlin
Shao
,
Aaron
Smith
,
James M.
Smith
,
Darren
Stead
,
Steve
Stokes
,
Michael
Tucker
,
Yang
Ye
Diamond Proposal Number(s):
[12419, 14631]
Abstract: While the treatment of gastrointestinal stromal tumors (GISTs) has been revolutionized by the application of targeted tyrosine kinase inhibitors capable of inhibiting KIT-driven proliferation, diverse mutations to this kinase drive resistance to established therapies. Here we describe the identification of potent pan-KIT mutant kinase inhibitors that can be dosed without being limited by the tolerability issues seen with multitargeted agents. This effort focused on identification and optimization of an existing kinase scaffold through the use of structure-based design. Starting from a series of previously reported phenoxyquinazoline and quinoline based inhibitors of the tyrosine kinase PDGFRα, potency against a diverse panel of mutant KIT driven Ba/F3 cell lines was optimized, with a particular focus on reducing activity against a KDR driven cell model in order to limit the potential for hypertension commonly seen in second and third line GIST therapies. AZD3229 demonstrates potent single digit nM growth inhibition across a broad cell panel, with good margin to KDR-driven effects. Selectivity over KDR can be rationalized predominantly by the interaction of water molecules with the protein and ligand in the active site, and its kinome selectivity is similar to the best of the approved GIST agents. This compound demonstrates excellent cross-species pharmacokinetics, shows strong pharmacodynamic inhibition of target, and is active in several in vivo models of GIST.
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Sep 2018
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I03-Macromolecular Crystallography
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Frederick Woolf
Goldberg
,
M. Raymond V.
Finlay
,
Attilla
Ting
,
David
Beattie
,
Gillian
Lamont
,
Charlene
Fallan
,
Gail
Wrigley
,
Marianne
Schimpl
,
Martin R.
Howard
,
Beth
Williamson
,
Mercedes
Vazquez-Chantada
,
Derek
Barratt
,
Barry
Davies
,
Elaine
Cadogan
,
Antonio
Ramos Montoya
,
Emma
Dean
Abstract: DNA-PK is a key component within the DNA damage response, as it is responsible for recognizing and repairing double-strand DNA breaks (DSBs) via non-homologous end joining. Historically it has been challenging to identify inhibitors of the DNA-PK catalytic subunit (DNA-PKcs) with good selectivity versus the structurally related PI3 (lipid) and PI3K-related protein kinases. We screened our corporate collection for DNA-PKcs inhibitors with good PI3 kinase selectivity, identifying compound 1. Optimization focused on further improving selectivity whilst improving physical and pharmacokinetic properties, notably co-optimization of permeability and metabolic stability, to identify compound 16 (AZD7648). Compound 16 had no significant off-targets in the protein kinome, and only weak activity versus PI3Kα/γ lipid kinases. Monotherapy activity in murine xenograft models was observed, and regressions were observed when combined with inducers of DSBs (doxorubicin or irradiation) or PARP inhibition (olaparib). These data support progression into clinical studies (NCT03907969).
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Dec 2019
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Kirsten
Mcaulay
,
Emily A.
Hoyt
,
Morgan
Thomas
,
Marianne
Schimpl
,
Michael S.
Bodnarchuk
,
Hilary J.
Lewis
,
Derek
Barratt
,
Deepa
Bhavsar
,
David M.
Robinson
,
Michael J.
Deery
,
Derek
Ogg
,
Gonçalo J. I.
Bernardes
,
Richard A.
Ward
,
Michael J.
Waring
,
Jason G.
Kettle
Diamond Proposal Number(s):
[12419, 20015]
Abstract: With a resurgence in interest in covalent drugs, there is need to identify new moieties capable of cysteine bond formation that are differentiated from commonly employed systems such as acrylamide. Herein, we report on the discovery of new alkynyl benzoxazine and dihydroquinazoline moieties capable of covalent reaction with cysteine. Their utility as alternative electrophilic warheads for chemical biological probes and drug molecules is demonstrated through site-selective protein modification and incorporation into kinase drug scaffolds. A potent covalent inhibitor of JAK3 kinase was identified with superior selectivity across the kinome and improvements in in vitro pharmacokinetic profile relative to the related acrylamide-based inhibitor. In addition, the use of a novel heterocycle as cysteine reactive warhead is employed to target Cys788 in c-KIT where acrylamide has previously failed to form covalent interactions. These new reactive and selective heterocyclic warheads supplement the current repertoire for cysteine covalent modification whilst avoiding some of the limitations generally associated with established moieties.
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May 2020
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[14631, 17180, 20015]
Open Access
Abstract: The activation loop (A-loop) plays a key role in regulating the catalytic activity of protein kinases. Phosphorylation in this region enhances the phosphoryl transfer rate of the kinase domain and increases its affinity for ATP. Furthermore, the A-loop possesses autoinhibitory functions in some kinases, where it collapses onto the protein surface and blocks substrate binding when unphosphorylated. Due to its flexible nature, the A-loop is usually disordered and untraceable in kinase domain crystal structures. The resulting lack of structural information is regrettable as it impedes the design of drug A-loop contacts, which have proven favourable in multiple cases. Here we characterize the binding with A-loop engagement between type 1.5 kinase inhibitor ‘example 172’ (EX172) and Mer tyrosine kinase (MerTK). With the help of crystal structures and binding kinetics we portray how the recruitment of the A-loop elicits a two-step binding mechanism which results in a drug-target complex characterized by high affinity and long residence time. In addition, the type 1.5 compound possesses excellent kinome selectivity and a remarkable preference for the phosphorylated over the dephosphorylated form of MerTK. We discuss these unique characteristics in the context of known type 1 and type 2 inhibitors and highlight opportunities for future kinase inhibitor design.
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Oct 2020
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I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[17180]
Open Access
Abstract: Helicobacter pylori (H. pylori) uses several outer membrane proteins for adhering to its host's gastric mucosa, an important step in establishing and preserving colonization. Several adhesins (SabA, BabA, HopQ) have been characterized in terms of their three-dimensional structure. A recent addition to the growing list of outer membrane porins is LabA (LacdiNAc-binding adhesin), which is thought to bind specifically to GalNAcβ1-4GlcNAc, occurring in the gastric mucosa. LabA47-496 protein expressed as His-tagged protein in the periplasm of E. coli and purified via subtractive IMAC after TEV cleavage and subsequent size exclusion chromatography, resulted in bipyramidal crystals with good diffraction properties. Here, we describe the 2.06 Å resolution structure of the exodomain of LabA from H. pylori strain J99 (PDB ID: 6GMM). Strikingly, despite the relatively low levels of sequence identity with the other three structurally characterized adhesins (20–49%), LabA shares an L-shaped fold with SabA and BabA. The ‘head’ region contains a 4 + 3 α-helix bundle, with a small insertion domain consisting of a short antiparallel beta sheet and an unstructured region, not resolved in the crystal structure. Sequence alignment of LabA from different strains shows a high level of conservation in the N- and C-termini, and identifies two main types based on the length of the insertion domain (‘crown’ region), the ‘J99-type’ (insertion ~31 amino acids), and the H. pylori ‘26695 type’ (insertion ~46 amino acids). Analysis of ligand binding using Native Electrospray Ionization Mass Spectrometry (ESI-MS) together with solid phase-bound, ELISA-type assays could not confirm the originally described binding of GalNAcβ1-4GlcNAc-containing oligosaccharides, in line with other recent reports, which also failed to confirm LacdiNAc binding.
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Dec 2020
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