I23-Long wavelength MX
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Open Access
Abstract: More than a third of all known proteins bind metal ions. Metal ions play key roles in a broad range of cellular processes, they are involved in protein structure stability and catalysis; with traditional examples of zinc fingers in transcription factors and iron in haemoglobin. Therefore, identifying metal ion-binding sites is important for understanding the biological functions of proteins and further helps in designing potent therapeutics.
Experimental and computational methods have been developed to identify or predict metal ion ligand-binding residues. However, experimentally identifying and locating metal ions, such as calcium and potassium in protein structures can be challenging. The unique wavelength range of the macromolecular crystallography beamline I23 at Diamond Light Source allows identification and location of metal ions and lighter atoms of biological relevance (Ca, K, S, P and Cl) using X-ray anomalous scattering in crystal structure analysis.
In a typical experiment, anomalous datasets are collected at two wavelengths, above and below the ion or element absorption edge, and then processed to calculate phased anomalous Fourier difference maps. The difference in anomalous peak heights between these two datasets allows the direct identification and visualisation of the ion in the protein structure. We successfully used this method in different projects to experimentally map ions in crystal structures and some examples will be discussed.
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Mar 2025
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I23-Long wavelength MX
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Diamond Proposal Number(s):
[32794]
Open Access
Abstract: Voltage-dependent anion channel 1 (VDAC1) is a key protein in cellular metabolism and apoptosis. Here, we present a protocol to express and purify milligram amounts of recombinant VDAC1 in Escherichia coli. We detail steps for a fluorescence polarization-based high-throughput screening assay using NADH displacement, along with procedures for thermostability, fluorescence polarization, and X-ray crystallography. In this context, we demonstrate how 2-methyl-2,4-pentanediol (MPD), a crystallization reagent, interferes with VDAC1 small-molecule binding, hindering the detection of these ligands in the crystal.
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Mar 2025
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I03-Macromolecular Crystallography
I23-Long wavelength MX
I24-Microfocus Macromolecular Crystallography
Krios II-Titan Krios II at Diamond
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Audrey
Le Bas
,
Bradley R.
Clarke
,
Tanisha
Teelucksingh
,
Micah
Lee
,
Kamel
El Omari
,
Andrew M.
Giltrap
,
Stephen A.
Mcmahon
,
Hui
Liu
,
John H.
Beale
,
Vitaliy
Mykhaylyk
,
Ramona
Duman
,
Neil G.
Paterson
,
Philip N.
Ward
,
Peter J.
Harrison
,
Miriam
Weckener
,
Els
Pardon
,
Jan
Steyaert
,
Huanting
Liu
,
Andrew
Quigley
,
Benjamin G.
Davis
,
Armin
Wagner
,
Chris
Whitfield
,
James H.
Naismith
Diamond Proposal Number(s):
[33941]
Open Access
Abstract: The enterobacterial common antigen (ECA) is conserved in Gram-negative bacteria of the Enterobacterales order although its function is debated. ECA biogenesis depends on the Wzx/Wzy-dependent strategy whereby the newly synthesized lipid-linked repeat units, lipid III, are transferred across the inner membrane by the lipid III flippase WzxE. WzxE is part of the Wzx family and required in many glycan assembly systems, but an understanding of its molecular mechanism is hindered due to a lack of structural evidence. Here, we present the first X-ray structures of WzxE from Escherichia coli in complex with nanobodies. Both inward- and outward-facing conformations highlight two pairs of arginine residues that move in a reciprocal fashion, enabling flipping. One of the arginine pairs coordinated to a glutamate residue is essential for activity along with the C-terminal arginine rich tail located close to the entrance of the lumen. This work helps understand the translocation mechanism of the Wzx flippase family.
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Jan 2025
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I23-Long wavelength MX
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Open Access
Abstract: Analytical absorption corrections are employed in scaling diffraction data for highly absorbing samples, such as those used in long-wavelength crystallography, where empirical corrections pose a challenge. AnACor2.0 is an accelerated software package developed to calculate analytical absorption corrections. It accomplishes this by ray-tracing the paths of diffracted X-rays through a voxelized 3D model of the sample. Due to the computationally intensive nature of ray-tracing, the calculation of analytical absorption corrections for a given sample can be time consuming. Three experimental datasets (insulin at λ = 3.10 Å, thermolysin at λ = 3.53 Å and thaumatin at λ = 4.13 Å) were processed to investigate the effectiveness of the accelerated methods in AnACor2.0. These methods demonstrated a maximum reduction in execution time of up to 175× compared with previous methods. As a result, the absorption factor calculation for the insulin dataset can now be completed in less than 10 s. These acceleration methods combine sampling, which evaluates subsets of crystal voxels, with modifications to standard ray-tracing. The bisection method is used to find path lengths, reducing the complexity from O(n) to O(log2 n). The gridding method involves calculating a regular grid of diffraction paths and using interpolation to find an absorption correction for a specific reflection. Additionally, optimized and specifically designed CUDA implementations for NVIDIA GPUs are utilized to enhance performance. Evaluation of these methods using simulated and real datasets demonstrates that systematic sampling of the 3D model provides consistently accurate results with minimal variance across different sampling ratios. The mean difference of absorption factors from the full calculation (without sampling) is at most 2%. Additionally, the anomalous peak heights of sulfur atoms in the Fourier map show a mean difference of only 1% compared with the full calculation. This research refines and accelerates the process of analytical absorption corrections, introducing innovative sampling and computational techniques that significantly enhance efficiency while maintaining accurate results.
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Dec 2024
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I23-Long wavelength MX
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Diamond Proposal Number(s):
[29990]
Open Access
Abstract: One of the challenges for experimental structural biology in the 21st century is to see chemical reactions happen. Staphylococcus aureus (S. aureus) DNA gyrase is a type IIA topoisomerase that can create temporary double-stranded DNA breaks to regulate DNA topology. Drugs, such as gepotidacin, zoliflodacin and the quinolone moxifloxacin, can stabilize these normally transient DNA strand breaks and kill bacteria. Crystal structures of uncleaved DNA with a gepotidacin precursor (2.1 Å GSK2999423) or with doubly cleaved DNA and zoliflodacin (or with its progenitor QPT-1) have been solved in the same P61 space-group (a = b ≈ 93 Å, c ≈ 412 Å). This suggests that it may be possible to observe the two DNA cleavage steps (and two DNA-religation steps) in this P61 space-group. Here, a 2.58 Å anomalous manganese dataset in this crystal form is solved, and four previous crystal structures (1.98 Å, 2.1 Å, 2.5 Å and 2.65 Å) in this crystal form are re-refined to clarify crystal contacts. The structures clearly suggest a single moving metal mechanism—presented in an accompanying (second) paper. A previously published 2.98 Å structure of a yeast topoisomerase II, which has static disorder around a crystallographic twofold axis, was published as containing two metals at one active site. Re-refined coordinates of this 2.98 Å yeast structure are consistent with other type IIA topoisomerase structures in only having one metal ion at each of the two different active sites.
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Nov 2024
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I23-Long wavelength MX
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Open Access
Abstract: AlphaFold2 has revolutionized structural biology by offering unparalleled accuracy in predicting protein structures. Traditional methods for determining protein structures, such as X-ray crystallography and cryo-electron microscopy, are often time-consuming and resource-intensive. AlphaFold2 provides models that are valuable for molecular replacement, aiding in model building and docking into electron density or potential maps. However, despite its capabilities, models from AlphaFold2 do not consistently match the accuracy of experimentally determined structures, need to be validated experimentally and currently miss some crucial information, such as post-translational modifications, ligands and bound ions. In this paper, the advantages are explored of collecting X-ray anomalous data to identify chemical elements, such as metal ions, which are key to understanding certain structures and functions of proteins. This is achieved through methods such as calculating anomalous difference Fourier maps or refining the imaginary component of the anomalous scattering factor f′′. Anomalous data can serve as a valuable complement to the information provided by AlphaFold2 models and this is particularly significant in elucidating the roles of metal ions.
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Oct 2024
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I23-Long wavelength MX
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Yishun
Lu
,
Ramona
Duman
,
James
Beilsten-Edmands
,
Graeme
Winter
,
Mark
Basham
,
Gwyndaf
Evans
,
Jos J. A. G.
Kamps
,
Allen M.
Orville
,
Hok-Sau
Kwong
,
Konstantinos
Beis
,
Wesley
Armour
,
Armin
Wagner
Open Access
Abstract: rocessing of single-crystal X-ray diffraction data from area detectors can be separated into two steps. First, raw intensities are obtained by integration of the diffraction images, and then data correction and reduction are performed to determine structure-factor amplitudes and their uncertainties. The second step considers the diffraction geometry, sample illumination, decay, absorption and other effects. While absorption is only a minor effect in standard macromolecular crystallography (MX), it can become the largest source of uncertainty for experiments performed at long wavelengths. Current software packages for MX typically employ empirical models to correct for the effects of absorption, with the corrections determined through the procedure of minimizing the differences in intensities between symmetry-equivalent reflections; these models are well suited to capturing smoothly varying experimental effects. However, for very long wavelengths, empirical methods become an unreliable approach to model strong absorption effects with high fidelity. This problem is particularly acute when data multiplicity is low. This paper presents an analytical absorption correction strategy (implemented in new software AnACor) based on a volumetric model of the sample derived from X-ray tomography. Individual path lengths through the different sample materials for all reflections are determined by a ray-tracing method. Several approaches for absorption corrections (spherical harmonics correction, analytical absorption correction and a combination of the two) are compared for two samples, the membrane protein OmpK36 GD, measured at a wavelength of λ = 3.54 Å, and chlorite dismutase, measured at λ = 4.13 Å. Data set statistics, the peak heights in the anomalous difference Fourier maps and the success of experimental phasing are used to compare the results from the different absorption correction approaches. The strategies using the new analytical absorption correction are shown to be superior to the standard spherical harmonics corrections. While the improvements are modest in the 3.54 Å data, the analytical absorption correction outperforms spherical harmonics in the longer-wavelength data (λ = 4.13 Å), which is also reflected in the reduced amount of data being required for successful experimental phasing.
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Jun 2024
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I03-Macromolecular Crystallography
I23-Long wavelength MX
I24-Microfocus Macromolecular Crystallography
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Tomas
Malinauskas
,
Gareth
Moore
,
Amalie F.
Rudolf
,
Holly
Eggington
,
Hayley L.
Belnoue-Davis
,
Kamel
El Omari
,
Samuel C.
Griffiths
,
Rachel E.
Woolley
,
Ramona
Duman
,
Armin
Wagner
,
Simon J.
Leedham
,
Clair
Baldock
,
Hilary L.
Ashe
,
Christian
Siebold
Diamond Proposal Number(s):
[28534, 14744, 19946]
Open Access
Abstract: Twisted gastrulation (TWSG1) is an evolutionarily conserved secreted glycoprotein which controls signaling by Bone Morphogenetic Proteins (BMPs). TWSG1 binds BMPs and their antagonist Chordin to control BMP signaling during embryonic development, kidney regeneration and cancer. We report crystal structures of TWSG1 alone and in complex with a BMP ligand, Growth Differentiation Factor 5. TWSG1 is composed of two distinct, disulfide-rich domains. The TWSG1 N-terminal domain occupies the BMP type 1 receptor binding site on BMPs, whereas the C-terminal domain binds to a Chordin family member. We show that TWSG1 inhibits BMP function in cellular signaling assays and mouse colon organoids. This inhibitory function is abolished in a TWSG1 mutant that cannot bind BMPs. The same mutation in the Drosophila TWSG1 ortholog Tsg fails to mediate BMP gradient formation required for dorsal-ventral axis patterning of the early embryo. Our studies reveal the evolutionarily conserved mechanism of BMP signaling inhibition by TWSG1.
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Jun 2024
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B21-High Throughput SAXS
I23-Long wavelength MX
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Carlos
Vela-Rodríguez
,
Chunsong
Yang
,
Heli I.
Alanen
,
Rebeka
Eki
,
Tarek A.
Abbas
,
Mirko M.
Maksimainen
,
Tuomo
Glumoff
,
Ramona
Duman
,
Armin
Wagner
,
Bryce M.
Paschal
,
Lari
Lehtio
Diamond Proposal Number(s):
[26794]
Open Access
Abstract: Deltex proteins are a family of E3 ubiquitin ligases that encode C-terminal RING and DTC domains that mediate interactions with E2 ubiquitin-conjugating enzymes and recognize ubiquitination substrates. DTX3L is unique among the Deltex proteins based on its N-terminal domain architecture. The N-terminal D1 and D2 domains of DTX3L mediate homo-oligomerization, and the D3 domain interacts with PARP9, a protein that contains tandem macrodomains with ADP-ribose reader function. While DTX3L and PARP9 are known to heterodimerize, and assemble into a high molecular weight oligomeric complex, the nature of the oligomeric structure, including whether this contributes to the ADP-ribose reader function is unknown. Here, we report a crystal structure of the DTX3L N-terminal D2 domain and show that it forms a tetramer with, conveniently, D2 symmetry. We identified two interfaces in the structure: a major, conserved interface with a surface of 973 Å2 and a smaller one of 415 Å2. Using native mass spectrometry, we observed molecular species that correspond to monomers, dimers and tetramers of the D2 domain. Reconstitution of DTX3L knockout cells with a D1-D2 deletion mutant showed the domain is dispensable for DTX3L-PARP9 heterodimer formation, but necessary to assemble an oligomeric complex with efficient reader function for ADP-ribosylated androgen receptor. Our results suggest that homo-oligomerization of DTX3L is important for the DTX3L-PARP9 complex to read mono-ADP-ribosylation on a ligand-regulated transcription factor.
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Apr 2024
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I03-Macromolecular Crystallography
I23-Long wavelength MX
I24-Microfocus Macromolecular Crystallography
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Gergely N.
Nagy
,
Xiao-Feng
Zhao
,
Richard
Karlsson
,
Karen
Wang
,
Ramona
Duman
,
Karl
Harlos
,
Kamel
El Omari
,
Armin
Wagner
,
Henrik
Clausen
,
Rebecca L.
Miller
,
Roman J.
Giger
,
E. Yvonne
Jones
Diamond Proposal Number(s):
[19946, 28534]
Open Access
Abstract: Integration of extracellular signals by neurons is pivotal for brain development, plasticity, and repair. Axon guidance relies on receptor-ligand interactions crosstalking with extracellular matrix components. Semaphorin-5A (Sema5A) is a bifunctional guidance cue exerting attractive and inhibitory effects on neuronal growth through the interaction with heparan sulfate (HS) and chondroitin sulfate (CS) glycosaminoglycans (GAGs), respectively. Sema5A harbors seven thrombospondin type-1 repeats (TSR1-7) important for GAG binding, however the underlying molecular basis and functions in vivo remain enigmatic. Here we dissect the structural basis for Sema5A:GAG specificity and demonstrate the functional significance of this interaction in vivo. Using x-ray crystallography, we reveal a dimeric fold variation for TSR4 that accommodates GAG interactions. TSR4 co-crystal structures identify binding residues validated by site-directed mutagenesis. In vitro and cell-based assays uncover specific GAG epitopes necessary for TSR association. We demonstrate that HS-GAG binding is preferred over CS-GAG and mediates Sema5A oligomerization. In vivo, Sema5A:GAG interactions are necessary for Sema5A function and regulate Plexin-A2 dependent dentate progenitor cell migration. Our study rationalizes Sema5A associated developmental and neurological disorders and provides mechanistic insights into how multifaceted guidance functions of a single transmembrane cue are regulated by proteoglycans.
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Mar 2024
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