I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Open Access
Abstract: Centromeres are microtubule attachment sites on chromosomes defined by the enrichment of histone variant CENP‐A‐containing nucleosomes. To preserve centromere identity, CENP‐A must be escorted to centromeres by a CENP‐A‐specific chaperone for deposition. Despite this essential requirement, many eukaryotes differ in the composition of players involved in centromere maintenance, highlighting the plasticity of this process. In humans, CENP‐A recognition and centromere targeting are achieved by HJURP and the Mis18 complex, respectively. Using X‐ray crystallography, we here show how Drosophila CAL1, an evolutionarily distinct CENP‐A histone chaperone, binds both CENP‐A and the centromere receptor CENP‐C without the requirement for the Mis18 complex. While an N‐terminal CAL1 fragment wraps around CENP‐A/H4 through multiple physical contacts, a C‐terminal CAL1 fragment directly binds a CENP‐C cupin domain dimer. Although divergent at the primary structure level, CAL1 thus binds CENP‐A/H4 using evolutionarily conserved and adaptive structural principles. The CAL1 binding site on CENP‐C is strategically positioned near the cupin dimerisation interface, restricting binding to just one CAL1 molecule per CENP‐C dimer. Overall, by demonstrating how CAL1 binds CENP‐A/H4 and CENP‐C, we provide key insights into the minimalistic principles underlying centromere maintenance.
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Mar 2020
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[15916]
Open Access
Abstract: AMPylation is an inactivating modification that alters the activity of the major endoplasmic reticulum (ER) chaperone BiP to match the burden of unfolded proteins. A single ER‐localised Fic protein, FICD (HYPE), catalyses both AMPylation and deAMPylation of BiP. However, the basis for the switch in FICD's activity is unknown. We report on the transition of FICD from a dimeric enzyme, that deAMPylates BiP, to a monomer with potent AMPylation activity. Mutations in the dimer interface, or of residues along an inhibitory pathway linking the dimer interface to the enzyme's active site, favour BiP AMPylation in vitro and in cells. Mechanistically, monomerisation relieves a repressive effect allosterically propagated from the dimer interface to the inhibitory Glu234, thereby permitting AMPylation‐competent binding of MgATP. Moreover, a reciprocal signal, propagated from the nucleotide‐binding site, provides a mechanism for coupling the oligomeric state and enzymatic activity of FICD to the energy status of the ER.
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Sep 2019
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I02-Macromolecular Crystallography
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Ian T.
Cadby
,
Sarah M
Basford
,
Ruth
Nottingham
,
Richard
Meek
,
Rebecca
Lowry
,
Carey
Lambert
,
Matthew
Tridgett
,
Rob
Till
,
Rashidah
Ahmad
,
Rowena
Fung
,
Laura
Hobley
,
William S.
Hughes
,
Patrick J.
Moynihan
,
R. Elizabeth
Sockett
,
Andrew L.
Lovering
Open Access
Abstract: Bacterial usage of the cyclic dinucleotide c‐di‐GMP is widespread, governing the transition between motile/sessile and unicellular/multicellular behaviors. There is limited information on c‐di‐GMP metabolism, particularly on regulatory mechanisms governing control of EAL c‐di‐GMP phosphodiesterases. Herein, we provide high‐resolution structures for an EAL enzyme Bd1971, from the predatory bacterium Bdellovibrio bacteriovorus, which is controlled by a second signaling nucleotide, cAMP. The full‐length cAMP‐bound form reveals the sensory N‐terminus to be a domain‐swapped variant of the cNMP/CRP family, which in the cAMP‐activated state holds the C‐terminal EAL enzyme in a phosphodiesterase‐active conformation. Using a truncation mutant, we trap both a half‐occupied and inactive apo‐form of the protein, demonstrating a series of conformational changes that alter juxtaposition of the sensory domains. We show that Bd1971 interacts with several GGDEF proteins (c‐di‐GMP producers), but mutants of Bd1971 do not share the discrete phenotypes of GGDEF mutants, instead having an elevated level of c‐di‐GMP, suggesting that the role of Bd1971 is to moderate these levels, allowing “action potentials” to be generated by each GGDEF protein to effect their specific functions.
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Jun 2019
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Krios II-Titan Krios II at Diamond
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Open Access
Abstract: Bacteria have evolved macromolecular machineries that secrete effectors and toxins to survive and thrive in diverse environments. The type VI secretion system (T6SS) is a contractile machine that is related to Myoviridae phages. It is composed of a phage tail‐like structure inserted in the bacterial cell envelope by a membrane complex (MC) comprising the TssJ, TssL and TssM proteins. We previously reported the low‐resolution negative‐stain electron microscopy structure of the enteroaggregative Escherichia coli MC and proposed a rotational 5‐fold symmetry with a TssJ:TssL:TssM stoichiometry of 2:2:2. Here, cryo‐electron tomography analyses of the T6SS MC confirm the 5‐fold symmetry in situ and identify the regions of the structure that insert into the bacterial membranes. A high‐resolution model obtained by single‐particle cryo‐electron microscopy highlights new features: five additional copies of TssJ, yielding a TssJ:TssL:TssM stoichiometry of 3:2:2, an 11‐residue loop in TssM, protruding inside the lumen of the MC and constituting a functionally important periplasmic gate, and hinge regions. Based on these data, we propose an updated model on MC structure and dynamics during T6SS assembly and function.
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Mar 2019
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I04-Macromolecular Crystallography
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Matous
Hrdinka
,
Lisa
Schlicher
,
Bing
Dai
,
Daniel M.
Pinkas
,
Joshua C.
Bufton
,
Sarah
Picaud
,
Jennifer A.
Ward
,
Catherine
Rogers
,
Chalada
Suebsuwong
,
Sameer
Nikhar
,
Gregory D.
Cuny
,
Kilian V. M.
Huber
,
Panagis
Filippakopoulos
,
Alex N.
Bullock
,
Alexei
Degterev
,
Mads
Gyrd‐hansen
Diamond Proposal Number(s):
[15433]
Open Access
Abstract: RIPK2 mediates inflammatory signaling by the bacteria‐sensing receptors NOD1 and NOD2. Kinase inhibitors targeting RIPK2 are a proposed strategy to ameliorate NOD‐mediated pathologies. Here, we reveal that RIPK2 kinase activity is dispensable for NOD2 inflammatory signaling and show that RIPK2 inhibitors function instead by antagonizing XIAP‐binding and XIAP‐mediated ubiquitination of RIPK2. We map the XIAP binding site on RIPK2 to the loop between β2 and β3 of the N‐lobe of the kinase, which is in close proximity to the ATP‐binding pocket. Through characterization of a new series of ATP pocket‐binding RIPK2 inhibitors, we identify the molecular features that determine their inhibition of both the RIPK2‐XIAP interaction, and of cellular and in vivoNOD2 signaling. Our study exemplifies how targeting of the ATP‐binding pocket in RIPK2 can be exploited to interfere with the RIPK2‐XIAP interaction for modulation of NOD signaling.
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Jul 2018
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I02-Macromolecular Crystallography
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Kristof
Moonens
,
Youssef
Hamway
,
Matthias
Neddermann
,
Marc
Reschke
,
Nicole
Tegtmeyer
,
Tobias
Kruse
,
Robert
Kammerer
,
Raquel
Mejías‐luque
,
Bernhard B
Singer
,
Steffen
Backert
,
Markus
Gerhard
,
Han
Remaut
Diamond Proposal Number(s):
[12718]
Abstract: The human gastric pathogen Helicobacter pylori is a major causative agent of gastritis, peptic ulcer disease, and gastric cancer. As part of its adhesive lifestyle, the bacterium targets members of the carcinoembryonic antigen‐related cell adhesion molecule (CEACAM) family by the conserved outer membrane adhesin HopQ. The HopQ–CEACAM1 interaction is associated with inflammatory responses and enables the intracellular delivery and phosphorylation of the CagA oncoprotein via a yet unknown mechanism. Here, we generated crystal structures of HopQ isotypes I and II bound to the N‐terminal domain of human CEACAM1 (C1ND) and elucidated the structural basis of H. pylori specificity toward human CEACAM receptors. Both HopQ alleles target the β‐strands G, F, and C of C1ND, which form the trans dimerization interface in homo‐ and heterophilic CEACAM interactions. Using SAXS, we show that the HopQ ectodomain is sufficient to induce C1ND monomerization and thus providing H. pylori a route to influence CEACAM‐mediated cell adherence and signaling events.
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Jun 2018
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Selena G.
Burgess
,
Manjeet
Mukherjee
,
Sarah
Sabir
,
Nimesh
Joseph
,
Cristina
Gutiérrez‐caballero
,
Mark W.
Richards
,
Nicolas
Huguenin‐dezot
,
Jason W.
Chin
,
Eileen J.
Kennedy
,
Mark
Pfuhl
,
Stephen J.
Royle
,
Fanni
Gergely
,
Richard
Bayliss
Open Access
Abstract: Aurora‐A regulates the recruitment of TACC3 to the mitotic spindle through a phospho‐dependent interaction with clathrin heavy chain (CHC). Here, we describe the structural basis of these interactions, mediated by three motifs in a disordered region of TACC3. A hydrophobic docking motif binds to a previously uncharacterized pocket on Aurora‐A that is blocked in most kinases. Abrogation of the docking motif causes a delay in late mitosis, consistent with the cellular distribution of Aurora‐A complexes. Phosphorylation of Ser558 engages a conformational switch in a second motif from a disordered state, needed to bind the kinase active site, into a helical conformation. The helix extends into a third, adjacent motif that is recognized by a helical‐repeat region of CHC, not a recognized phospho‐reader domain. This potentially widespread mechanism of phospho‐recognition provides greater flexibility to tune the molecular details of the interaction than canonical recognition motifs that are dominated by phosphate binding.
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Mar 2018
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[14043]
Abstract: Myostatin, a key regulator of muscle mass in vertebrates, is biosynthesised as a latent precursor in muscle and is activated by sequential proteolysis of the pro-domain. To investigate the molecular mechanism by which pro-myostatin remains latent, we have determined the structure of unprocessed pro-myostatin and analysed the properties of the protein in its different forms. Crystal structures and SAXS analyses show that pro-myostatin adopts an open, V-shaped structure with a domain-swapped arrangement. The pro-mature complex, after cleavage of the furin site, has significantly reduced activity compared with the mature growth factor and persists as a stable complex that is resistant to the natural antagonist follistatin. The latency appears to be conferred by a number of distinct features that collectively stabilise the interaction of the pro-domains with the mature growth factor, enabling a regulated stepwise activation process, distinct from the prototypical pro-TGF-β1. These results provide a basis for understanding the effect of missense mutations in pro-myostatin and pave the way for the design of novel myostatin inhibitors.
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Jan 2018
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I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[15916]
Abstract: The Ser/Thr protein kinase PINK1 phosphorylates the well‐folded, globular protein ubiquitin (Ub) at a relatively protected site, Ser65. We previously showed that Ser65 phosphorylation results in a conformational change in which Ub adopts a dynamic equilibrium between the known, common Ub conformation and a distinct, second conformation wherein the last β‐strand is retracted to extend the Ser65 loop and shorten the C‐terminal tail. We show using chemical exchange saturation transfer (CEST) nuclear magnetic resonance experiments that a similar, C‐terminally retracted (Ub‐CR) conformation also exists at low population in wild‐type Ub. Point mutations in the moving β5 and neighbouring β‐strands shift the Ub/Ub‐CR equilibrium. This enabled functional studies of the two states, and we show that while the Ub‐CR conformation is defective for conjugation, it demonstrates improved binding to PINK1 through its extended Ser65 loop, and is a superior PINK1 substrate. Together our data suggest that PINK1 utilises a lowly populated yet more suitable Ub‐CR conformation of Ub for efficient phosphorylation. Our findings could be relevant for many kinases that phosphorylate residues in folded protein domains.
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Nov 2017
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Kiran
Bountra
,
Gregor
Hagelueken
,
Hassanul
Choudhury
,
Valentina
Corradi
,
Kamel
El Omari
,
Armin
Wagner
,
Indran
Mathavan
,
Séverine
Zirah
,
Weixiao
Yuan Wahlgren
,
D. Peter
Tieleman
,
Olav
Schiemann
,
Sylvie
Rebuffat
,
Konstantinos
Beis
Diamond Proposal Number(s):
[8031]
Open Access
Abstract: Certain pathogenic bacteria produce and release toxic peptides to ensure either nutrient availability or evasion from the immune system. These peptides are also toxic to the producing bacteria that utilize dedicated ABC transporters to provide self‐immunity. The ABC transporter McjD exports the antibacterial peptide MccJ25 in Escherichia coli. Our previously determined McjD structure provided some mechanistic insights into antibacterial peptide efflux. In this study, we have determined its structure in a novel conformation, apo inward‐occluded and a new nucleotide‐bound state, high‐energy outward‐occluded intermediate state, with a defined ligand binding cavity. Predictive cysteine cross‐linking in E. coli membranes and PELDOR measurements along the transport cycle indicate that McjD does not undergo major conformational changes as previously proposed for multi‐drug ABC exporters. Combined with transport assays and molecular dynamics simulations, we propose a novel mechanism for toxic peptide ABC exporters that only requires the transient opening of the cavity for release of the peptide. We propose that shielding of the cavity ensures that the transporter is available to export the newly synthesized peptides, preventing toxic‐level build‐up.
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Sep 2017
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