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| Open AccessGenetically encoded formaldehyde sensors inspired by a protein intra-helical crosslinking reaction
In order to understand the role of formaldehyde in living systems, real-time monitoring is required. Here the authors report a genetically encoded, reaction-based formaldehyde sensor (FAsor) that enables visualisation of formaldehyde in mammalian cells and tissues.
- Rongfeng Zhu
- , Gong Zhang
- & Peng R. Chen
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Article
| Open AccessA conformation-selective monoclonal antibody against a small molecule-stabilised signalling-deficient form of TNF
TNF can be inhibited by small molecules that stabilize the TNF trimer in an asymmetric conformation. Here, the authors develop a monoclonal antibody that selectively binds this inactive form of TNF, enabling both target engagement assessment and structural characterization of TNF binding to TNF receptor 1.
- Daniel J. Lightwood
- , Rebecca J. Munro
- & Alastair D. G. Lawson
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Article
| Open AccessStructural insights into the disruption of TNF-TNFR1 signalling by small molecules stabilising a distorted TNF
Small molecules stabilising a distorted TNF trimer can inhibit TNF signaling, but the underlying mechanism is unclear. Here, the authors characterize the inhibitor-bound TNF-receptor complex structurally and biochemically, showing that the inhibitors alter TNF-receptor binding stoichiometry and cluster formation.
- David McMillan
- , Carlos Martinez-Fleites
- & James O’Connell
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Article
| Open AccessStructural basis of ribosomal RNA transcription regulation
Ribosomal RNA (rRNA) expression is regulated at the initiation stage of RNA synthesis. Here, the authors report cryo-EM structures of E. coli RNA polymerase and rRNA promoter complex with DksA/ppGpp on the way to open complex formation, identifying key steps in promoter recognition and opening.
- Yeonoh Shin
- , M. Zuhaib Qayyum
- & Katsuhiko S. Murakami
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Article
| Open AccessThe complex structure of GRL0617 and SARS-CoV-2 PLpro reveals a hot spot for antiviral drug discovery
The SARS-CoV-2 papain-like protease (PLpro) is of interest as a drug target. Here, the authors identify GRL0617 as a PPI (protein–protein interaction) inhibitor of SARS-CoV-2 PLpro that inhibits its deISGylating activity and present the mechanism of action of the compound through the GRL0617-bound PLpro crystal structure and NMR studies.
- Ziyang Fu
- , Bin Huang
- & Hao Huang
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Article
| Open AccessStructure of a microtubule-bound axonemal dynein
Axonemal dyneins are tethered to doublet microtubules inside cilia to drive ciliary beating but the mechanisms regulating their localization and function are poorly understood. Here authors report a cryo-EM reconstruction of a three-headed axonemal dynein natively bound to doublet microtubules isolated from cilia which provides a framework to understand the roles of individual subunits.
- Travis Walton
- , Hao Wu
- & Alan Brown
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Article
| Open AccessDistinct mechanisms control genome recognition by p53 at its target genes linked to different cell fates
The tumor suppressor p53 is a master regulator of cellular stress response pathways, including cell cycle arrest and apoptosis. Here, the authors identify molecular mechanisms of p53 binding to high- and low-affinity p53 response elements in the genome, linked to cell cycle arrest and pro-apoptotic genes, respectively.
- Marina Farkas
- , Hideharu Hashimoto
- & Steven B. McMahon
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Article
| Open AccessHigh-fidelity DNA ligation enforces accurate Okazaki fragment maturation during DNA replication
DNA ligase 1 (LIG1) finalizes eukaryotic nuclear DNA synthesis by sealing Okazaki fragments using DNA end-joining reactions. Here the authors, by studying an engineered low-fidelity LIG1, reveal that LIG1 is a highly accurate DNA ligase in vivo.
- Jessica S. Williams
- , Percy P. Tumbale
- & Thomas A. Kunkel
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Article
| Open AccessRab1-AMPylation by Legionella DrrA is allosterically activated by Rab1
The Legionella effector DrrA AMPylates the host protein Rab1 during infection, but the mechanism is still under debate. Here, the authors provide structural insights into the low-affinity DrrA:Rab1 interaction, showing that Rab1 allosterically activates DrrA through a non-conventional binding mechanism.
- Jiqing Du
- , Marie-Kristin von Wrisberg
- & Aymelt Itzen
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Article
| Open AccessCrystal structure of steroid reductase SRD5A reveals conserved steroid reduction mechanism
Steroid 5α-reductase 2 (SRD5A2), a testosterone metabolism enzyme, is implicated in human disease. Structural and biochemical analyses of PbSRD5A, a bacterial homolog, reveal SRD5A2 substrate binding pocket and provide framework for the design of new drugs targeting this enzyme.
- Yufei Han
- , Qian Zhuang
- & Ruobing Ren
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Article
| Open AccessStructure of SRSF1 RRM1 bound to RNA reveals an unexpected bimodal mode of interaction and explains its involvement in SMN1 exon7 splicing
SRSF1 is an oncoprotein that plays important roles in RNA metabolism. We reveal the structure of the human SRSF1 RRM1 bound to RNA, and propose a bimodal mode of interaction of the protein with RNA. A single mutation in RRM1 changed SRSF1 specificity for RNA and made it active on SMN2 exon7 splicing.
- Antoine Cléry
- , Miroslav Krepl
- & Frédéric H.-T. Allain
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Article
| Open AccessStructural analysis of cross α-helical nanotubes provides insight into the designability of filamentous peptide nanomaterials
Peptide-based filamentous assemblies are successfully used for generation of structurally ordered materials, but their de novo design and structural characterization is challenging. Here, the authors provide a strategy for the design of self-assembling peptide nanotubes based on modifications of an arginine clasp interaction motif, and report the cryo-EM structures of seven designed nanotubes.
- Fengbin Wang
- , Ordy Gnewou
- & Vincent P. Conticello
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Article
| Open AccessInositol pyrophosphates promote the interaction of SPX domains with the coiled-coil motif of PHR transcription factors to regulate plant phosphate homeostasis
Plants regulate phosphate homeostasis via the interaction of PHR transcription factors with SPX receptors bound to inositol pyrophosphate signaling molecules. Here the authors show that inositol pyrophosphate-bound SPX interacts with the coiled-coil domain of PHR, which regulates the oligomerization and activity of the transcription factor.
- Martina K. Ried
- , Rebekka Wild
- & Michael Hothorn
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Article
| Open AccessHeme-binding enables allosteric modulation in an ancient TIM-barrel glycosidase
Family 1 glycosidases (GH1) are present in the three domains of life and share classical TIM-barrel fold. Structural and biochemical analyses of a resurrected ancestral GH1 enzyme reveal heme binding, not known in its modern descendants. Heme rigidifies the TIM-barrel and allosterically enhances catalysis.
- Gloria Gamiz-Arco
- , Luis I. Gutierrez-Rus
- & Jose M. Sanchez-Ruiz
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Article
| Open AccessIdentification of fidelity-governing factors in human recombinases DMC1 and RAD51 from cryo-EM structures
RAD51 and DMC1 recombinases catalyse high-fidelity and mismatch tolerant recombination, processes that are indispensable for the maintenance of genomic integrity. Here, the authors via cryo-EM, molecular dynamics simulation and functional analysis elucidate the structural difference between RAD51 and DMC1 with regard to mismatch tolerance.
- Shih-Chi Luo
- , Hsin-Yi Yeh
- & Ming-Daw Tsai
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Article
| Open AccessTwo distinct catalytic pathways for GH43 xylanolytic enzymes unveiled by X-ray and QM/MM simulations
Family 43 glycoside hydrolases (GH43) are involved in the breakdown of hemicellulose. Functional, structural and computational characterization of a GH43 enzyme, including a snapshot of an active Michaelis complex, reveal the hydrolysis mechanism and suggest two possible reaction pathways.
- Mariana A. B. Morais
- , Joan Coines
- & Mario T. Murakami
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Article
| Open AccessAn N-terminal conserved region in human Atg3 couples membrane curvature sensitivity to conjugase activity during autophagy
The E2-like enzyme human Atg3 catalyses the transfer of ubiquitin-like mammalian LC3 to the lipid phosphatidylethanolamine during autophagosome formation. Here, the authors combine NMR measurements with in vitro biochemical and in vivo cellular assays and show that the N-terminal conserved region of human Atg3 communicates information from the curvature-sensing domain to its active site.
- Yansheng Ye
- , Erin R. Tyndall
- & Fang Tian
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Article
| Open AccessStructure of a full-length bacterial polysaccharide co-polymerase
Lipopolysaccharides, important components of the bacterial cell envelope, are synthesized at the inner membrane by the Wzx/Wzy-dependent assembly pathway. A cryo-EM structure of an intact E. coli WzzB, the polysaccharide co-polymerase component of this pathway, reveals details of the transmembrane, cytoplasmic domains and a conserved a proline-rich segment proximal to the C-terminal transmembrane helix.
- Benjamin Wiseman
- , Ram Gopal Nitharwal
- & Martin Högbom
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Article
| Open AccessStructural basis of malaria parasite phenylalanine tRNA-synthetase inhibition by bicyclic azetidines
Bicyclic azetidine inhibitors are promising antimalarials that target the Plasmodium cytosolic phenylalanine tRNAsynthetase (cFRS). Here, Sharma et al. provide the biochemical and structural basis of its mechanism using co-crystal structure of PvcFRS with BRD1389.
- Manmohan Sharma
- , Nipun Malhotra
- & Amit Sharma
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Article
| Open AccessStructural basis of GABARAP-mediated GABAA receptor trafficking and functions on GABAergic synaptic transmission
The GABARAP protein is known to support the stability of GABAA receptors (GABAARs) in synapses, but the underlying molecular mechanisms remained to be elucidated. Here authors use biochemistry, X-ray crystallography and electrophsyiology and show that GABARAP directly binds to a previously unappreciated region in the γ2 subunit of GABAAR.
- Jin Ye
- , Guichang Zou
- & Chao Wang
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Article
| Open AccessAccurate protein structure prediction with hydroxyl radical protein footprinting data
Mass spectrometry-based covalent labeling techniques such as hydroxyl radical protein footprinting (HRPF) provide information about protein tertiary structures. Here, the authors present a dynamics driven HRPF-guided algorithm for protein structure prediction that is incorporated in the Rosetta software suite and only requires the protein sequence and HRPF data as input and they demonstrate its successful application to four benchmark proteins.
- Sarah E. Biehn
- & Steffen Lindert
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Article
| Open AccessMechanism of SARS-CoV-2 polymerase stalling by remdesivir
Remdesivir is a nucleoside analog that inhibits the SARS-CoV-2 RNA dependent RNA polymerase (RdRp) and is used as a drug to treat COVID19 patients. Here, the authors provide insights into the mechanism of remdesivir-induced RdRp stalling by determining the cryo-EM structures of SARS-CoV-2 RdRp with bound RNA molecules that contain remdesivir at defined positions and observe that addition of the fourth nucleotide following remdesivir incorporation into the RNA product is impaired by a barrier to further RNA translocation.
- Goran Kokic
- , Hauke S. Hillen
- & Patrick Cramer
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Article
| Open AccessStructural basis for the multi-activity factor Rad5 in replication stress tolerance
Rad5 is a hub connecting three replication stress tolerance pathways. Here, the authors present the 3.3 Å crystal structure of a N-terminal truncated K.lactis Rad5 construct that reveals the spatial arrangement of the HIRAN, Snf2 and RING domains and structure-guided in vitro and in vivo experiments reveal multiple activities of the yeast Rad5 HIRAN domain among them a role in binding PCNA and supporting its ubiquitination.
- Miaomiao Shen
- , Nalini Dhingra
- & Song Xiang
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Article
| Open AccessEngineering and elucidation of the lipoinitiation process in nonribosomal peptide biosynthesis
Nonribosomal lipopeptides contain an acyl chain important for bioactivity, but its incorporation into the peptidyl backbone, mediated by the starter condensation (Cs) domain of nonribosomal peptide synthases, is not fully understood. Here, the authors show that acyl chains of different lengths can be obtained by engineering Cs domains and identify residues that determine the selectivity for acyl chains.
- Lin Zhong
- , Xiaotong Diao
- & Xiaoying Bian
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Article
| Open AccessStructural insights into TSC complex assembly and GAP activity on Rheb
Tuberous sclerosis complex (TSC) regulates cell growth by controlling the activity of mTORC1. The structure of human TSC complex reveals an arch-shaped, asymmetric architecture and a 2:2:1 stoichiometry of TSC1, TSC2, and TBC1D7 subunits and suggests a mechanism by which TSC2 accelerates GTP hydrolysis against a small GTPase Rheb.
- Huirong Yang
- , Zishuo Yu
- & Yanhui Xu
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Article
| Open AccessCryo-EM structure of Helicobacter pylori urease with an inhibitor in the active site at 2.0 Å resolution
Infection by Helicobacter pylori is associated with peptic ulcers and gastric cancer. H. pylori urease is required for colonization of the stomach and thus an attractive antimicrobial drug target. Cryo-EM analyses of the H. pylori urease with inhibitors bound reveal structural details useful in rational drug design.
- Eva S. Cunha
- , Xiaorui Chen
- & Hartmut Luecke
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Article
| Open AccessDevelopment and structural basis of a two-MAb cocktail for treating SARS-CoV-2 infections
Here, the authors identify and characterize two mouse-derived monoclonal antibodies against SARS-CoV-2 spike protein that target different epitopes in RBD and block the interaction S/ACE2 and show that a formulated humanized version cocktail exhibits prophylaxis and therapeutic antiviral effects in an hACE2-adenovector expressed mouse model.
- Chao Zhang
- , Yifan Wang
- & Zhong Huang
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Article
| Open AccessStabilizing the closed SARS-CoV-2 spike trimer
SARS-CoV-2 S protein prematurely refolds to the post-fusion conformation, compromising immunogenic properties and prefusion trimer yield. Here, Juraszek et al. present a stable SARS-CoV-2 S-closed protein variant with increased expression and correct folding, predominantly in closed prefusion conformation.
- Jarek Juraszek
- , Lucy Rutten
- & Johannes P. M. Langedijk
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Article
| Open AccessStructures of human dual oxidase 1 complex in low-calcium and high-calcium states
Dual oxidases (DUOXs), assembled from the catalytic DUOX and the auxiliary DUOXA subunits, produce hydrogen peroxide by transferring electrons from intracellular NADPH to extracellular oxygen in a calcium-activated manner. Here authors report the cryo-EM structures of human DUOX1-DUOXA1 complex in both high-calcium and low-calcium states.
- Jing-Xiang Wu
- , Rui Liu
- & Lei Chen
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Article
| Open AccessPotent DNA gyrase inhibitors bind asymmetrically to their target using symmetrical bifurcated halogen bonds
The mechanism of DNA gyrase inhibitor stabilization of single-strand DNA cleavage breaks by DNA gyrase has been hypothetical. Here, the authors show experimental evidence of the mechanism using a library of inhibitors with improved binding and employ crystal analysis to show bifurcated halogen bonding.
- Anja Kolarič
- , Thomas Germe
- & Marko Anderluh
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Article
| Open AccessMechanism of filament formation in UPA-promoted CARD8 and NLRP1 inflammasomes
Pathogen triggered N-terminal degradation of NLRP1 and CARD8 by the proteasome releases their C-terminal UPA-CARD fragments (CT) to form the inflammasome, which in turn activates caspase-1. Here, the authors present the cryo-EM structures of the NLRP1-CT and CARD8-CT helical filaments as well as the ASC−caspase-1 octamer structure, which together with in vitro and cell based assays provide further insights into the architecture and specificity of the active NLRP1 and CARD8 inflammasomes.
- L. Robert Hollingsworth
- , Liron David
- & Hao Wu
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Article
| Open AccessInhibiting Mycobacterium tuberculosis CoaBC by targeting an allosteric site
The bifunctional enzyme CoaBC catalyses the second and third step in the Coenzyme A (CoA) biosynthesis pathway and is of interest as a M. tuberculosis drug target. Here, the authors present the full-length crystal structure of Mycobacterium smegmatis CoaBC, which is regulated by CoA and CoA thioesters and forms a dodecamer and by performing a high-throughput screen they identify selective inhibitors of M. tuberculosis CoaB that bind to an allosteric site within CoaB.
- Vitor Mendes
- , Simon R. Green
- & Tom L. Blundell
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Article
| Open AccessStructural basis for distinct inflammasome complex assembly by human NLRP1 and CARD8
NLRP1 and CARD8 are two recently described sensor proteins for the human inflammasome complex. Here, the authors present the cryo-EM CARD filament structures of the NLRP1 and CARD8 activating domains, which reveal how NLRP1 and CARD8 discriminate between ASC and pro-caspase-1. They further propose a two-step model for NLRP1 activation.
- Qin Gong
- , Kim Robinson
- & Bin Wu
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Article
| Open AccessCryo-EM analysis of the HCoV-229E spike glycoprotein reveals dynamic prefusion conformational changes
The spike protein of coronaviruses (S-protein) is an envelope-anchored trimeric type I transmembrane glycoprotein that mediates receptor binding and the fusion of the viral and host cell membranes. Here the authors report the conformational states of HCoV-229E S trimer and observe the conformational changes in S1 subunit from closed state to activated state for receptor binding.
- Xiyong Song
- , Yuejun Shi
- & Guiqing Peng
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Article
| Open AccessStructure and dynamics of the drug-bound bacterial transporter EmrE in lipid bilayers
The small proton-coupled transporter EmrE confers multidrug resistance in bacteria. The structure of drug-bound EmrE in phospholipid bilayers is now determined using solid-state NMR. The structure provides detailed insights into the molecular mechanism of substrate recognition by this transporter.
- Alexander A. Shcherbakov
- , Grant Hisao
- & Mei Hong
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Article
| Open AccessATP synthase hexamer assemblies shape cristae of Toxoplasma mitochondria
Structural and functional analysis of mitochondria from the human parasite Toxoplasma gondii reveals that its ATP synthase assembles into cyclic hexamers, arranged together in a form of pentagonal pyramids required for maintenance of cristae morphology in Apicomplexa.
- Alexander Mühleip
- , Rasmus Kock Flygaard
- & Alexey Amunts
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Article
| Open AccessSeesaw conformations of Npl4 in the human p97 complex and the inhibitory mechanism of a disulfiram derivative
The human AAA+protein p97 plays an important role in cellular protein homeostasis. Here, the authors use cryo-EM to obtain further insights into how p97 interacts with its co-factor Npl4 and they observe three distinct conformational states of Npl4 in complex with human p97, which suggests that a seesaw motion is essential for the unfolding activity of the p97 complex.
- Man Pan
- , Qingyun Zheng
- & Minglei Zhao
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Article
| Open AccessInsights into SusCD-mediated glycan import by a prominent gut symbiont
In Bacteroidetes, SusCD complexes mediate uptake of large nutrients across the outer membrane. SusCD structures in the apo state and in complex with β2,6 fructo-oligosaccharides reveal several substrate molecules in the binding cavity and suggest details of the pedal bin mechanism employed in glycan import.
- Declan A. Gray
- , Joshua B. R. White
- & Bert van den Berg
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Article
| Open AccessFSC-Q: a CryoEM map-to-atomic model quality validation based on the local Fourier shell correlation
Here, the authors present a cryo-EM validation method for the local analysis of the map-to-model fit and introduce FSC-Q as a quality measure. FSC-Q provides a quantitative estimation of how much of the model is supported by the signal content of the map.
- Erney Ramírez-Aportela
- , David Maluenda
- & Carlos Oscar S. Sorzano
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Article
| Open AccessStructural basis for voltage-sensor trapping of the cardiac sodium channel by a deathstalker scorpion toxin
The α-toxin LqhIII from the deathstalker scorpion inhibits fast inactivation of cardiac NaV1.5 channels. Here authors reveal the cryo-EM structure of LqhIII bound to NaV1.5 which shows that LqhIII traps the gating charges of the S4 segment in a unique intermediate-activated state and explains why LqhIII slows inactivation of NaV channels but does not open them.
- Daohua Jiang
- , Lige Tonggu
- & William A. Catterall
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Article
| Open AccessStructural basis for nuclear import selectivity of pioneer transcription factor SOX2
The SOX2 pioneer transcription factor performs critical roles in pluripotency and self-renewal of embryonic stem cells. Here the authors show that SOX2’s two nuclear localization signal sequences form a contiguous binding interface on the nuclear import receptor importin-α3, and provide a structural basis for the preference of SOX2 binding to IMPα3.
- Bikshapathi Jagga
- , Megan Edwards
- & Jade K. Forwood
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Article
| Open AccessHumanizing the yeast origin recognition complex
In most model yeast species the Origin Recognition Complex (ORC) binds defined and species-specific base sequences while in humans what determines the binding appears to be more complex. Here the authors reveal that the yeast’s ORC complex binding specificity is dependent on a 19-amino acid insertion helix in the Orc4 subunit which is lost in human.
- Clare S. K. Lee
- , Ming Fung Cheung
- & Bik-Kwoon Tye
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Article
| Open AccessStructure of the dopamine D2 receptor in complex with the antipsychotic drug spiperone
The dopamine D2 receptor (D2R) is a GPCR and an important drug target for schizophrenia treatment. Here, the authors present the crystal structure of human D2R in complex with the antipsychotic drug spiperone, which is of interest for designing antipsychotics with improved receptor selectivity.
- Dohyun Im
- , Asuka Inoue
- & Tatsuro Shimamura
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Article
| Open AccessBivalent antibody pliers inhibit β-tryptase by an allosteric mechanism dependent on the IgG hinge
β-tryptases are responsible for most of the proteolytic activity during mast cell activation. Here, the authors develop β-tryptase-inhibiting antibodies and provide structural and biochemical evidence that the bivalency of the antibodies is a prerequisite for their inhibitory activity.
- Henry R. Maun
- , Rajesh Vij
- & James T. Koerber
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Article
| Open AccessCryo-electron tomography structure of Arp2/3 complex in cells reveals new insights into the branch junction
The actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Here, authors report a 9.0 Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging.
- Florian Fäßler
- , Georgi Dimchev
- & Florian K. M. Schur
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Article
| Open AccessA method for validating the accuracy of NMR protein structures
The authors present a method for calculating the accuracy of an NMR structure, where flexibility from backbone chemical shifts is compared to structural flexibility predicted using rigidity theory. The authors validate their method and use it to compare the accuracy of NMR and X-ray structures.
- Nicholas J. Fowler
- , Adnan Sljoka
- & Mike P. Williamson
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Article
| Open AccessMycobacterial HelD is a nucleic acids-clearing factor for RNA polymerase
The bacterial helicase-like transcription factor HelD associates with the RNA polymerase (RNAP) and recycles stalled transcription complexes. Here, the authors present the cryo-EM structures of three Mycobacterium smegmatis HelD bound RNAP complexes and further show that HelD can prevent the binding of the RNAP core to non-specific DNA and also actively removes RNAP from stalled elongation complexes.
- Tomáš Kouba
- , Tomáš Koval’
- & Libor Krásný
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Article
| Open AccessThe δ subunit and NTPase HelD institute a two-pronged mechanism for RNA polymerase recycling
The bacterial helicase-like transcription factor HelD interacts with the RNA polymerase (RNAP) and together with the RNAP δ subunit enhances RNAP cycling. Here, the authors present the cryo-EM structures of the monomeric and dimeric Bacillus subtilis RNAP-δ-HelD complexes and suggest a model for HelD/δ-mediated RNAP recycling and putative hibernation.
- Hao-Hong Pei
- , Tarek Hilal
- & Markus C. Wahl
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Article
| Open AccessMolecular basis for RNA polymerase-dependent transcription complex recycling by the helicase-like motor protein HelD
Gram-positive bacteria contain a transcription factor HelD that is able to remove and recycle stalled transcription complexes. Here the authors provide mechanistic insights into this process by determining the cryo-EM structures of the Bacillus subtilis RNA polymerase (RNAP) elongation complex and the RNAP-HelD transcription recycling complex and propose a model of HelD catalysed transcription recycling.
- Timothy P. Newing
- , Aaron J. Oakley
- & Peter J. Lewis