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19 Janelia Publications

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    09/30/20 | Structural insight into the ATP-driven exporter of virulent peptide toxins.
    Zeytuni N, Dickey SW, Hu J, Chou HT, Worrall LJ, Alexander JA, Carlson ML, Nosella M, Duong F, Yu Z, Otto M, Strynadka NC
    Science Advances. 2020 Sep 30;6(40):. doi: 10.1126/sciadv.abb8219

    is a major human pathogen that has acquired alarming broad-spectrum antibiotic resistance. One group of secreted toxins with key roles during infection is the phenol-soluble modulins (PSMs). PSMs are amphipathic, membrane-destructive cytolytic peptides that are exported to the host-cell environment by a designated adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, the PSM transporter (PmtABCD). Here, we demonstrate that the minimal Pmt unit necessary for PSM export is PmtCD and provide its first atomic characterization by single-particle cryo-EM and x-ray crystallography. We have captured the transporter in the ATP-bound state at near atomic resolution, revealing a type II ABC exporter fold, with an additional cytosolic domain. Comparison to a lower-resolution nucleotide-free map displaying an "open" conformation and putative hydrophobic inner chamber of a size able to accommodate the binding of two PSM peptides provides mechanistic insight and sets the foundation for therapeutic design.

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    11/27/19 | Cryo-EM structure of the human FLCN-FNIP2-Rag-Ragulator complex.
    Shen K, Rogala KB, Chou H, Huang RK, Yu Z, Sabatini DM
    Cell. 2019 Nov 27;179(6):1319-29. doi: 10.1016/j.cell.2019.10.036
    08/01/19 | T3S injectisome needle complex structures in four distinct states reveal the basis of membrane coupling and assembly.
    Hu J, Worrall LJ, Vuckovic M, Hong C, Deng W, Atkinson CE, Brett Finlay B, Yu Z, Strynadka NC
    Nature Microbiology. 2019 Aug;4(11):2010-19. doi: 10.1038/s41564-019-0545-z

    The bacterial injectisome is a syringe-shaped macromolecular nanomachine utilized by many pathogenic Gram-negative bacteria, including the causative agents of plague, typhoid fever, whooping cough, sexually transmitted infections and major nosocomial infections. Bacterial proteins destined for self-assembly and host-cell targeting are translocated by the injectisome in a process known as type III secretion (T3S). The core structure is the ~4 MDa needle complex (NC), built on a foundation of three highly oligomerized ring-forming proteins that create a hollow scaffold spanning the bacterial inner membrane (IM) (24-mer ring-forming proteins PrgH and PrgK in the Salmonella entericaserovar Typhimurium Salmonella pathogenicity island 1 (SPI-1) type III secretion system (T3SS)) and outer membrane (OM) (15-mer InvG, a member of the broadly conserved secretin pore family). An internalized helical needle projects from the NC and bacterium, ultimately forming a continuous passage to the host, for delivery of virulence effectors. Here, we have captured snapshots of the entire prototypical SPI-1 NC in four distinct needle assembly states, including near-atomic resolution, and local reconstructions in the absence and presence of the needle. These structures reveal the precise localization and molecular interactions of the internalized SpaPQR ‘export apparatus’ complex, which is intimately encapsulated and stabilized within the IM rings in the manner of a nanodisc, and to which the PrgJ rod directly binds and functions as an initiator and anchor of needle polymerization. We also describe the molecular details of the extensive and continuous coupling interface between the OM secretin and IM rings, which is remarkably facilitated by a localized 16-mer stoichiometry in the periplasmic-most coupling domain of the otherwise 15-mer InvG oligomer.

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    02/07/19 | Cryo-EM structure of the homohexameric T3SS ATPase-central stalk complex reveals rotary ATPase-like asymmetry.
    Majewski DD, Worrall LJ, Hong C, Atkinson CE, Vuckovic M, Watanabe N, Yu Z, Strynadka NC
    Nature Communications. 2019 Feb 07;10(1):626. doi: 10.1038/s41467-019-08477-7

    Many Gram-negative bacteria, including causative agents of dysentery, plague, and typhoid fever, rely on a type III secretion system - a multi-membrane spanning syringe-like apparatus - for their pathogenicity. The cytosolic ATPase complex of this injectisome is proposed to play an important role in energizing secretion events and substrate recognition. We present the 3.3 Å resolution cryo-EM structure of the enteropathogenic Escherichia coli ATPase EscN in complex with its central stalk EscO. The structure shows an asymmetric pore with different functional states captured in its six catalytic sites, details directly supporting a rotary catalytic mechanism analogous to that of the heterohexameric F/V-ATPases despite its homohexameric nature. Situated at the C-terminal opening of the EscN pore is one molecule of EscO, with primary interaction mediated through an electrostatic interface. The EscN-EscO structure provides significant atomic insights into how the ATPase contributes to type III secretion, including torque generation and binding of chaperone/substrate complexes.

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    01/10/19 | Cryo-EM of retinoschisin branched networks suggests an intercellular adhesive scaffold in the retina.
    Heymann JB, Vijayasarathy C, Huang RK, Dearborn AD, Sieving PA, Steven AC
    The Journal of Cell Biology. 2019 Jan 10;218(3):1027-38. doi: 10.1083/jcb.201806148

    Mutations in the retinal protein retinoschisin (RS1) cause progressive loss of vision in young males, a form of macular degeneration called X-linked retinoschisis (XLRS). We previously solved the structure of RS1, a 16-mer composed of paired back-to-back octameric rings. Here, we show by cryo-electron microscopy that RS1 16-mers can assemble into extensive branched networks. We classified the different configurations, finding four types of interaction between the RS1 molecules. The predominant configuration is a linear strand with a wavy appearance. Three less frequent types constitute the branch points of the network. In all cases, the "spikes" around the periphery of the double rings are involved in these interactions. In the linear strand, a loop (usually referred to as spike 1) occurs on both sides of the interface between neighboring molecules. Mutations in this loop suppress secretion, indicating the possibility of intracellular higher-order assembly. These observations suggest that branched networks of RS1 may play a stabilizing role in maintaining the integrity of the retina.

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    12/12/18 | Structure of Plasmodium falciparum Rh5-CyRPA-Ripr invasion complex.
    Wong W, Huang R, Menant S, Hong C, Sandow JJ, Birkinshaw RW, Healer J, Hodder AN, Kanjee U, Tonkin CJ, Heckmann D, Soroka V, Søgaard TM, Jørgensen T, Duraisingh MT, Czabotar PE, de Jongh WA, Tham W, Webb AI, Yu Z, Cowman AF
    Nature. 2018 Dec 12;565(7737):118-21. doi: 10.1038/s41586-018-0779-6

    Plasmodium falciparum causes the severe form of malaria that has high levels of mortality in humans. Blood-stage merozoites of P. falciparum invade erythrocytes, and this requires interactions between multiple ligands from the parasite and receptors in hosts. These interactions include the binding of the Rh5-CyRPA-Ripr complex with the erythrocyte receptor basigin, which is an essential step for entry into human erythrocytes. Here we show that the Rh5-CyRPA-Ripr complex binds the erythrocyte cell line JK-1 significantly better than does Rh5 alone, and that this binding occurs through the insertion of Rh5 and Ripr into host membranes as a complex with high molecular weight. We report a cryo-electron microscopy structure of the Rh5-CyRPA-Ripr complex at subnanometre resolution, which reveals the organization of this essential invasion complex and the mode of interactions between members of the complex, and shows that CyRPA is a critical mediator of complex assembly. Our structure identifies blades 4-6 of the β-propeller of CyRPA as contact sites for Rh5 and Ripr. The limited contacts between Rh5-CyRPA and CyRPA-Ripr are consistent with the dissociation of Rh5 and Ripr from CyRPA for membrane insertion. A comparision of the crystal structure of Rh5-basigin with the cryo-electron microscopy structure of Rh5-CyRPA-Ripr suggests that Rh5 and Ripr are positioned parallel to the erythrocyte membrane before membrane insertion. This provides information on the function of this complex, and thereby provides insights into invasion by P. falciparum.

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    09/21/18 | Cryo-EM analysis of the T3S injectisome reveals the structure of the needle and open secretin.
    Hu J, Worrall LJ, Hong C, Vuckovic M, Atkinson CE, Caveney N, Yu Z, Strynadka NC
    Nature Communications. 2018 Sep 21;9(1):3840. doi: 10.1038/s41467-018-06298-8

    The bacterial type III secretion system, or injectisome, is a syringe shaped nanomachine essential for the virulence of many disease causing Gram-negative bacteria. At the core of the injectisome structure is the needle complex, a continuous channel formed by the highly oligomerized inner and outer membrane hollow rings and a polymerized helical needle filament which spans through and projects into the infected host cell. Here we present the near-atomic resolution structure of a needle complex from the prototypical Salmonella Typhimurium SPI-1 type III secretion system, with local masking protocols allowing for model building and refinement of the major membrane spanning components of the needle complex base in addition to an isolated needle filament. This work provides significant insight into injectisome structure and assembly and importantly captures the molecular basis for substrate induced gating in the giant outer membrane secretin portal family.

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    07/13/18 | Cryo-EM structure of the polycystin 2-l1 ion channel.
    Hulse RE, Li Z, Huang RK, Zhang J, Clapham DE
    eLife. 2018 Jul 13;7:. doi: 10.7554/eLife.36931

    We report the near atomic resolution (3.3 Å) of the human polycystic kidney disease 2-like 1 (polycystin 2-l1) ion channel. Encoded by PKD2L1, polycystin 2-l1 is a calcium and monovalent cation-permeant ion channel in primary cilia and plasma membranes. The related primary cilium-specific polycystin-2 protein, encoded by PKD2, shares a high degree of sequence similarity, yet has distinct permeability characteristics. Here we show that these differences are reflected in the architecture of polycystin 2-l1.

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    07/01/18 | Cryo-EM structure of an essential Plasmodium vivax invasion complex.
    Gruszczyk J, Huang RK, Chan L, Menant S, Hong C, Murphy JM, Mok Y, Griffin MD, Pearson RD, Wong W, Cowman AF, Yu Z, Tham W
    Nature. 2018 Jul;559(7712):135-139. doi: 10.1038/s41586-018-0249-1

    Plasmodium vivax is the most widely distributed malaria parasite that infects humans. P. vivax invades reticulocytes exclusively, and successful entry depends on specific interactions between the P. vivax reticulocyte-binding protein 2b (PvRBP2b) and transferrin receptor 1 (TfR1). TfR1-deficient erythroid cells are refractory to invasion by P. vivax, and anti-PvRBP2b monoclonal antibodies inhibit reticulocyte binding and block P. vivax invasion in field isolates. Here we report a high-resolution cryo-electron microscopy structure of a ternary complex of PvRBP2b bound to human TfR1 and transferrin, at 3.7 Å resolution. Mutational analyses show that PvRBP2b residues involved in complex formation are conserved; this suggests that antigens could be designed that act across P. vivax strains. Functional analyses of TfR1 highlight how P. vivax hijacks TfR1, an essential housekeeping protein, by binding to sites that govern host specificity, without affecting its cellular function of transporting iron. Crystal and solution structures of PvRBP2b in complex with antibody fragments characterize the inhibitory epitopes. Our results establish a structural framework for understanding how P. vivax reticulocyte-binding protein engages its receptor and the molecular mechanism of inhibitory monoclonal antibodies, providing important information for the design of novel vaccine candidates.

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    03/28/18 | Architecture of the human GATOR1 and GATOR1-Rag GTPases complexes.
    Shen K, Huang RK, Brignole EJ, Condon KJ, Valenstein ML, Chantranupong L, Bomaliyamu A, Choe A, Hong C, Yu Z, Sabatini DM
    Nature. 2018 Mar 28;556(7699):64-9. doi: 10.1038/nature26158

    Nutrients, such as amino acids and glucose, signal through the Rag GTPases to activate mTORC1. The GATOR1 protein complex-comprising DEPDC5, NPRL2 and NPRL3-regulates the Rag GTPases as a GTPase-activating protein (GAP) for RAGA; loss of GATOR1 desensitizes mTORC1 signalling to nutrient starvation. GATOR1 components have no sequence homology to other proteins, so the function of GATOR1 at the molecular level is currently unknown. Here we used cryo-electron microscopy to solve structures of GATOR1 and GATOR1-Rag GTPases complexes. GATOR1 adopts an extended architecture with a cavity in the middle; NPRL2 links DEPDC5 and NPRL3, and DEPDC5 contacts the Rag GTPase heterodimer. Biochemical analyses reveal that our GATOR1-Rag GTPases structure is inhibitory, and that at least two binding modes must exist between the Rag GTPases and GATOR1. Direct interaction of DEPDC5 with RAGA inhibits GATOR1-mediated stimulation of GTP hydrolysis by RAGA, whereas weaker interactions between the NPRL2-NPRL3 heterodimer and RAGA execute GAP activity. These data reveal the structure of a component of the nutrient-sensing mTORC1 pathway and a non-canonical interaction between a GAP and its substrate GTPase.

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