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Zee CT, Glynn C, Gallagher-Jones M, Miao J, Santiago CG, Cascio D, Gonen T, Sawaya MR, Rodriguez JA. Homochiral and racemic MicroED structures of a peptide repeat from the ice-nucleation protein InaZ. IUCRJ 2019; 6:197-205. [PMID: 30867917 PMCID: PMC6400192 DOI: 10.1107/s2052252518017621] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 12/12/2018] [Indexed: 05/29/2023]
Abstract
The ice-nucleation protein InaZ from Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA. Ab initio structures of this repeat segment, resolved to 1.1 Å by microfocus X-ray crystallography and to 0.9 Å by the cryo-EM method MicroED, were determined from both racemic and homochiral crystals. The benefits of racemic protein crystals for structure determination by MicroED were evaluated and it was confirmed that the phase restriction introduced by crystal centrosymmetry increases the number of successful trials during the ab initio phasing of the electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel β-sheets that mate face to back. The racemic GSTSTA protofibril represents a new class of amyloid assembly in which all-left-handed sheets mate with their all-right-handed counterparts. This determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with submicrometre-sized crystals.
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52
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Mondal S, Jacoby G, Sawaya MR, Arnon ZA, Adler-Abramovich L, Rehak P, Vuković L, Shimon LJW, Král P, Beck R, Gazit E. Transition of Metastable Cross-α Crystals into Cross-β Fibrils by β-Turn Flipping. J Am Chem Soc 2018; 141:363-369. [DOI: 10.1021/jacs.8b10289] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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53
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Cao Q, Shin WS, Chan H, Vuong CK, Dubois B, Li B, Murray KA, Sawaya MR, Feigon J, Black DL, Eisenberg DS, Jiang L. Inhibiting amyloid-β cytotoxicity through its interaction with the cell surface receptor LilrB2 by structure-based design. Nat Chem 2018; 10:1213-1221. [PMID: 30297750 PMCID: PMC6250578 DOI: 10.1038/s41557-018-0147-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 08/28/2018] [Indexed: 12/31/2022]
Abstract
Inhibiting the interaction between amyloid-β (Aβ) and a neuronal cell surface receptor, LilrB2, has been suggested as a potential route for treating Alzheimer's disease. Supporting this approach, Alzheimer's-like symptoms are reduced in mouse models following genetic depletion of the LilrB2 homologue. In its pathogenic, oligomeric state, Aβ binds to LilrB2, triggering a pathway to synaptic loss. Here we identify the LilrB2 binding moieties of Aβ (16KLVFFA21) and identify its binding site on LilrB2 from a crystal structure of LilrB2 immunoglobulin domains D1D2 complexed to small molecules that mimic phenylalanine residues. In this structure, we observed two pockets that can accommodate the phenylalanine side chains of KLVFFA. These pockets were confirmed to be 16KLVFFA21 binding sites by mutagenesis. Rosetta docking revealed a plausible geometry for the Aβ-LilrB2 complex and assisted with the structure-guided selection of small molecule inhibitors. These molecules inhibit Aβ-LilrB2 interactions in vitro and on the cell surface and reduce Aβ cytotoxicity, which suggests these inhibitors are potential therapeutic leads against Alzheimer's disease.
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Cao Q, Shin WS, Chan H, Vuong CK, Dubois B, Li B, Murray KA, Sawaya MR, Feigon J, Black DL, Eisenberg DS, Jiang L. Author Correction: Inhibiting amyloid-β cytotoxicity through its interaction with the cell surface receptor LilrB2 by structure-based design. Nat Chem 2018; 10:1267. [PMID: 30420778 DOI: 10.1038/s41557-018-0182-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the version of this Article originally published online, the upper right panel of Fig. 5a was mistakenly a repeat of the lower right panel. This has now been corrected in all versions of the Article.
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Tuukkanen AT, Freire D, Chan S, Arbing MA, Reed RW, Evans TJ, Zenkeviciutė G, Kim J, Kahng S, Sawaya MR, Chaton CT, Wilmanns M, Eisenberg D, Parret AHA, Korotkov KV. Structural Variability of EspG Chaperones from Mycobacterial ESX-1, ESX-3, and ESX-5 Type VII Secretion Systems. J Mol Biol 2018; 431:289-307. [PMID: 30419243 DOI: 10.1016/j.jmb.2018.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 08/28/2018] [Accepted: 11/06/2018] [Indexed: 10/27/2022]
Abstract
Type VII secretion systems (ESX) are responsible for transport of multiple proteins in mycobacteria. How different ESX systems achieve specific secretion of cognate substrates remains elusive. In the ESX systems, the cytoplasmic chaperone EspG forms complexes with heterodimeric PE-PPE substrates that are secreted from the cells or remain associated with the cell surface. Here we report the crystal structure of the EspG1 chaperone from the ESX-1 system determined using a fusion strategy with T4 lysozyme. EspG1 adopts a quasi 2-fold symmetric structure that consists of a central β-sheet and two α-helical bundles. In addition, we describe the structures of EspG3 chaperones from four different crystal forms. Alternate conformations of the putative PE-PPE binding site are revealed by comparison of the available EspG3 structures. Analysis of EspG1, EspG3, and EspG5 chaperones using small-angle X-ray scattering reveals that EspG1 and EspG3 chaperones form dimers in solution, which we observed in several of our crystal forms. Finally, we propose a model of the ESX-3 specific EspG3-PE5-PPE4 complex based on the small-angle X-ray scattering analysis.
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56
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Brumshtein B, Esswein SR, Sawaya MR, Rosenberg G, Ly AT, Landau M, Eisenberg DS. Identification of two principal amyloid-driving segments in variable domains of Ig light chains in systemic light-chain amyloidosis. J Biol Chem 2018; 293:19659-19671. [PMID: 30355736 DOI: 10.1074/jbc.ra118.004142] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 10/18/2018] [Indexed: 11/06/2022] Open
Abstract
Systemic light-chain amyloidosis (AL) is a human disease caused by overexpression of monoclonal immunoglobulin light chains that form pathogenic amyloid fibrils. These amyloid fibrils deposit in tissues and cause organ failure. Proteins form amyloid fibrils when they partly or fully unfold and expose segments capable of stacking into β-sheets that pair and thereby form a tight, dehydrated interface. These structures, termed steric zippers, constitute the spines of amyloid fibrils. Here, using a combination of computational (with ZipperDB and Boston University ALBase), mutational, biochemical, and protein structural analyses, we identified segments within the variable domains of Ig light chains that drive the assembly of amyloid fibrils in AL. We demonstrate that there are at least two such segments and that each one can drive amyloid fibril assembly independently of the other. Our analysis revealed that peptides derived from these segments form steric zippers featuring a typical dry interface with high-surface complementarity and occupy the same spatial location of the Greek-key immunoglobulin fold in both λ and κ variable domains. Of note, some predicted steric-zipper segments did not form amyloid fibrils or assembled into fibrils only when removed from the whole protein. We conclude that steric-zipper propensity must be experimentally validated and that the two segments identified here may represent therapeutic targets. In addition to elucidating the molecular pathogenesis of AL, these findings also provide an experimental approach for identifying segments that drive fibril formation in other amyloid diseases.
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Li B, Ge P, Murray KA, Sheth P, Zhang M, Nair G, Sawaya MR, Shin WS, Boyer DR, Ye S, Eisenberg DS, Zhou ZH, Jiang L. Cryo-EM of full-length α-synuclein reveals fibril polymorphs with a common structural kernel. Nat Commun 2018; 9:3609. [PMID: 30190461 PMCID: PMC6127345 DOI: 10.1038/s41467-018-05971-2] [Citation(s) in RCA: 375] [Impact Index Per Article: 62.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 08/06/2018] [Indexed: 01/19/2023] Open
Abstract
α-Synuclein (aSyn) fibrillar polymorphs have distinct in vitro and in vivo seeding activities, contributing differently to synucleinopathies. Despite numerous prior attempts, how polymorphic aSyn fibrils differ in atomic structure remains elusive. Here, we present fibril polymorphs from the full-length recombinant human aSyn and their seeding capacity and cytotoxicity in vitro. By cryo-electron microscopy helical reconstruction, we determine the structures of the two predominant species, a rod and a twister, both at 3.7 Å resolution. Our atomic models reveal that both polymorphs share a kernel structure of a bent β-arch, but differ in their inter-protofilament interfaces. Thus, different packing of the same kernel structure gives rise to distinct fibril polymorphs. Analyses of disease-related familial mutations suggest their potential contribution to the pathogenesis of synucleinopathies by altering population distribution of the fibril polymorphs. Drug design targeting amyloid fibrils in neurodegenerative diseases should consider the formation and distribution of concurrent fibril polymorphs. The intrinsically disordered protein alpha-synuclein (aSyn) forms polymorphic fibrils. Here the authors provide molecular insights into aSyn fibril polymorphism and present the cryo-EM structures of the two predominant species, a rod and a twister both determined at 3.7 Å resolution.
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Sawaya MR, McPartland L, Heller DM, Eisenberg DS, Hochschild A. Atomic insights into the genesis of cellular filaments by globular proteins. Acta Crystallogr A Found Adv 2018. [DOI: 10.1107/s0108767318095995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Sangwan S, Sawaya MR, Murray KA, Hughes MP, Eisenberg DS. Atomic structures of corkscrew-forming segments of SOD1 reveal varied oligomer conformations. Protein Sci 2018; 27:1231-1242. [PMID: 29453800 PMCID: PMC6032342 DOI: 10.1002/pro.3391] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/14/2018] [Accepted: 02/15/2018] [Indexed: 11/12/2022]
Abstract
The aggregation cascade of disease-related amyloidogenic proteins, terminating in insoluble amyloid fibrils, involves intermediate oligomeric states. The structural and biochemical details of these oligomers have been largely unknown. Here we report crystal structures of variants of the cytotoxic oligomer-forming segment residues 28-38 of the ALS-linked protein, SOD1. The crystal structures reveal three different architectures: corkscrew oligomeric structure, nontwisting curved sheet structure and a steric zipper proto-filament structure. Our work highlights the polymorphism of the segment 28-38 of SOD1 and identifies the molecular features of amyloidogenic entities.
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Saelices L, Sievers SA, Sawaya MR, Eisenberg DS. Crystal structures of amyloidogenic segments of human transthyretin. Protein Sci 2018; 27:1295-1303. [PMID: 29626847 PMCID: PMC6032358 DOI: 10.1002/pro.3420] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 04/03/2018] [Accepted: 04/04/2018] [Indexed: 12/24/2022]
Abstract
Amyloid diseases are characterized by the deposition of proteins in the form of amyloid fibrils, in organs that eventually fail. The development of effective drug candidates follows from the understanding of the molecular processes that lead to protein aggregation. Here, we study amyloidogenic segments of transthyretin (TTR). TTR is a transporter of thyroxine and retinol in the blood and cerebrospinal fluid. When mutated and/or as a result of aging, TTR aggregates into amyloid fibrils that accumulate in organs such as the heart. Recently, we reported two amyloidogenic segments that drive amyloid aggregation. Here, we report the crystal structure of another six amyloidogenic segments of TTR. We found that the segments from the C-terminal region of TTR form in-register steric-zippers with highly-interdigitated, wet interfaces, whereas the β-strand B from the N-terminal region of TTR forms an out-of-register assembly, previously associated with oligomeric formation. Our results contribute fundamental information for understanding the mechanism of aggregation of TTR.
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Robert X, Kassis-Sahyoun J, Ceres N, Martin J, Sawaya MR, Read RJ, Gouet P, Falson P, Chaptal V. Au courant computation of the PDB to audit diffraction anisotropy of soluble and membrane proteins. Data Brief 2018; 19:753-757. [PMID: 30225276 PMCID: PMC6139481 DOI: 10.1016/j.dib.2018.05.072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/15/2018] [Indexed: 02/02/2023] Open
Abstract
This data article makes available the informed computation of the whole Protein Data Bank (PDB) to investigate diffraction anisotropy on a large scale and to perform statistics. This data has been investigated in detail in "X-ray diffraction reveals the intrinsic difference in the physical properties of membrane and soluble proteins" [1]. Diffraction anisotropy is traditionally associated with absence of contacts in-between macromolecules within the crystals in a given direction of space. There are however many case that do not follow this empirical rule. To investigate and sort out this discrepancy, we computed diffraction anisotropy for every entry of the PDB, and put them in context of relevant metrics to compare X-ray diffraction in reciprocal space to the crystal packing in real space. These metrics were either extracted from PDB files when available (resolution, space groups, cell parameters, solvent content), or calculated using standard procedures (anisotropy, crystal contacts, presence of ligands). More specifically, we separated entries to compare soluble vs membrane proteins, and further separated the later in subcategories according to their insertion in the membrane, function, or type of crystallization (Type I vs Type II crystal packing). This informed database is being made available to investigators in the raw and curated formats that can be re-used for further downstream studies. This dataset is useful to test ideas and to ascertain hypothesis based on statistical analysis.
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Hughes MP, Sawaya MR, Boyer DR, Goldschmidt L, Rodriguez JA, Cascio D, Chong L, Gonen T, Eisenberg DS. Atomic structures of low-complexity protein segments reveal kinked β sheets that assemble networks. Science 2018; 359:698-701. [PMID: 29439243 DOI: 10.1126/science.aan6398] [Citation(s) in RCA: 298] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Revised: 11/15/2017] [Accepted: 01/04/2018] [Indexed: 12/16/2022]
Abstract
Subcellular membraneless assemblies are a reinvigorated area of study in biology, with spirited scientific discussions on the forces between the low-complexity protein domains within these assemblies. To illuminate these forces, we determined the atomic structures of five segments from protein low-complexity domains associated with membraneless assemblies. Their common structural feature is the stacking of segments into kinked β sheets that pair into protofilaments. Unlike steric zippers of amyloid fibrils, the kinked sheets interact weakly through polar atoms and aromatic side chains. By computationally threading the human proteome on our kinked structures, we identified hundreds of low-complexity segments potentially capable of forming such interactions. These segments are found in proteins as diverse as RNA binders, nuclear pore proteins, and keratins, which are known to form networks and localize to membraneless assemblies.
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63
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Guenther EL, Ge P, Trinh H, Sawaya MR, Cascio D, Boyer DR, Gonen T, Zhou ZH, Eisenberg DS. Atomic-level evidence for packing and positional amyloid polymorphism by segment from TDP-43 RRM2. Nat Struct Mol Biol 2018. [PMID: 29531287 DOI: 10.1038/s41594-018-0045-5] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Proteins in the fibrous amyloid state are a major hallmark of neurodegenerative disease. Understanding the multiple conformations, or polymorphs, of amyloid proteins at the molecular level is a challenge of amyloid research. Here, we detail the wide range of polymorphs formed by a segment of human TAR DNA-binding protein 43 (TDP-43) as a model for the polymorphic capabilities of pathological amyloid aggregation. Using X-ray diffraction, microelectron diffraction (MicroED) and single-particle cryo-EM, we show that the 247DLIIKGISVHI257 segment from the second RNA-recognition motif (RRM2) forms an array of amyloid polymorphs. These associations include seven distinct interfaces displaying five different symmetry classes of steric zippers. Additionally, we find that this segment can adopt three different backbone conformations that contribute to its polymorphic capabilities. The polymorphic nature of this segment illustrates at the molecular level how amyloid proteins can form diverse fibril structures.
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Do TD, Sangwan S, de Almeida NEC, Ilitchev AI, Giammona M, Sawaya MR, Buratto SK, Eisenberg DS, Bowers MT. Distal amyloid β-protein fragments template amyloid assembly. Protein Sci 2018; 27:1181-1190. [PMID: 29349888 DOI: 10.1002/pro.3375] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 01/16/2018] [Accepted: 01/16/2018] [Indexed: 01/06/2023]
Abstract
Amyloid formation is associated with devastating diseases such as Alzheimer's, Parkinson's and Type-2 diabetes. The large amyloid deposits found in patients suffering from these diseases have remained difficult to probe by structural means. Recent NMR models also predict heterotypic interactions from distinct peptide fragments but limited evidence of heterotypic packed sheets is observed in solution. Here we characterize two segments of the protein amyloid β (Aβ) known to form fibrils in Alzheimer's disease patients. We designed two variants of Aβ(19-24) and Aβ(27-32), IFAEDV (I6V) and NKGAIF (N6F) to lower the aggregation propensity of individual peptides while maintaining the similar interactions between the two segments in their native forms. We found that the variants do not form significant amyloid fibrils individually but a 1:1 mixture forms abundant fibrils. Using ion mobility-mass spectrometry (IM-MS), hetero-oligomers up to decamers were found in the mixture while the individual peptides formed primarily dimers and some tetramers consistent with a strong heterotypic interaction between the two segments. We showed by X-ray crystallography that I6V formed a Class 7 zipper with a weakly packed pair of β-sheets and no segregated dry interface, while N6F formed a more stable Class 1 zipper. In a mixture of equimolar N6F:I6V, I6V forms a more stable zipper than in I6V alone while no N6F or hetero-typic zippers are observed. These data are consistent with a mechanism where N6F catalyzes assembly of I6V into a stable zipper and perhaps into stable, pure I6V fibrils that are observed in AFM measurements.
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Seidler PM, Boyer DR, Rodriguez JA, Sawaya MR, Cascio D, Murray K, Gonen T, Eisenberg DS. Structure-based inhibitors of tau aggregation. Nat Chem 2018; 10:170-176. [PMID: 29359764 PMCID: PMC5784779 DOI: 10.1038/nchem.2889] [Citation(s) in RCA: 207] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 10/04/2017] [Indexed: 12/14/2022]
Abstract
Aggregated tau protein is associated with over 20 neurological disorders, which include Alzheimer's disease. Previous work has shown that tau's sequence segments VQIINK and VQIVYK drive its aggregation, but inhibitors based on the structure of the VQIVYK segment only partially inhibit full-length tau aggregation and are ineffective at inhibiting seeding by full-length fibrils. Here we show that the VQIINK segment is the more powerful driver of tau aggregation. Two structures of this segment determined by the cryo-electron microscopy method micro-electron diffraction explain its dominant influence on tau aggregation. Of practical significance, the structures lead to the design of inhibitors that not only inhibit tau aggregation but also inhibit the ability of exogenous full-length tau fibrils to seed intracellular tau in HEK293 biosensor cells into amyloid. We also raise the possibility that the two VQIINK structures represent amyloid polymorphs of tau that may account for a subset of prion-like strains of tau.
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66
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Hanczyc P, Mikhailovsky A, Boyer DR, Sawaya MR, Heeger A, Eisenberg D. Ultrafast Time-Resolved Studies on Fluorescein for Recognition Strands Architecture in Amyloid Fibrils. J Phys Chem B 2018; 122:8-18. [DOI: 10.1021/acs.jpcb.7b07923] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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67
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Krotee P, Griner SL, Sawaya MR, Cascio D, Rodriguez JA, Shi D, Philipp S, Murray K, Saelices L, Lee J, Seidler P, Glabe CG, Jiang L, Gonen T, Eisenberg DS. Common fibrillar spines of amyloid-β and human islet amyloid polypeptide revealed by microelectron diffraction and structure-based inhibitors. J Biol Chem 2017; 293:2888-2902. [PMID: 29282295 DOI: 10.1074/jbc.m117.806109] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 12/18/2017] [Indexed: 01/21/2023] Open
Abstract
Amyloid-β (Aβ) and human islet amyloid polypeptide (hIAPP) aggregate to form amyloid fibrils that deposit in tissues and are associated with Alzheimer's disease (AD) and type II diabetes (T2D), respectively. Individuals with T2D have an increased risk of developing AD, and conversely, AD patients have an increased risk of developing T2D. Evidence suggests that this link between AD and T2D might originate from a structural similarity between aggregates of Aβ and hIAPP. Using the cryoEM method microelectron diffraction, we determined the atomic structures of 11-residue segments from both Aβ and hIAPP, termed Aβ(24-34) WT and hIAPP(19-29) S20G, with 64% sequence similarity. We observed a high degree of structural similarity between their backbone atoms (0.96-Å root mean square deviation). Moreover, fibrils of these segments induced amyloid formation through self- and cross-seeding. Furthermore, inhibitors designed for one segment showed cross-efficacy for full-length Aβ and hIAPP and reduced cytotoxicity of both proteins, although by apparently blocking different cytotoxic mechanisms. The similarity of the atomic structures of Aβ(24-34) WT and hIAPP(19-29) S20G offers a molecular model for cross-seeding between Aβ and hIAPP.
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Tayeb-Fligelman E, Tabachnikov O, Moshe A, Goldshmidt-Tran O, Sawaya MR, Coquelle N, Colletier JP, Landau M. The cytotoxic Staphylococcus aureus PSMα3 reveals a cross-α amyloid-like fibril. Science 2017; 355:831-833. [PMID: 28232575 DOI: 10.1126/science.aaf4901] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 12/23/2016] [Accepted: 02/02/2017] [Indexed: 12/31/2022]
Abstract
Amyloids are ordered protein aggregates, found in all kingdoms of life, and are involved in aggregation diseases as well as in physiological activities. In microbes, functional amyloids are often key virulence determinants, yet the structural basis for their activity remains elusive. We determined the fibril structure and function of the highly toxic, 22-residue phenol-soluble modulin α3 (PSMα3) peptide secreted by Staphylococcus aureus PSMα3 formed elongated fibrils that shared the morphological and tinctorial characteristics of canonical cross-β eukaryotic amyloids. However, the crystal structure of full-length PSMα3, solved de novo at 1.45 angstrom resolution, revealed a distinctive "cross-α" amyloid-like architecture, in which amphipathic α helices stacked perpendicular to the fibril axis into tight self-associating sheets. The cross-α fibrillation of PSMα3 facilitated cytotoxicity, suggesting that this assembly mode underlies function in S. aureus.
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Popp D, Loh ND, Zorgati H, Ghoshdastider U, Liow LT, Ivanova MI, Larsson M, DePonte DP, Bean R, Beyerlein KR, Gati C, Oberthuer D, Arnlund D, Brändén G, Berntsen P, Cascio D, Chavas LMG, Chen JPJ, Ding K, Fleckenstein H, Gumprecht L, Harimoorthy R, Mossou E, Sawaya MR, Brewster AS, Hattne J, Sauter NK, Seibert M, Seuring C, Stellato F, Tilp T, Eisenberg DS, Messerschmidt M, Williams GJ, Koglin JE, Makowski L, Millane RP, Forsyth T, Boutet S, White TA, Barty A, Chapman H, Chen SL, Liang M, Neutze R, Robinson RC. Flow-aligned, single-shot fiber diffraction using a femtosecond X-ray free-electron laser. Cytoskeleton (Hoboken) 2017; 74:472-481. [PMID: 28574190 DOI: 10.1002/cm.21378] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 05/25/2017] [Accepted: 05/29/2017] [Indexed: 01/26/2023]
Abstract
A major goal for X-ray free-electron laser (XFEL) based science is to elucidate structures of biological molecules without the need for crystals. Filament systems may provide some of the first single macromolecular structures elucidated by XFEL radiation, since they contain one-dimensional translational symmetry and thereby occupy the diffraction intensity region between the extremes of crystals and single molecules. Here, we demonstrate flow alignment of as few as 100 filaments (Escherichia coli pili, F-actin, and amyloid fibrils), which when intersected by femtosecond X-ray pulses result in diffraction patterns similar to those obtained from classical fiber diffraction studies. We also determine that F-actin can be flow-aligned to a disorientation of approximately 5 degrees. Using this XFEL-based technique, we determine that gelsolin amyloids are comprised of stacked β-strands running perpendicular to the filament axis, and that a range of order from fibrillar to crystalline is discernable for individual α-synuclein amyloids.
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Krotee P, Rodriguez JA, Sawaya MR, Cascio D, Reyes FE, Shi D, Hattne J, Nannenga BL, Oskarsson ME, Jiang L, Westermark GT, Gonen T, Eisenberg DS. The Cryo-EM Method Micro-ED Structure Determination of Type II Diabetes-Related Protein Segments. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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72
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Abstract
Dozens of proteins are known to convert to the aggregated amyloid state. These include fibrils associated with systemic and neurodegenerative diseases and cancer, functional amyloid fibrils in microorganisms and animals, and many denatured proteins. Amyloid fibrils can be much more stable than other protein assemblies. In contrast to globular proteins, a single protein sequence can aggregate into several distinctly different amyloid structures, termed polymorphs, and a given polymorph can reproduce itself by seeding. Amyloid polymorphs may be the molecular basis of prion strains. Whereas the Protein Data Bank contains some 100,000 globular protein and 3,000 membrane protein structures, only a few dozen amyloid protein structures have been determined, and most of these are short segments of full amyloid-forming proteins. Regardless, these amyloid structures illuminate the architecture of the amyloid state, including its stability and its capacity for formation of polymorphs.
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Krotee P, Rodriguez JA, Sawaya MR, Cascio D, Reyes FE, Shi D, Hattne J, Nannenga BL, Oskarsson ME, Philipp S, Griner S, Jiang L, Glabe CG, Westermark GT, Gonen T, Eisenberg DS. Atomic structures of fibrillar segments of hIAPP suggest tightly mated β-sheets are important for cytotoxicity. eLife 2017; 6. [PMID: 28045370 PMCID: PMC5207774 DOI: 10.7554/elife.19273] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 12/01/2016] [Indexed: 01/09/2023] Open
Abstract
hIAPP fibrils are associated with Type-II Diabetes, but the link of hIAPP structure to islet cell death remains elusive. Here we observe that hIAPP fibrils are cytotoxic to cultured pancreatic β-cells, leading us to determine the structure and cytotoxicity of protein segments composing the amyloid spine of hIAPP. Using the cryoEM method MicroED, we discover that one segment, 19-29 S20G, forms pairs of β-sheets mated by a dry interface that share structural features with and are similarly cytotoxic to full-length hIAPP fibrils. In contrast, a second segment, 15-25 WT, forms non-toxic labile β-sheets. These segments possess different structures and cytotoxic effects, however, both can seed full-length hIAPP, and cause hIAPP to take on the cytotoxic and structural features of that segment. These results suggest that protein segment structures represent polymorphs of their parent protein and that segment 19-29 S20G may serve as a model for the toxic spine of hIAPP.
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74
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Kattke MD, Chan AH, Duong A, Sexton DL, Sawaya MR, Cascio D, Elliot MA, Clubb RT. Crystal Structure of the Streptomyces coelicolor Sortase E1 Transpeptidase Provides Insight into the Binding Mode of the Novel Class E Sorting Signal. PLoS One 2016; 11:e0167763. [PMID: 27936128 PMCID: PMC5148588 DOI: 10.1371/journal.pone.0167763] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/18/2016] [Indexed: 01/17/2023] Open
Abstract
Many species of Gram-positive bacteria use sortase transpeptidases to covalently affix proteins to their cell wall or to assemble pili. Sortase-displayed proteins perform critical and diverse functions for cell survival, including cell adhesion, nutrient acquisition, and morphological development, among others. Based on their amino acid sequences, there are at least six types of sortases (class A to F enzymes); however, class E enzymes have not been extensively studied. Class E sortases are used by soil and freshwater-dwelling Actinobacteria to display proteins that contain a non-canonical LAXTG sorting signal, which differs from 90% of known sorting signals by substitution of alanine for proline. Here we report the first crystal structure of a class E sortase, the 1.93 Å resolution structure of the SrtE1 enzyme from Streptomyces coelicolor. The active site is bound to a tripeptide, providing insight into the mechanism of substrate binding. SrtE1 possesses β3/β4 and β6/β7 active site loops that contact the LAXTG substrate and are structurally distinct from other classes. We propose that SrtE1 and other class E sortases employ a conserved tyrosine residue within their β3/β4 loop to recognize the amide nitrogen of alanine at position P3 of the sorting signal through a hydrogen bond, as seen here. Incapability of hydrogen-bonding with canonical proline-containing sorting signals likely contributes to class E substrate specificity. Furthermore, we demonstrate that surface anchoring of proteins involved in aerial hyphae formation requires an N-terminal segment in SrtE1 that is presumably positioned within the cytoplasm. Combined, our results reveal unique features within class E enzymes that enable them to recognize distinct sorting signals, and could facilitate the development of substrate-based inhibitors of this important enzyme family.
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Flores BN, Dulchavsky ME, Krans A, Sawaya MR, Paulson HL, Todd PK, Barmada SJ, Ivanova MI. Distinct C9orf72-Associated Dipeptide Repeat Structures Correlate with Neuronal Toxicity. PLoS One 2016; 11:e0165084. [PMID: 27776165 PMCID: PMC5077081 DOI: 10.1371/journal.pone.0165084] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/05/2016] [Indexed: 12/14/2022] Open
Abstract
Hexanucleotide repeat expansions in C9orf72 are the most common inherited cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The expansions elicit toxicity in part through repeat-associated non-AUG (RAN) translation of the intronic (GGGGCC)n sequence into dipeptide repeat-containing proteins (DPRs). Little is known, however, about the structural characteristics and aggregation propensities of the dipeptide units comprising DPRs. To address this question, we synthesized dipeptide units corresponding to the three sense-strand RAN translation products, analyzed their structures by circular dichroism, electron microscopy and dye binding assays, and assessed their relative toxicity when applied to primary cortical neurons. Short, glycine-arginine (GR)3 dipeptides formed spherical aggregates and selectively reduced neuronal survival compared to glycine-alanine (GA)3 and glycine-proline (GP)3 dipeptides. Doubling peptide length had little effect on the structure of GR or GP peptides, but (GA)6 peptides formed β-sheet rich aggregates that bound thioflavin T and Congo red yet lacked the typical fibrillar morphology of amyloids. Aging of (GA)6 dipeptides increased their β-sheet content and enhanced their toxicity when applied to neurons. We also observed that the relative toxicity of each tested dipeptide was proportional to peptide internalization. Our results demonstrate that different C9orf72-related dipeptides exhibit distinct structural properties that correlate with their relative toxicity.
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