1
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Siggel M, Jensen RK, Maurer VJ, Mahamid J, Kosinski J. ColabSeg: An interactive tool for editing, processing, and visualizing membrane segmentations from cryo-ET data. J Struct Biol 2024; 216:108067. [PMID: 38367824 DOI: 10.1016/j.jsb.2024.108067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 01/17/2024] [Accepted: 02/03/2024] [Indexed: 02/19/2024]
Abstract
Cellular cryo-electron tomography (cryo-ET) has emerged as a key method to unravel the spatial and structural complexity of cells in their near-native state at unprecedented molecular resolution. To enable quantitative analysis of the complex shapes and morphologies of lipid membranes, the noisy three-dimensional (3D) volumes must be segmented. Despite recent advances, this task often requires considerable user intervention to curate the resulting segmentations. Here, we present ColabSeg, a Python-based tool for processing, visualizing, editing, and fitting membrane segmentations from cryo-ET data for downstream analysis. ColabSeg makes many well-established algorithms for point-cloud processing easily available to the broad community of structural biologists for applications in cryo-ET through its graphical user interface (GUI). We demonstrate the usefulness of the tool with a range of use cases and biological examples. Finally, for a large Mycoplasma pneumoniae dataset of 50 tomograms, we show how ColabSeg enables high-throughput membrane segmentation, which can be used as valuable training data for fully automated convolutional neural network (CNN)-based segmentation.
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Affiliation(s)
- Marc Siggel
- European Molecular Biology Laboratory (EMBL) Hamburg, Notkestrasse 85, Hamburg 20607, Germany; Centre of Structural Systems Biology (CSSB), Notkestrasse 85, Hamburg 20607, Germany
| | - Rasmus K Jensen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Valentin J Maurer
- European Molecular Biology Laboratory (EMBL) Hamburg, Notkestrasse 85, Hamburg 20607, Germany; Centre of Structural Systems Biology (CSSB), Notkestrasse 85, Hamburg 20607, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg 69117, Germany; Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Jan Kosinski
- European Molecular Biology Laboratory (EMBL) Hamburg, Notkestrasse 85, Hamburg 20607, Germany; Centre of Structural Systems Biology (CSSB), Notkestrasse 85, Hamburg 20607, Germany; Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg 69117, Germany.
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2
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Wan W, Khavnekar S, Wagner J. STOPGAP: an open-source package for template matching, subtomogram alignment and classification. Acta Crystallogr D Struct Biol 2024; 80:336-349. [PMID: 38606666 PMCID: PMC11066880 DOI: 10.1107/s205979832400295x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 04/05/2024] [Indexed: 04/13/2024] Open
Abstract
Cryo-electron tomography (cryo-ET) enables molecular-resolution 3D imaging of complex biological specimens such as viral particles, cellular sections and, in some cases, whole cells. This enables the structural characterization of molecules in their near-native environments, without the need for purification or separation, thereby preserving biological information such as conformational states and spatial relationships between different molecular species. Subtomogram averaging is an image-processing workflow that allows users to leverage cryo-ET data to identify and localize target molecules, determine high-resolution structures of repeating molecular species and classify different conformational states. Here, STOPGAP, an open-source package for subtomogram averaging that is designed to provide users with fine control over each of these steps, is described. In providing detailed descriptions of the image-processing algorithms that STOPGAP uses, this manuscript is also intended to serve as a technical resource to users as well as for further community-driven software development.
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Affiliation(s)
- William Wan
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
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3
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Saphire E, Salie ZL, Ke Z, Halfmann P, DeWald LE, McArdle S, Grinyo A, Davidson E, Schendel S, Hariharan C, Norris M, Yu X, Chennareddy C, Xiong X, Heinrich M, Holbrook M, Doranz B, Crozier I, Hastie K, Kawaoka Y, Branco L, Kuhn J, Briggs J, Worwa G, Davis C, Ahmed R. Anti-Ebola virus mAb 3A6 with unprecedented potency protects highly viremic animals from fatal outcome and physically lifts its glycoprotein target from the virion membrane. RESEARCH SQUARE 2023:rs.3.rs-3722563. [PMID: 38196595 PMCID: PMC10775387 DOI: 10.21203/rs.3.rs-3722563/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Monoclonal antibodies (mAbs) against Ebola virus (EBOV) glycoprotein (GP1,2) are the standard of care for Ebola virus disease (EVD). Anti-GP1,2 mAbs targeting the stalk and membrane proximal external region (MPER) potently neutralize EBOV in vitro. However, their neutralization mechanism is poorly understood because they target a GP1,2 epitope that has evaded structural characterization. Moreover, their in vivo efficacy has only been evaluated in the mouse model of EVD. Using x-ray crystallography and cryo-electron tomography of 3A6 complexed with its stalk- GP1,2 MPER epitope we reveal a novel mechanism in which 3A6 elevates the stalk or stabilizes a conformation of GP1,2 that is lifted from the virion membrane. In domestic guinea pig and rhesus monkey EVD models, 3A6 provides therapeutic benefit at high viremia levels, advanced disease stages, and at the lowest dose yet demonstrated for any anti-EBOV mAb-based monotherapy. These findings can guide design of next-generation, highly potent anti-EBOV mAbs.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | - Xiaoli Xiong
- Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences
| | | | - Michael Holbrook
- National Institute of Allergy and Infectious Diseases (NIAID) Integrated Research Facility, National Institutes of Health (NIH)
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4
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Wan W, Khavnekar S, Wagner J. STOPGAP, an open-source package for template matching, subtomogram alignment, and classification. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572665. [PMID: 38187721 PMCID: PMC10769363 DOI: 10.1101/2023.12.20.572665] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Cryo-electron tomography (cryo-ET) enables molecular-resolution 3D imaging of complex biological specimens such as viral particles, cellular sections, and in some cases, whole cells. This enables the structural characterization of molecules in their near-native environments, without the need for purification or separation, thereby preserving biological information such as conformational states and spatial relationships between different molecular species. Subtomogram averaging is an image processing workflow that allows users to leverage cryo-ET data to identify and localize target molecules, determine high-resolution structures of repeating molecular species, and classifying different conformational states. Here we describe STOPGAP, an open-source package for subtomogram averaging designed to provide users with fine control over each of these steps. In providing detailed descriptions of the image processing algorithms that STOPGAP uses, we intend for this manuscript to also serve as a technical resource to users as well as further community-driven software development.
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Affiliation(s)
- William Wan
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville TN, USA
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5
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Bodakuntla S, Kuhn CC, Biertümpfel C, Mizuno N. Cryo-electron microscopy in the fight against COVID-19-mechanism of virus entry. Front Mol Biosci 2023; 10:1252529. [PMID: 37867557 PMCID: PMC10587472 DOI: 10.3389/fmolb.2023.1252529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 09/20/2023] [Indexed: 10/24/2023] Open
Abstract
Cryogenic electron microscopy (cryo-EM) and electron tomography (cryo-ET) have become a critical tool for studying viral particles. Cryo-EM has enhanced our understanding of viral assembly and replication processes at a molecular resolution. Meanwhile, in situ cryo-ET has been used to investigate how viruses attach to and invade host cells. These advances have significantly contributed to our knowledge of viral biology. Particularly, prompt elucidations of structures of the SARS-CoV-2 spike protein and its variants have directly impacted the development of vaccines and therapeutic measures. This review discusses the progress made by cryo-EM based technologies in comprehending the severe acute respiratory syndrome coronavirus-2 (SARS-Cov-2), the virus responsible for the devastating global COVID-19 pandemic in 2020 with focus on the SARS-CoV-2 spike protein and the mechanisms of the virus entry and replication.
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Affiliation(s)
- Satish Bodakuntla
- Laboratory of Structural Cell Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - Christopher Cyrus Kuhn
- Laboratory of Structural Cell Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - Christian Biertümpfel
- Laboratory of Structural Cell Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - Naoko Mizuno
- Laboratory of Structural Cell Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, United States
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6
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Zhao C, Lu D, Zhao Q, Ren C, Zhang H, Zhai J, Gou J, Zhu S, Zhang Y, Gong X. Computational methods for in situ structural studies with cryogenic electron tomography. Front Cell Infect Microbiol 2023; 13:1135013. [PMID: 37868346 PMCID: PMC10586593 DOI: 10.3389/fcimb.2023.1135013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 08/29/2023] [Indexed: 10/24/2023] Open
Abstract
Cryo-electron tomography (cryo-ET) plays a critical role in imaging microorganisms in situ in terms of further analyzing the working mechanisms of viruses and drug exploitation, among others. A data processing workflow for cryo-ET has been developed to reconstruct three-dimensional density maps and further build atomic models from a tilt series of two-dimensional projections. Low signal-to-noise ratio (SNR) and missing wedge are two major factors that make the reconstruction procedure challenging. Because only few near-atomic resolution structures have been reconstructed in cryo-ET, there is still much room to design new approaches to improve universal reconstruction resolutions. This review summarizes classical mathematical models and deep learning methods among general reconstruction steps. Moreover, we also discuss current limitations and prospects. This review can provide software and methods for each step of the entire procedure from tilt series by cryo-ET to 3D atomic structures. In addition, it can also help more experts in various fields comprehend a recent research trend in cryo-ET. Furthermore, we hope that more researchers can collaborate in developing computational methods and mathematical models for high-resolution three-dimensional structures from cryo-ET datasets.
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Affiliation(s)
- Cuicui Zhao
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Da Lu
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Qian Zhao
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Chongjiao Ren
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Huangtao Zhang
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Jiaqi Zhai
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Jiaxin Gou
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Shilin Zhu
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Yaqi Zhang
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
| | - Xinqi Gong
- Mathematical Intelligence Application LAB, Institute for Mathematical Sciences, Renmin University of China, Beijing, China
- Beijing Academy of Intelligence, Beijing, China
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7
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Huang Y, Zhang Y, Ni T. Towards in situ high-resolution imaging of viruses and macromolecular complexes using cryo-electron tomography. J Struct Biol 2023; 215:108000. [PMID: 37467823 DOI: 10.1016/j.jsb.2023.108000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 07/15/2023] [Accepted: 07/16/2023] [Indexed: 07/21/2023]
Abstract
Cryo-electron tomography and subtomogram averaging are rising and fast-evolving imaging techniques to study biological events, providing structural information at an unprecedented resolution while preserving spatial correlation in their native contexts. The latest technology and methodology development ranging from sample preparation to data collection and data processing, has enabled significant advancement in its applications to various biological systems. This review provides an overview of the current technology development enabling high-resolution structural study in situ, highlighting the use of a priori information of biological samples to assess the quality of subtomogram averaging pipeline. We exemplify the applications of this technique to understanding viruses and principles of macromolecule assembly using different biological systems, ranging from in vitro to in situ samples, which provide structural information at different resolutions and contexts.
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Affiliation(s)
- Yixin Huang
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region
| | - Yu Zhang
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region
| | - Tao Ni
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
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8
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Chaillet ML, van der Schot G, Gubins I, Roet S, Veltkamp RC, Förster F. Extensive Angular Sampling Enables the Sensitive Localization of Macromolecules in Electron Tomograms. Int J Mol Sci 2023; 24:13375. [PMID: 37686180 PMCID: PMC10487639 DOI: 10.3390/ijms241713375] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/23/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
Cryo-electron tomography provides 3D images of macromolecules in their cellular context. To detect macromolecules in tomograms, template matching (TM) is often used, which uses 3D models that are often reliable for substantial parts of the macromolecules. However, the extent of rotational searches in particle detection has not been investigated due to computational limitations. Here, we provide a GPU implementation of TM as part of the PyTOM software package, which drastically speeds up the orientational search and allows for sampling beyond the Crowther criterion within a feasible timeframe. We quantify the improvements in sensitivity and false-discovery rate for the examples of ribosome identification and detection. Sampling at the Crowther criterion, which was effectively impossible with CPU implementations due to the extensive computation times, allows for automated extraction with high sensitivity. Consequently, we also show that an extensive angular sample renders 3D TM sensitive to the local alignment of tilt series and damage induced by focused ion beam milling. With this new release of PyTOM, we focused on integration with other software packages that support more refined subtomogram-averaging workflows. The automated classification of ribosomes by TM with appropriate angular sampling on locally corrected tomograms has a sufficiently low false-discovery rate, allowing for it to be directly used for high-resolution averaging and adequate sensitivity to reveal polysome organization.
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Affiliation(s)
- Marten L. Chaillet
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CG Utrecht, The Netherlands; (M.L.C.); (G.v.d.S.); (S.R.)
| | - Gijs van der Schot
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CG Utrecht, The Netherlands; (M.L.C.); (G.v.d.S.); (S.R.)
| | - Ilja Gubins
- Department of Information and Computing Sciences, Utrecht University, 3584 CC Utrecht, The Netherlands; (I.G.); (R.C.V.)
| | - Sander Roet
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CG Utrecht, The Netherlands; (M.L.C.); (G.v.d.S.); (S.R.)
| | - Remco C. Veltkamp
- Department of Information and Computing Sciences, Utrecht University, 3584 CC Utrecht, The Netherlands; (I.G.); (R.C.V.)
| | - Friedrich Förster
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CG Utrecht, The Netherlands; (M.L.C.); (G.v.d.S.); (S.R.)
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9
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Wozny MR, Di Luca A, Morado DR, Picco A, Khaddaj R, Campomanes P, Ivanović L, Hoffmann PC, Miller EA, Vanni S, Kukulski W. In situ architecture of the ER-mitochondria encounter structure. Nature 2023:10.1038/s41586-023-06050-3. [PMID: 37165187 DOI: 10.1038/s41586-023-06050-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 04/04/2023] [Indexed: 05/12/2023]
Abstract
The endoplasmic reticulum and mitochondria are main hubs of eukaryotic membrane biogenesis that rely on lipid exchange via membrane contact sites1-3, but the underpinning mechanisms remain poorly understood. In yeast, tethering and lipid transfer between the two organelles is mediated by the endoplasmic reticulum-mitochondria encounter structure (ERMES), a four-subunit complex of unresolved stoichiometry and architecture4-6. Here we determined the molecular organization of ERMES within Saccharomyces cerevisiae cells using integrative structural biology by combining quantitative live imaging, cryo-correlative microscopy, subtomogram averaging and molecular modelling. We found that ERMES assembles into approximately 25 discrete bridge-like complexes distributed irregularly across a contact site. Each bridge consists of three synaptotagmin-like mitochondrial lipid binding protein domains oriented in a zig-zag arrangement. Our molecular model of ERMES reveals a pathway for lipids. These findings resolve the in situ supramolecular architecture of a major inter-organelle lipid transfer machinery and provide a basis for the mechanistic understanding of lipid fluxes in eukaryotic cells.
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Affiliation(s)
- Michael R Wozny
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Andrea Di Luca
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Dustin R Morado
- MRC Laboratory of Molecular Biology, Cambridge, UK
- SciLifeLab, Solna, Sweden
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Andrea Picco
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Rasha Khaddaj
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Pablo Campomanes
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Lazar Ivanović
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Patrick C Hoffmann
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | | | - Stefano Vanni
- Department of Biology, University of Fribourg, Fribourg, Switzerland.
| | - Wanda Kukulski
- MRC Laboratory of Molecular Biology, Cambridge, UK.
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
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10
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von Kügelgen A, van Dorst S, Yamashita K, Sexton DL, Tocheva EI, Murshudov G, Alva V, Bharat TAM. Interdigitated immunoglobulin arrays form the hyperstable surface layer of the extremophilic bacterium Deinococcus radiodurans. Proc Natl Acad Sci U S A 2023; 120:e2215808120. [PMID: 37043530 PMCID: PMC10120038 DOI: 10.1073/pnas.2215808120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 03/14/2023] [Indexed: 04/13/2023] Open
Abstract
Deinococcus radiodurans is an atypical diderm bacterium with a remarkable ability to tolerate various environmental stresses, due in part to its complex cell envelope encapsulated within a hyperstable surface layer (S-layer). Despite decades of research on this cell envelope, atomic structural details of the S-layer have remained obscure. In this study, we report the electron cryomicroscopy structure of the D. radiodurans S-layer, showing how it is formed by the Hexagonally Packed Intermediate-layer (HPI) protein arranged in a planar hexagonal lattice. The HPI protein forms an array of immunoglobulin-like folds within the S-layer, with each monomer extending into the adjacent hexamer, resulting in a highly interconnected, stable, sheet-like arrangement. Using electron cryotomography and subtomogram averaging from focused ion beam-milled D. radiodurans cells, we have obtained a structure of the cellular S-layer, showing how this HPI S-layer coats native membranes on the surface of cells. Our S-layer structure from the diderm bacterium D. radiodurans shows similarities to immunoglobulin-like domain-containing S-layers from monoderm bacteria and archaea, highlighting common features in cell surface organization across different domains of life, with connotations on the evolution of immunoglobulin-based molecular recognition systems in eukaryotes.
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Affiliation(s)
- Andriko von Kügelgen
- Structural Studies Division, MRC Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, OxfordOX1 3RE, United Kingdom
| | - Sofie van Dorst
- Sir William Dunn School of Pathology, University of Oxford, OxfordOX1 3RE, United Kingdom
| | - Keitaro Yamashita
- Structural Studies Division, MRC Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - Danielle L. Sexton
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BCV6T 1Z3, Canada
| | - Elitza I. Tocheva
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BCV6T 1Z3, Canada
| | - Garib Murshudov
- Structural Studies Division, MRC Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - Vikram Alva
- Department of Protein Evolution, Max Planck Institute for Biology Tübingen, Tübingen72076, Germany
| | - Tanmay A. M. Bharat
- Structural Studies Division, MRC Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, OxfordOX1 3RE, United Kingdom
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11
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Wang C, Wojtynek M, Medalia O. Structural investigation of eukaryotic cells: From the periphery to the interior by cryo-electron tomography. Adv Biol Regul 2023; 87:100923. [PMID: 36280452 DOI: 10.1016/j.jbior.2022.100923] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/05/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
Abstract
Cryo-electron tomography (cryo-ET) combines a close-to-life preservation of the cell with high-resolution three-dimensional (3D) imaging. This allows to study the molecular architecture of the cellular landscape and provides unprecedented views on biological processes and structures. In this review we mainly focus on the application of cryo-ET to visualize and structurally characterize eukaryotic cells - from the periphery to the cellular interior. We discuss strategies that can be employed to investigate the structure of challenging targets in their cellular environment as well as the application of complimentary approaches in conjunction with cryo-ET.
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Affiliation(s)
- Chunyang Wang
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Matthias Wojtynek
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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12
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Dahmane S, Kerviel A, Morado DR, Shankar K, Ahlman B, Lazarou M, Altan-Bonnet N, Carlson LA. Membrane-assisted assembly and selective secretory autophagy of enteroviruses. Nat Commun 2022; 13:5986. [PMID: 36216808 PMCID: PMC9550805 DOI: 10.1038/s41467-022-33483-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 09/20/2022] [Indexed: 11/09/2022] Open
Abstract
Enteroviruses are non-enveloped positive-sense RNA viruses that cause diverse diseases in humans. Their rapid multiplication depends on remodeling of cytoplasmic membranes for viral genome replication. It is unknown how virions assemble around these newly synthesized genomes and how they are then loaded into autophagic membranes for release through secretory autophagy. Here, we use cryo-electron tomography of infected cells to show that poliovirus assembles directly on replication membranes. Pharmacological untethering of capsids from membranes abrogates RNA encapsidation. Our data directly visualize a membrane-bound half-capsid as a prominent virion assembly intermediate. Assembly progression past this intermediate depends on the class III phosphatidylinositol 3-kinase VPS34, a key host-cell autophagy factor. On the other hand, the canonical autophagy initiator ULK1 is shown to restrict virion production since its inhibition leads to increased accumulation of virions in vast intracellular arrays, followed by an increased vesicular release at later time points. Finally, we identify multiple layers of selectivity in virus-induced autophagy, with a strong selection for RNA-loaded virions over empty capsids and the segregation of virions from other types of autophagosome contents. These findings provide an integrated structural framework for multiple stages of the poliovirus life cycle.
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Affiliation(s)
- Selma Dahmane
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Adeline Kerviel
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Dustin R Morado
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Kasturika Shankar
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Björn Ahlman
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Michael Lazarou
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Nihal Altan-Bonnet
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Lars-Anders Carlson
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden. .,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden. .,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.
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13
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Walsh RM, Mayer ML, Sun CH, Rawson S, Nair R, Sterling SM, Li Z. Practices for running a research-oriented shared cryo-EM facility. Front Mol Biosci 2022; 9:960940. [PMID: 36188224 PMCID: PMC9521047 DOI: 10.3389/fmolb.2022.960940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/18/2022] [Indexed: 11/13/2022] Open
Abstract
The Harvard Cryo-Electron Microscopy Center for Structural Biology, which was formed as a consortium between Harvard Medical School, Boston Children’s Hospital, Dana-Farber Cancer Institute, and Massachusetts General Hospital, serves both academic and commercial users in the greater Harvard community. The facility strives to optimize research productivity while training users to become expert electron microscopists. These two tasks may be at odds and require careful balance to keep research projects moving forward while still allowing trainees to develop independence and expertise. This article presents the model developed at Harvard Medical School for running a research-oriented cryo-EM facility. Being a research-oriented facility begins with training in cryo-sample preparation on a trainee’s own sample, ideally producing grids that can be screened and optimized on the Talos Arctica via multiple established pipelines. The first option, staff assisted screening, requires no user experience and a staff member provides instant feedback about the suitability of the sample for cryo-EM investigation and discusses potential strategies for sample optimization. Another option, rapid access, allows users short sessions to screen samples and introductory training for basic microscope operation. Once a sample reaches the stage where data collection is warranted, new users are trained on setting up data collection for themselves on either the Talos Arctica or Titan Krios microscope until independence is established. By providing incremental training and screening pipelines, the bottleneck of sample preparation can be overcome in parallel with developing skills as an electron microscopist. This approach allows for the development of expertise without hindering breakthroughs in key research areas.
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Affiliation(s)
- Richard M. Walsh
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Megan L. Mayer
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Christopher H. Sun
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Shaun Rawson
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Remya Nair
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Sarah M. Sterling
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
| | - Zongli Li
- Harvard Cryo-EM Center for Structural Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, United States
- Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, United States
- *Correspondence: Zongli Li,
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14
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Kralt A, Wojtynek M, Fischer JS, Agote-Aran A, Mancini R, Dultz E, Noor E, Uliana F, Tatarek-Nossol M, Antonin W, Onischenko E, Medalia O, Weis K. An amphipathic helix in Brl1 is required for nuclear pore complex biogenesis in S. cerevisiae. eLife 2022; 11:78385. [PMID: 36000978 PMCID: PMC9402233 DOI: 10.7554/elife.78385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 08/03/2022] [Indexed: 12/28/2022] Open
Abstract
The nuclear pore complex (NPC) is the central portal for macromolecular exchange between the nucleus and cytoplasm. In all eukaryotes, NPCs assemble into an intact nuclear envelope (NE) during interphase, but the process of NPC biogenesis remains poorly characterized. Furthermore, little is known about how NPC assembly leads to the fusion of the outer and inner NE, and no factors have been identified that could trigger this event. Here, we characterize the transmembrane protein Brl1 as an NPC assembly factor required for NE fusion in budding yeast. Brl1 preferentially associates with NPC assembly intermediates and its depletion halts NPC biogenesis, leading to NE herniations that contain inner and outer ring nucleoporins but lack the cytoplasmic export platform. Furthermore, we identify an essential amphipathic helix in the luminal domain of Brl1 that mediates interactions with lipid bilayers. Mutations in this amphipathic helix lead to NPC assembly defects, and cryo-electron tomography analyses reveal multilayered herniations of the inner nuclear membrane with NPC-like structures at the neck, indicating a failure in NE fusion. Taken together, our results identify a role for Brl1 in NPC assembly and suggest a function of its amphipathic helix in mediating the fusion of the inner and outer nuclear membranes.
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Affiliation(s)
- Annemarie Kralt
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Matthias Wojtynek
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland.,Department of Biochemistry, University of Zurich, Zürich, Switzerland
| | - Jonas S Fischer
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Arantxa Agote-Aran
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Roberta Mancini
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Elisa Dultz
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Elad Noor
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Federico Uliana
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Marianna Tatarek-Nossol
- Institute of Biochemistry and Molecular Cell Biology, Medical School, RWTH Aachen University, Aachen, Germany
| | - Wolfram Antonin
- Institute of Biochemistry and Molecular Cell Biology, Medical School, RWTH Aachen University, Aachen, Germany
| | - Evgeny Onischenko
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Zürich, Switzerland
| | - Karsten Weis
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
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15
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von Kügelgen A, van Dorst S, Alva V, Bharat TAM. A multidomain connector links the outer membrane and cell wall in phylogenetically deep-branching bacteria. Proc Natl Acad Sci U S A 2022; 119:e2203156119. [PMID: 35943982 PMCID: PMC9388160 DOI: 10.1073/pnas.2203156119] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 06/24/2022] [Indexed: 01/30/2023] Open
Abstract
Deinococcus radiodurans is a phylogenetically deep-branching extremophilic bacterium that is remarkably tolerant to numerous environmental stresses, including large doses of ultraviolet (UV) radiation and extreme temperatures. It can even survive in outer space for several years. This endurance of D. radiodurans has been partly ascribed to its atypical cell envelope comprising an inner membrane, a large periplasmic space with a thick peptidoglycan (PG) layer, and an outer membrane (OM) covered by a surface layer (S-layer). Despite intense research, molecular principles governing envelope organization and OM stabilization are unclear in D. radiodurans and related bacteria. Here, we report a electron cryomicroscopy (cryo-EM) structure of the abundant D. radiodurans OM protein SlpA, showing how its C-terminal segment forms homotrimers of 30-stranded β-barrels in the OM, whereas its N-terminal segment forms long, homotrimeric coiled coils linking the OM to the PG layer via S-layer homology (SLH) domains. Furthermore, using protein structure prediction and sequence-based bioinformatic analysis, we show that SlpA-like putative OM-PG connector proteins are widespread in phylogenetically deep-branching Gram-negative bacteria. Finally, combining our atomic structures with fluorescence and electron microscopy of cell envelopes of wild-type and mutant bacterial strains, we report a model for the cell surface of D. radiodurans. Our results will have important implications for understanding the cell surface organization and hyperstability of D. radiodurans and related bacteria and the evolutionary transition between Gram-negative and Gram-positive bacteria.
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Affiliation(s)
- Andriko von Kügelgen
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Sofie van Dorst
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Vikram Alva
- Department of Protein Evolution, Max Planck Institute for Biology Tübingen, Tübingen 72076, Germany
| | - Tanmay A. M. Bharat
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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16
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Schneider J, Jasnin M. Capturing actin assemblies in cells using in situ cryo-electron tomography. Eur J Cell Biol 2022; 101:151224. [PMID: 35500467 DOI: 10.1016/j.ejcb.2022.151224] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 11/21/2022] Open
Abstract
Actin contributes to an exceptionally wide range of cellular processes through the assembly and disassembly of highly dynamic and ordered structures. Visualizing these structures in cells can help us understand how the molecular players of the actin machinery work together to produce force-generating systems. In recent years, cryo-electron tomography (cryo-ET) has become the method of choice for structural analysis of the cell interior at the molecular scale. Here we review advances in cryo-ET workflows that have enabled this transformation, especially the automation of sample preparation procedures, data collection, and processing. We discuss new structural analyses of dynamic actin assemblies in cryo-preserved cells, which have provided mechanistic insights into actin assembly and function at the nanoscale. Finally, we highlight the latest visual proteomics studies of actin filaments and their interactors reaching sub-nanometer resolutions in cells.
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Affiliation(s)
- Jonathan Schneider
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Marion Jasnin
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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17
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Selnihhin D, Mortensen KI, Larsen JB, Simonsen JB, Pedersen FS. DNA Origami Calibrators for Counting Fluorophores on Single Particles by Flow Cytometry. SMALL METHODS 2022; 6:e2101364. [PMID: 34994103 DOI: 10.1002/smtd.202101364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/09/2021] [Indexed: 06/14/2023]
Abstract
Flow cytometry (FCM) is a high-throughput fluorescence-based technique for multiparameter analysis of individual particles, including cells and nanoparticles. Currently, however, FCM does in many cases not permit proper counting of fluorophore-tagged markers on individual particles, due to a lack of tools for translating FCM output intensities into accurate numbers of fluorophores. This lack hinders derivation of detailed biologic information and comparison of data between experiments with FCM. To address this technological void, the authors here use DNA nanotechnology to design and construct barrel-shaped DNA-origami nanobeads for fluorescence/antigen quantification in FCM. Each bead contains a specific number of calibrator fluorophores and a fluorescent trigger domain with an alternative fluorophore for proper detection in FCM. Using electron microscopy, single-particle fluorescence microscopy, and FCM, the design of each particle is verified. To validate that the DNA bead-based FCM calibration enabled the authors to determine the number of antigens on a biological particle, the uniform and well-characterized murine leukemia virus (MLV) is studied. 48 ± 11 envelope surface protein (Env) trimers per MLV is obtained, which is consistent with reported numbers that relied on low-throughput imaging. Thus, the authors' DNA-beads should accelerate quantitative studies of the biology of individual particles with FCM.
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Affiliation(s)
- Denis Selnihhin
- Department of Molecular Biology and Genetics, Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, 8000, Denmark
- Department of Health Technology, Technical University of Denmark, Lyngby, 2800, Denmark
| | - Kim I Mortensen
- Department of Health Technology, Technical University of Denmark, Lyngby, 2800, Denmark
| | - Jannik B Larsen
- Department of Health Technology, Technical University of Denmark, Lyngby, 2800, Denmark
| | - Jens B Simonsen
- Department of Health Technology, Technical University of Denmark, Lyngby, 2800, Denmark
| | - Finn Skou Pedersen
- Department of Molecular Biology and Genetics, Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, 8000, Denmark
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18
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Obr M, JH Hagen W, Dick RA, Yu L, Kotecha A, KM Schur F. Exploring high-resolution cryo-ET and subtomogram averaging capabilities of contemporary DEDs. J Struct Biol 2022; 214:107852. [DOI: 10.1016/j.jsb.2022.107852] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/20/2022] [Accepted: 03/23/2022] [Indexed: 01/26/2023]
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19
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Subtomogram analysis: The sum of a tomogram's particles reveals molecular structure in situ. J Struct Biol X 2022; 6:100063. [PMID: 36684812 PMCID: PMC9846452 DOI: 10.1016/j.yjsbx.2022.100063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 01/25/2022] [Indexed: 01/25/2023] Open
Abstract
Cryo-electron tomography is uniquely suited to provide insights into the molecular architecture of cells and tissue in the native state. While frozen hydrated specimens tolerate sufficient electron doses to distinguish different types of particles in a tomogram, the accumulating beam damage does not allow resolving their detailed molecular structure individually. Statistical methods for subtomogram averaging and classification that coherently enhance the signal of particles corresponding to copies of the same type of macromolecular allow obtaining much higher resolution insights into macromolecules. Here, I review the developments in subtomogram analysis at Wolfgang Baumeister's laboratory that make the dream of structural biology in the native cell become reality.
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20
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Zivanov J, Otón J, Ke Z, von Kügelgen A, Pyle E, Qu K, Morado D, Castaño-Díez D, Zanetti G, Bharat TAM, Briggs JAG, Scheres SHW. A Bayesian approach to single-particle electron cryo-tomography in RELION-4.0. eLife 2022; 11:83724. [PMID: 36468689 PMCID: PMC9815803 DOI: 10.7554/elife.83724] [Citation(s) in RCA: 79] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 12/04/2022] [Indexed: 12/12/2022] Open
Abstract
We present a new approach for macromolecular structure determination from multiple particles in electron cryo-tomography (cryo-ET) data sets. Whereas existing subtomogram averaging approaches are based on 3D data models, we propose to optimise a regularised likelihood target that approximates a function of the 2D experimental images. In addition, analogous to Bayesian polishing and contrast transfer function (CTF) refinement in single-particle analysis, we describe the approaches that exploit the increased signal-to-noise ratio in the averaged structure to optimise tilt-series alignments, beam-induced motions of the particles throughout the tilt-series acquisition, defoci of the individual particles, as well as higher-order optical aberrations of the microscope. Implementation of our approaches in the open-source software package RELION aims to facilitate their general use, particularly for those researchers who are already familiar with its single-particle analysis tools. We illustrate for three applications that our approaches allow structure determination from cryo-ET data to resolutions sufficient for de novo atomic modelling.
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Affiliation(s)
- Jasenko Zivanov
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Laboratory of Biomedical Imaging (LIB)LausanneSwitzerland,BioEM lab, Biozentrum, University of BaselBaselSwitzerland
| | - Joaquín Otón
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,ALBA SynchrotronBarcelonaSpain
| | - Zunlong Ke
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Max Planck Institute of BiochemistryMartinsriedGermany
| | - Andriko von Kügelgen
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Sir William Dunn School of Pathology, University of OxfordOxfordUnited Kingdom
| | - Euan Pyle
- Institute of Structural and Molecular Biology, Birkbeck CollegeLondonUnited Kingdom
| | - Kun Qu
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Dustin Morado
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Max Planck Institute of BiochemistryMartinsriedGermany
| | - Daniel Castaño-Díez
- BioEM lab, Biozentrum, University of BaselBaselSwitzerland,Instituto BiofisikaLeioaSpain
| | - Giulia Zanetti
- Institute of Structural and Molecular Biology, Birkbeck CollegeLondonUnited Kingdom
| | - Tanmay AM Bharat
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Sir William Dunn School of Pathology, University of OxfordOxfordUnited Kingdom
| | - John AG Briggs
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom,Max Planck Institute of BiochemistryMartinsriedGermany
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21
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von Kügelgen A, Alva V, Bharat TAM. Complete atomic structure of a native archaeal cell surface. Cell Rep 2021; 37:110052. [PMID: 34818541 PMCID: PMC8640222 DOI: 10.1016/j.celrep.2021.110052] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/28/2021] [Accepted: 11/01/2021] [Indexed: 12/20/2022] Open
Abstract
Many prokaryotic cells are covered by an ordered, proteinaceous, sheet-like structure called a surface layer (S-layer). S-layer proteins (SLPs) are usually the highest copy number macromolecules in prokaryotes, playing critical roles in cellular physiology such as blocking predators, scaffolding membranes, and facilitating environmental interactions. Using electron cryomicroscopy of two-dimensional sheets, we report the atomic structure of the S-layer from the archaeal model organism Haloferax volcanii. This S-layer consists of a hexagonal array of tightly interacting immunoglobulin-like domains, which are also found in SLPs across several classes of archaea. Cellular tomography reveal that the S-layer is nearly continuous on the cell surface, completed by pentameric defects in the hexagonal lattice. We further report the atomic structure of the SLP pentamer, which shows markedly different relative arrangements of SLP domains needed to complete the S-layer. Our structural data provide a framework for understanding cell surfaces of archaea at the atomic level.
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Affiliation(s)
| | - Vikram Alva
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK; Structural Studies Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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22
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Scaramuzza S, Castaño-Díez D. Step-by-step guide to efficient subtomogram averaging of virus-like particles with Dynamo. PLoS Biol 2021; 19:e3001318. [PMID: 34437529 PMCID: PMC8389376 DOI: 10.1371/journal.pbio.3001318] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 06/09/2021] [Indexed: 11/19/2022] Open
Abstract
Subtomogram averaging (STA) is a powerful image processing technique in electron tomography used to determine the 3D structure of macromolecular complexes in their native environments. It is a fast growing technique with increasing importance in structural biology. The computational aspect of STA is very complex and depends on a large number of variables. We noticed a lack of detailed guides for STA processing. Also, current publications in this field often lack a documentation that is practical enough to reproduce the results with reasonable effort, which is necessary for the scientific community to grow. We therefore provide a complete, detailed, and fully reproducible processing protocol that covers all aspects of particle picking and particle alignment in STA. The command line-based workflow is fully based on the popular Dynamo software for STA. Within this workflow, we also demonstrate how large parts of the processing pipeline can be streamlined and automatized for increased throughput. This protocol is aimed at users on all levels. It can be used for training purposes, or it can serve as basis to design user-specific projects by taking advantage of the flexibility of Dynamo by modifying and expanding the given pipeline. The protocol is successfully validated using the Electron Microscopy Public Image Archive (EMPIAR) database entry 10164 from immature HIV-1 virus-like particles (VLPs) that describe a geometry often seen in electron tomography.
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23
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Qu K, Ke Z, Zila V, Anders-Össwein M, Glass B, Mücksch F, Müller R, Schultz C, Müller B, Kräusslich HG, Briggs JAG. Maturation of the matrix and viral membrane of HIV-1. Science 2021; 373:700-704. [PMID: 34353956 DOI: 10.1126/science.abe6821] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 06/24/2021] [Indexed: 12/22/2022]
Abstract
Gag, the primary structural protein of HIV-1, is recruited to the plasma membrane for virus assembly by its matrix (MA) domain. Gag is subsequently cleaved into its component domains, causing structural maturation to repurpose the virion for cell entry. We determined the structure and arrangement of MA within immature and mature HIV-1 through cryo-electron tomography. We found that MA rearranges between two different hexameric lattices upon maturation. In mature HIV-1, a lipid extends out of the membrane to bind with a pocket in MA. Our data suggest that proteolytic maturation of HIV-1 not only assembles the viral capsid surrounding the genome but also repurposes the membrane-bound MA lattice for an entry or postentry function and results in the partial removal of up to 2500 lipids from the viral membrane.
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Affiliation(s)
- Kun Qu
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany.,Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany
| | - Zunlong Ke
- Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany.,Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK
| | - Vojtech Zila
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.,Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany
| | - Maria Anders-Össwein
- Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany
| | - Bärbel Glass
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany
| | - Frauke Mücksch
- Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany
| | - Rainer Müller
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Carsten Schultz
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR 97239, USA
| | - Barbara Müller
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany
| | - Hans-Georg Kräusslich
- Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.,Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany.,Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany.,German Center for Infection Research, Heidelberg, Germany
| | - John A G Briggs
- Department of Infectious Diseases, Virology, Universitätsklinikum Heidelberg, 69120 Heidelberg, Germany. .,Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany.,Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Molecular Medicine Partnership Unit, European Molecular Biology Laboratory and Universitätsklinikum Heidelberg, 69117 Heidelberg, Germany
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24
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Han R, Li L, Yang P, Zhang F, Gao X. A novel constrained reconstruction model towards high-resolution subtomogram averaging. Bioinformatics 2021; 37:1616-1626. [PMID: 31617571 DOI: 10.1093/bioinformatics/btz787] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 08/12/2019] [Accepted: 10/14/2019] [Indexed: 11/15/2022] Open
Abstract
MOTIVATION Electron tomography (ET) offers a unique capacity to image biological structures in situ. However, the resolution of ET reconstructed tomograms is not comparable to that of the single-particle cryo-EM. If many copies of the object of interest are present in the tomograms, their structures can be reconstructed in the tomogram, picked, aligned and averaged to increase the signal-to-noise ratio and improve the resolution, which is known as the subtomogram averaging. To date, the resolution improvement of the subtomogram averaging is still limited because each reconstructed subtomogram is of low reconstruction quality due to the missing wedge issue. RESULTS In this article, we propose a novel computational model, the constrained reconstruction model (CRM), to better recover the information from the multiple subtomograms and compensate for the missing wedge issue in each of them. CRM is supposed to produce a refined reconstruction in the final turn of subtomogram averaging after alignment, instead of directly taking the average. We first formulate the averaging method and our CRM as linear systems, and prove that the solution space of CRM is no larger, and in practice much smaller, than that of the averaging method. We then propose a sparse Kaczmarz algorithm to solve the formulated CRM, and further extend the solution to the simultaneous algebraic reconstruction technique (SART). Experimental results demonstrate that CRM can significantly alleviate the missing wedge issue and improve the final reconstruction quality. In addition, our model is robust to the number of images in each tilt series, the tilt range and the noise level. AVAILABILITY AND IMPLEMENTATION The codes of CRM-SIRT and CRM-SART are available at https://github.com/icthrm/CRM. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Renmin Han
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Lun Li
- High Performance Computer Research Center, Institute of Computing Technology, Chinese Academy of Sciences, 100190 Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Peng Yang
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Fa Zhang
- High Performance Computer Research Center, Institute of Computing Technology, Chinese Academy of Sciences, 100190 Beijing, China
| | - Xin Gao
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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25
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Sabinina VJ, Hossain MJ, Hériché JK, Hoess P, Nijmeijer B, Mosalaganti S, Kueblbeck M, Callegari A, Szymborska A, Beck M, Ries J, Ellenberg J. Three-dimensional superresolution fluorescence microscopy maps the variable molecular architecture of the nuclear pore complex. Mol Biol Cell 2021; 32:1523-1533. [PMID: 34191541 PMCID: PMC8351745 DOI: 10.1091/mbc.e20-11-0728] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Nuclear pore complexes (NPCs) are large macromolecular machines that mediate the traffic between the nucleus and the cytoplasm. In vertebrates, each NPC consists of ∼1000 proteins, termed nucleoporins, and has a mass of more than 100 MDa. While a pseudo-atomic static model of the central scaffold of the NPC has recently been assembled by integrating data from isolated proteins and complexes, many structural components still remain elusive due to the enormous size and flexibility of the NPC. Here, we explored the power of three-dimensional (3D) superresolution microscopy combined with computational classification and averaging to explore the 3D structure of the NPC in single human cells. We show that this approach can build the first integrated 3D structural map containing both central as well as peripheral NPC subunits with molecular specificity and nanoscale resolution. Our unbiased classification of more than 10,000 individual NPCs indicates that the nuclear ring and the nuclear basket can adopt different conformations. Our approach opens up the exciting possibility to relate different structural states of the NPC to function in situ.
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Affiliation(s)
- Vilma Jimenez Sabinina
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - M Julius Hossain
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Jean-Karim Hériché
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Philipp Hoess
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Bianca Nijmeijer
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Shyamal Mosalaganti
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Moritz Kueblbeck
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Andrea Callegari
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anna Szymborska
- Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Martin Beck
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Jonas Ries
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Jan Ellenberg
- Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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26
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Structure of the mature Rous sarcoma virus lattice reveals a role for IP6 in the formation of the capsid hexamer. Nat Commun 2021; 12:3226. [PMID: 34050170 PMCID: PMC8163826 DOI: 10.1038/s41467-021-23506-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 05/03/2021] [Indexed: 02/08/2023] Open
Abstract
Inositol hexakisphosphate (IP6) is an assembly cofactor for HIV-1. We report here that IP6 is also used for assembly of Rous sarcoma virus (RSV), a retrovirus from a different genus. IP6 is ~100-fold more potent at promoting RSV mature capsid protein (CA) assembly than observed for HIV-1 and removal of IP6 in cells reduces infectivity by 100-fold. Here, visualized by cryo-electron tomography and subtomogram averaging, mature capsid-like particles show an IP6-like density in the CA hexamer, coordinated by rings of six lysines and six arginines. Phosphate and IP6 have opposing effects on CA in vitro assembly, inducing formation of T = 1 icosahedrons and tubes, respectively, implying that phosphate promotes pentamer and IP6 hexamer formation. Subtomogram averaging and classification optimized for analysis of pleomorphic retrovirus particles reveal that the heterogeneity of mature RSV CA polyhedrons results from an unexpected, intrinsic CA hexamer flexibility. In contrast, the CA pentamer forms rigid units organizing the local architecture. These different features of hexamers and pentamers determine the structural mechanism to form CA polyhedrons of variable shape in mature RSV particles.
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27
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Tremel S, Ohashi Y, Morado DR, Bertram J, Perisic O, Brandt LTL, von Wrisberg MK, Chen ZA, Maslen SL, Kovtun O, Skehel M, Rappsilber J, Lang K, Munro S, Briggs JAG, Williams RL. Structural basis for VPS34 kinase activation by Rab1 and Rab5 on membranes. Nat Commun 2021; 12:1564. [PMID: 33692360 PMCID: PMC7946940 DOI: 10.1038/s41467-021-21695-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 02/01/2021] [Indexed: 02/07/2023] Open
Abstract
The lipid phosphatidylinositol-3-phosphate (PI3P) is a regulator of two fundamental but distinct cellular processes, endocytosis and autophagy, so its generation needs to be under precise temporal and spatial control. PI3P is generated by two complexes that both contain the lipid kinase VPS34: complex II on endosomes (VPS34/VPS15/Beclin 1/UVRAG), and complex I on autophagosomes (VPS34/VPS15/Beclin 1/ATG14L). The endosomal GTPase Rab5 binds complex II, but the mechanism of VPS34 activation by Rab5 has remained elusive, and no GTPase is known to bind complex I. Here we show that Rab5a–GTP recruits endocytic complex II to membranes and activates it by binding between the VPS34 C2 and VPS15 WD40 domains. Electron cryotomography of complex II on Rab5a-decorated vesicles shows that the VPS34 kinase domain is released from inhibition by VPS15 and hovers over the lipid bilayer, poised for catalysis. We also show that the GTPase Rab1a, which is known to be involved in autophagy, recruits and activates the autophagy-specific complex I, but not complex II. Both Rabs bind to the same VPS34 interface but in a manner unique for each. These findings reveal how VPS34 complexes are activated on membranes by specific Rab GTPases and how they are recruited to unique cellular locations. The phosphatidylinositol-3-phosphate (PI3P) is generated by the lipid kinase VPS34, in the context of VPS34 complex I on autophagosomes or complex II on endosomes. Biochemical and structural analyses provide insights into the mechanism of both VPS34 complexes recruitment to and activation on membranes by specific Rab GTPases.
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Affiliation(s)
| | - Yohei Ohashi
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Dustin R Morado
- MRC Laboratory of Molecular Biology, Cambridge, UK.,Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | | | - Olga Perisic
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | | | - Marie-Kristin von Wrisberg
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Lab for Synthetic Biochemistry, Technical University of Munich, Institute for Advanced Study, TUM-IAS, Garching, Germany
| | - Zhuo A Chen
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | | | | | - Mark Skehel
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Juri Rappsilber
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany.,Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Kathrin Lang
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Lab for Synthetic Biochemistry, Technical University of Munich, Institute for Advanced Study, TUM-IAS, Garching, Germany
| | - Sean Munro
- MRC Laboratory of Molecular Biology, Cambridge, UK.
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28
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Leneva N, Kovtun O, Morado DR, Briggs JAG, Owen DJ. Architecture and mechanism of metazoan retromer:SNX3 tubular coat assembly. SCIENCE ADVANCES 2021; 7:7/13/eabf8598. [PMID: 33762348 PMCID: PMC7990337 DOI: 10.1126/sciadv.abf8598] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/05/2021] [Indexed: 05/12/2023]
Abstract
Retromer is a master regulator of cargo retrieval from endosomes, which is critical for many cellular processes including signaling, immunity, neuroprotection, and virus infection. The retromer core (VPS26/VPS29/VPS35) is present on cargo-transporting, tubular carriers along with a range of sorting nexins. Here, we elucidate the structural basis of membrane tubulation and coupled cargo recognition by metazoan and fungal retromer coats assembled with the non-Bin1/Amphiphysin/Rvs (BAR) sorting nexin SNX3 using cryo-electron tomography. The retromer core retains its arched, scaffolding structure but changes its mode of membrane recruitment when assembled with different SNX adaptors, allowing cargo recognition at subunit interfaces. Thus, membrane bending and cargo incorporation can be modulated to allow retromer to traffic cargoes along different cellular transport routes.
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Affiliation(s)
- Natalya Leneva
- Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Oleksiy Kovtun
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
| | - Dustin R Morado
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - John A G Briggs
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
| | - David J Owen
- Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.
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29
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Martins B, Sorrentino S, Chung WL, Tatli M, Medalia O, Eibauer M. Unveiling the polarity of actin filaments by cryo-electron tomography. Structure 2021; 29:488-498.e4. [PMID: 33476550 PMCID: PMC8111420 DOI: 10.1016/j.str.2020.12.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/04/2020] [Accepted: 12/23/2020] [Indexed: 01/01/2023]
Abstract
The actin cytoskeleton plays a fundamental role in numerous cellular processes, such as cell motility, cytokinesis, and adhesion to the extracellular matrix. Revealing the polarity of individual actin filaments in intact cells would foster an unprecedented understanding of cytoskeletal processes and their associated mechanical forces. Cryo-electron tomography provides the means for high-resolution structural imaging of cells. However, the low signal-to-noise ratio of cryo-tomograms obscures the high frequencies, and therefore the polarity of actin filaments cannot be directly measured. Here, we developed a method that enables us to determine the polarity of actin filaments in cellular cryo-tomograms. We applied it to reveal the actin polarity distribution in focal adhesions, and show a linear relation between actin polarity and distance from the apical boundary of the adhesion site. Determining the polarity of individual actin filaments inside cells Reconstruction of actin networks from cryo-tomograms The polarity of actin changes from mixed to uniform along focal adhesions
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Affiliation(s)
- Bruno Martins
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Simona Sorrentino
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Wen-Lu Chung
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Meltem Tatli
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Matthias Eibauer
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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30
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Schuller AP, Wojtynek M, Mankus D, Tatli M, Kronenberg-Tenga R, Regmi SG, Dip PV, Lytton-Jean AKR, Brignole EJ, Dasso M, Weis K, Medalia O, Schwartz TU. The cellular environment shapes the nuclear pore complex architecture. Nature 2021; 598:667-671. [PMID: 34646014 PMCID: PMC8550940 DOI: 10.1038/s41586-021-03985-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 09/01/2021] [Indexed: 12/04/2022]
Abstract
Nuclear pore complexes (NPCs) create large conduits for cargo transport between the nucleus and cytoplasm across the nuclear envelope (NE)1-3. These multi-megadalton structures are composed of about thirty different nucleoporins that are distributed in three main substructures (the inner, cytoplasmic and nucleoplasmic rings) around the central transport channel4-6. Here we use cryo-electron tomography on DLD-1 cells that were prepared using cryo-focused-ion-beam milling to generate a structural model for the human NPC in its native environment. We show that-compared with previous human NPC models obtained from purified NEs-the inner ring in our model is substantially wider; the volume of the central channel is increased by 75% and the nucleoplasmic and cytoplasmic rings are reorganized. Moreover, the NPC membrane exhibits asymmetry around the inner-ring complex. Using targeted degradation of Nup96, a scaffold nucleoporin of the cytoplasmic and nucleoplasmic rings, we observe the interdependence of each ring in modulating the central channel and maintaining membrane asymmetry. Our findings highlight the inherent flexibility of the NPC and suggest that the cellular environment has a considerable influence on NPC dimensions and architecture.
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Affiliation(s)
- Anthony P. Schuller
- grid.116068.80000 0001 2341 2786Department of Biology, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Matthias Wojtynek
- grid.7400.30000 0004 1937 0650Department of Biochemistry, University of Zurich, Zurich, Switzerland ,grid.5801.c0000 0001 2156 2780Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - David Mankus
- grid.116068.80000 0001 2341 2786Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Meltem Tatli
- grid.7400.30000 0004 1937 0650Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Rafael Kronenberg-Tenga
- grid.7400.30000 0004 1937 0650Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Saroj G. Regmi
- grid.94365.3d0000 0001 2297 5165Division of Molecular and Cellular Biology, National Institute of Child Health and Human Development, NIH, Bethesda, MD USA
| | - Phat V. Dip
- grid.116068.80000 0001 2341 2786Department of Biology, Massachusetts Institute of Technology, Cambridge, MA USA ,grid.116068.80000 0001 2341 2786MIT.nano, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Abigail K. R. Lytton-Jean
- grid.116068.80000 0001 2341 2786Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Edward J. Brignole
- grid.116068.80000 0001 2341 2786Department of Biology, Massachusetts Institute of Technology, Cambridge, MA USA ,grid.116068.80000 0001 2341 2786MIT.nano, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Mary Dasso
- grid.94365.3d0000 0001 2297 5165Division of Molecular and Cellular Biology, National Institute of Child Health and Human Development, NIH, Bethesda, MD USA
| | - Karsten Weis
- grid.5801.c0000 0001 2156 2780Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ohad Medalia
- grid.7400.30000 0004 1937 0650Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Thomas U. Schwartz
- grid.116068.80000 0001 2341 2786Department of Biology, Massachusetts Institute of Technology, Cambridge, MA USA
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31
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Leung MR, Zeev-Ben-Mordehai T. Cryo-electron microscopy of cholinesterases, present and future. J Neurochem 2020; 158:1236-1243. [PMID: 33222205 PMCID: PMC8518539 DOI: 10.1111/jnc.15245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 10/30/2020] [Accepted: 11/11/2020] [Indexed: 02/06/2023]
Abstract
Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) exist in a variety of oligomeric forms, each with defined cellular and subcellular distributions. Although crystal structures of AChE and BChE have been available for many years, structures of the physiologically relevant ChE tetramer were only recently solved by cryo‐electron microscopy (cryo‐EM) single‐particle analysis. Here, we briefly review how these structures contribute to our understanding of cholinesterase oligomerization, highlighting the advantages of using cryo‐EM to resolve structures of protein assemblies that cannot be expressed recombinantly. We argue that the next frontier in cholinesterase structural biology is to image membrane‐anchored ChE oligomers directly in their native environment—the cell.
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Affiliation(s)
- Miguel Ricardo Leung
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands.,The Division of Structural Biology, Wellcome Centre for Human Genetics, The University of Oxford, Oxford, UK
| | - Tzviya Zeev-Ben-Mordehai
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands.,The Division of Structural Biology, Wellcome Centre for Human Genetics, The University of Oxford, Oxford, UK
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32
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Turk M, Baumeister W. The promise and the challenges of cryo-electron tomography. FEBS Lett 2020; 594:3243-3261. [PMID: 33020915 DOI: 10.1002/1873-3468.13948] [Citation(s) in RCA: 137] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/28/2020] [Accepted: 09/28/2020] [Indexed: 01/11/2023]
Abstract
Structural biologists have traditionally approached cellular complexity in a reductionist manner in which the cellular molecular components are fractionated and purified before being studied individually. This 'divide and conquer' approach has been highly successful. However, awareness has grown in recent years that biological functions can rarely be attributed to individual macromolecules. Most cellular functions arise from their concerted action, and there is thus a need for methods enabling structural studies performed in situ, ideally in unperturbed cellular environments. Cryo-electron tomography (Cryo-ET) combines the power of 3D molecular-level imaging with the best structural preservation that is physically possible to achieve. Thus, it has a unique potential to reveal the supramolecular architecture or 'molecular sociology' of cells and to discover the unexpected. Here, we review state-of-the-art Cryo-ET workflows, provide examples of biological applications, and discuss what is needed to realize the full potential of Cryo-ET.
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Affiliation(s)
- Martin Turk
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
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33
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Turoňová B, Sikora M, Schürmann C, Hagen WJH, Welsch S, Blanc FEC, von Bülow S, Gecht M, Bagola K, Hörner C, van Zandbergen G, Landry J, de Azevedo NTD, Mosalaganti S, Schwarz A, Covino R, Mühlebach MD, Hummer G, Krijnse Locker J, Beck M. In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges. Science 2020; 370:203-208. [PMID: 32817270 DOI: 10.1101/2020.06.26.173476] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 08/13/2020] [Indexed: 05/24/2023]
Abstract
The spike protein (S) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is required for cell entry and is the primary focus for vaccine development. In this study, we combined cryo-electron tomography, subtomogram averaging, and molecular dynamics simulations to structurally analyze S in situ. Compared with the recombinant S, the viral S was more heavily glycosylated and occurred mostly in the closed prefusion conformation. We show that the stalk domain of S contains three hinges, giving the head unexpected orientational freedom. We propose that the hinges allow S to scan the host cell surface, shielded from antibodies by an extensive glycan coat. The structure of native S contributes to our understanding of SARS-CoV-2 infection and potentially to the development of safe vaccines.
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Affiliation(s)
- Beata Turoňová
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
- Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Mateusz Sikora
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Christoph Schürmann
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
| | - Wim J H Hagen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Florian E C Blanc
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Sören von Bülow
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Michael Gecht
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Katrin Bagola
- Division of Immunology, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
| | - Cindy Hörner
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
- German Center for Infection Research, Gießen-Marburg-Langen, Germany
| | - Ger van Zandbergen
- Division of Immunology, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
- Institute for Immunology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
- Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Jonathan Landry
- Genomics Core Facility, EMBL, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | | | - Shyamal Mosalaganti
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
- Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Andre Schwarz
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Roberto Covino
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
- Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main, Germany
| | - Michael D Mühlebach
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
- German Center for Infection Research, Gießen-Marburg-Langen, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany.
- Institute of Biophysics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Jacomine Krijnse Locker
- Electron Microscopy of Pathogens Unit, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany.
| | - Martin Beck
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany.
- Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
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34
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Wan W, Clarke M, Norris MJ, Kolesnikova L, Koehler A, Bornholdt ZA, Becker S, Saphire EO, Briggs JA. Ebola and Marburg virus matrix layers are locally ordered assemblies of VP40 dimers. eLife 2020; 9:59225. [PMID: 33016878 PMCID: PMC7588233 DOI: 10.7554/elife.59225] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 10/02/2020] [Indexed: 01/28/2023] Open
Abstract
Filoviruses such as Ebola and Marburg virus bud from the host membrane as enveloped virions. This process is achieved by the matrix protein VP40. When expressed alone, VP40 induces budding of filamentous virus-like particles, suggesting that localization to the plasma membrane, oligomerization into a matrix layer, and generation of membrane curvature are intrinsic properties of VP40. There has been no direct information on the structure of VP40 matrix layers within viruses or virus-like particles. We present structures of Ebola and Marburg VP40 matrix layers in intact virus-like particles, and within intact Marburg viruses. VP40 dimers assemble extended chains via C-terminal domain interactions. These chains stack to form 2D matrix lattices below the membrane surface. These lattices form a patchwork assembly across the membrane and suggesting that assembly may begin at multiple points. Our observations define the structure and arrangement of the matrix protein layer that mediates formation of filovirus particles.
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Affiliation(s)
- William Wan
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Mairi Clarke
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Michael J Norris
- Center for Infectious Disease and Vaccine Research, La Jolla Institute for Immunology, La Jolla, United States
| | - Larissa Kolesnikova
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Marburg, Germany
| | - Alexander Koehler
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Marburg, Germany
| | | | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Marburg, Germany
| | - Erica Ollmann Saphire
- Center for Infectious Disease and Vaccine Research, La Jolla Institute for Immunology, La Jolla, United States
| | - John Ag Briggs
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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35
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The native structure of the assembled matrix protein 1 of influenza A virus. Nature 2020; 587:495-498. [PMID: 32908308 DOI: 10.1038/s41586-020-2696-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/19/2020] [Indexed: 02/03/2023]
Abstract
Influenza A virus causes millions of severe cases of disease during annual epidemics. The most abundant protein in influenza virions is matrix protein 1 (M1), which mediates virus assembly by forming an endoskeleton beneath the virus membrane1. The structure of full-length M1, and how it oligomerizes to mediate the assembly of virions, is unknown. Here we determine the complete structure of assembled M1 within intact virus particles, as well as the structure of M1 oligomers reconstituted in vitro. We find that the C-terminal domain of M1 is disordered in solution but can fold and bind in trans to the N-terminal domain of another M1 monomer, thus polymerizing M1 into linear strands that coat the interior surface of the membrane of the assembling virion. In the M1 polymer, five histidine residues-contributed by three different monomers of M1-form a cluster that can serve as the pH-sensitive disassembly switch after entry into a target cell. These structures therefore reveal mechanisms of influenza virus assembly and disassembly.
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36
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Turoňová B, Sikora M, Schürmann C, Hagen WJH, Welsch S, Blanc FEC, von Bülow S, Gecht M, Bagola K, Hörner C, van Zandbergen G, Landry J, de Azevedo NTD, Mosalaganti S, Schwarz A, Covino R, Mühlebach MD, Hummer G, Krijnse Locker J, Beck M. In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges. Science 2020; 370:203-208. [PMID: 32817270 PMCID: PMC7665311 DOI: 10.1126/science.abd5223] [Citation(s) in RCA: 434] [Impact Index Per Article: 108.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 08/13/2020] [Indexed: 12/12/2022]
Abstract
The spike protein (S) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is required for cell entry and is the primary focus for vaccine development. In this study, we combined cryo-electron tomography, subtomogram averaging, and molecular dynamics simulations to structurally analyze S in situ. Compared with the recombinant S, the viral S was more heavily glycosylated and occurred mostly in the closed prefusion conformation. We show that the stalk domain of S contains three hinges, giving the head unexpected orientational freedom. We propose that the hinges allow S to scan the host cell surface, shielded from antibodies by an extensive glycan coat. The structure of native S contributes to our understanding of SARS-CoV-2 infection and potentially to the development of safe vaccines.
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Affiliation(s)
- Beata Turoňová
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany.,Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Mateusz Sikora
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Christoph Schürmann
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
| | - Wim J H Hagen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Florian E C Blanc
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Sören von Bülow
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Michael Gecht
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Katrin Bagola
- Division of Immunology, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany
| | - Cindy Hörner
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany.,German Center for Infection Research, Gießen-Marburg-Langen, Germany
| | - Ger van Zandbergen
- Division of Immunology, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany.,Institute for Immunology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany.,Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Jonathan Landry
- Genomics Core Facility, EMBL, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | | | - Shyamal Mosalaganti
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany.,Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
| | - Andre Schwarz
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Roberto Covino
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany.,Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main, Germany
| | - Michael D Mühlebach
- Division of Veterinary Medicine, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany.,German Center for Infection Research, Gießen-Marburg-Langen, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany. .,Institute of Biophysics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Jacomine Krijnse Locker
- Electron Microscopy of Pathogens Unit, Paul Ehrlich Institute, Paul Ehrlich Strasse 51-59, 63225 Langen, Germany.
| | - Martin Beck
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, 69117 Heidelberg, Germany. .,Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany
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37
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Structures and distributions of SARS-CoV-2 spike proteins on intact virions. Nature 2020; 588:498-502. [PMID: 32805734 DOI: 10.1038/s41586-020-2665-2] [Citation(s) in RCA: 760] [Impact Index Per Article: 190.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 08/10/2020] [Indexed: 02/06/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions are surrounded by a lipid bilayer from which spike (S) protein trimers protrude1. Heavily glycosylated S trimers bind to the angiotensin-converting enzyme 2 receptor and mediate entry of virions into target cells2-6. S exhibits extensive conformational flexibility: it modulates exposure of its receptor-binding site and subsequently undergoes complete structural rearrangement to drive fusion of viral and cellular membranes2,7,8. The structures and conformations of soluble, overexpressed, purified S proteins have been studied in detail using cryo-electron microscopy2,7,9-12, but the structure and distribution of S on the virion surface remain unknown. Here we applied cryo-electron microscopy and tomography to image intact SARS-CoV-2 virions and determine the high-resolution structure, conformational flexibility and distribution of S trimers in situ on the virion surface. These results reveal the conformations of S on the virion, and provide a basis from which to understand interactions between S and neutralizing antibodies during infection or vaccination.
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38
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Kovtun O, Dickson VK, Kelly BT, Owen DJ, Briggs JAG. Architecture of the AP2/clathrin coat on the membranes of clathrin-coated vesicles. SCIENCE ADVANCES 2020; 6:eaba8381. [PMID: 32743075 PMCID: PMC7375805 DOI: 10.1126/sciadv.aba8381] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 04/17/2020] [Indexed: 05/19/2023]
Abstract
Clathrin-mediated endocytosis (CME) is crucial for modulating the protein composition of a cell's plasma membrane. Clathrin forms a cage-like, polyhedral outer scaffold around a vesicle, to which cargo-selecting clathrin adaptors are attached. Adaptor protein complex (AP2) is the key adaptor in CME. Crystallography has shown AP2 to adopt a range of conformations. Here, we used cryo-electron microscopy, tomography, and subtomogram averaging to determine structures, interactions, and arrangements of clathrin and AP2 at the key steps of coat assembly, from AP2 in solution to membrane-assembled clathrin-coated vesicles (CCVs). AP2 binds cargo and PtdIns(4,5)P 2 (phosphatidylinositol 4,5-bisphosphate)-containing membranes via multiple interfaces, undergoing conformational rearrangement from its cytosolic state. The binding mode of AP2 β2 appendage into the clathrin lattice in CCVs and buds implies how the adaptor structurally modulates coat curvature and coat disassembly.
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Affiliation(s)
- Oleksiy Kovtun
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg , Germany
| | - Veronica Kane Dickson
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - Bernard T. Kelly
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
- Corresponding author. (B.T.K.); (D.J.O.); (J.A.G.B.)
| | - David J. Owen
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
- Corresponding author. (B.T.K.); (D.J.O.); (J.A.G.B.)
| | - John A. G. Briggs
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg , Germany
- Corresponding author. (B.T.K.); (D.J.O.); (J.A.G.B.)
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39
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Chakraborty S, Jasnin M, Baumeister W. Three-dimensional organization of the cytoskeleton: A cryo-electron tomography perspective. Protein Sci 2020; 29:1302-1320. [PMID: 32216120 PMCID: PMC7255506 DOI: 10.1002/pro.3858] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/17/2020] [Accepted: 03/20/2020] [Indexed: 01/01/2023]
Abstract
Traditionally, structures of cytoskeletal components have been studied ex situ, that is, with biochemically purified materials. There are compelling reasons to develop approaches to study them in situ in their native functional context. In recent years, cryo-electron tomography emerged as a powerful method for visualizing the molecular organization of unperturbed cellular landscapes with the potential to attain near-atomic resolution. Here, we review recent works on the cytoskeleton using cryo-electron tomography, demonstrating the power of in situ studies. We also highlight the potential of this method in addressing important questions pertinent to the field of cytoskeletal biomechanics.
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Affiliation(s)
- Saikat Chakraborty
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Marion Jasnin
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Wolfgang Baumeister
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
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40
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Sahu A, Glisman A, Tchoufag J, Mandadapu KK. Geometry and dynamics of lipid membranes: The Scriven-Love number. Phys Rev E 2020; 101:052401. [PMID: 32575240 DOI: 10.1103/physreve.101.052401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/07/2020] [Indexed: 06/11/2023]
Abstract
The equations governing lipid membrane dynamics in planar, spherical, and cylindrical geometries are presented here. Unperturbed and first-order perturbed equations are determined and nondimensionalized. In membrane systems with a nonzero base flow, perturbed in-plane and out-of-plane quantities are found to vary over different length scales. A new dimensionless number, named the Scriven-Love number, and the well-known Föppl-von Kármán number result from a scaling analysis. The Scriven-Love number compares out-of-plane forces arising from the in-plane, intramembrane viscous stresses to the familiar elastic bending forces, while the Föppl-von Kármán number compares tension to bending forces. Both numbers are calculated in past experimental works, and span a wide range of values in various biological processes across different geometries. In situations with large Scriven-Love and Föppl-von Kármán numbers, the dynamical response of a perturbed membrane is dominated by out-of-plane viscous and surface tension forces-with bending forces playing a negligible role. Calculations of non-negligible Scriven-Love numbers in various biological processes and in vitro experiments show in-plane intramembrane viscous flows cannot generally be ignored when analyzing lipid membrane behavior.
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Affiliation(s)
- Amaresh Sahu
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Alec Glisman
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Joël Tchoufag
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Kranthi K Mandadapu
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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41
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Benchmarking tomographic acquisition schemes for high-resolution structural biology. Nat Commun 2020; 11:876. [PMID: 32054835 PMCID: PMC7018747 DOI: 10.1038/s41467-020-14535-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 01/16/2020] [Indexed: 12/25/2022] Open
Abstract
Cryo electron tomography with subsequent subtomogram averaging is a powerful technique to structurally analyze macromolecular complexes in their native context. Although close to atomic resolution in principle can be obtained, it is not clear how individual experimental parameters contribute to the attainable resolution. Here, we have used immature HIV-1 lattice as a benchmarking sample to optimize the attainable resolution for subtomogram averaging. We systematically tested various experimental parameters such as the order of projections, different angular increments and the use of the Volta phase plate. We find that although any of the prominently used acquisition schemes is sufficient to obtain subnanometer resolution, dose-symmetric acquisition provides considerably better outcome. We discuss our findings in order to provide guidance for data acquisition. Our data is publicly available and might be used to further develop processing routines. Here the authors systematically benchmark cryo-electron tomography acquisition schemes to optimize the attainable resolution for subtomogram averaging, and find that dose-symmetric acquisition with even angular sampling provides a better outcome than most currently used acquisition schemes.
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42
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Dick RA, Xu C, Morado DR, Kravchuk V, Ricana CL, Lyddon TD, Broad AM, Feathers JR, Johnson MC, Vogt VM, Perilla JR, Briggs JAG, Schur FKM. Structures of immature EIAV Gag lattices reveal a conserved role for IP6 in lentivirus assembly. PLoS Pathog 2020; 16:e1008277. [PMID: 31986188 PMCID: PMC7004409 DOI: 10.1371/journal.ppat.1008277] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 02/06/2020] [Accepted: 12/11/2019] [Indexed: 01/11/2023] Open
Abstract
Retrovirus assembly is driven by the multidomain structural protein Gag. Interactions between the capsid domains (CA) of Gag result in Gag multimerization, leading to an immature virus particle that is formed by a protein lattice based on dimeric, trimeric, and hexameric protein contacts. Among retroviruses the inter- and intra-hexamer contacts differ, especially in the N-terminal sub-domain of CA (CANTD). For HIV-1 the cellular molecule inositol hexakisphosphate (IP6) interacts with and stabilizes the immature hexamer, and is required for production of infectious virus particles. We have used in vitro assembly, cryo-electron tomography and subtomogram averaging, atomistic molecular dynamics simulations and mutational analyses to study the HIV-related lentivirus equine infectious anemia virus (EIAV). In particular, we sought to understand the structural conservation of the immature lentivirus lattice and the role of IP6 in EIAV assembly. Similar to HIV-1, IP6 strongly promoted in vitro assembly of EIAV Gag proteins into virus-like particles (VLPs), which took three morphologically highly distinct forms: narrow tubes, wide tubes, and spheres. Structural characterization of these VLPs to sub-4Å resolution unexpectedly showed that all three morphologies are based on an immature lattice with preserved key structural components, highlighting the structural versatility of CA to form immature assemblies. A direct comparison between EIAV and HIV revealed that both lentiviruses maintain similar immature interfaces, which are established by both conserved and non-conserved residues. In both EIAV and HIV-1, IP6 regulates immature assembly via conserved lysine residues within the CACTD and SP. Lastly, we demonstrate that IP6 stimulates in vitro assembly of immature particles of several other retroviruses in the lentivirus genus, suggesting a conserved role for IP6 in lentiviral assembly.
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MESH Headings
- Amino Acid Sequence
- Animals
- Electron Microscope Tomography
- Equine Infectious Anemia/metabolism
- Equine Infectious Anemia/virology
- Gene Products, gag/chemistry
- Gene Products, gag/genetics
- Gene Products, gag/metabolism
- HIV Infections/metabolism
- HIV Infections/virology
- HIV-1/genetics
- HIV-1/physiology
- HIV-1/ultrastructure
- Horses
- Host-Pathogen Interactions
- Infectious Anemia Virus, Equine/chemistry
- Infectious Anemia Virus, Equine/genetics
- Infectious Anemia Virus, Equine/physiology
- Infectious Anemia Virus, Equine/ultrastructure
- Phytic Acid/metabolism
- Sequence Alignment
- Virion/genetics
- Virion/physiology
- Virion/ultrastructure
- Virus Assembly
- gag Gene Products, Human Immunodeficiency Virus/chemistry
- gag Gene Products, Human Immunodeficiency Virus/genetics
- gag Gene Products, Human Immunodeficiency Virus/metabolism
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Affiliation(s)
- Robert A. Dick
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
- * E-mail: (RAD); (FKMS)
| | - Chaoyi Xu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
| | - Dustin R. Morado
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Clifton L. Ricana
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, United States of America
| | - Terri D. Lyddon
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, United States of America
| | - Arianna M. Broad
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - J. Ryan Feathers
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Marc C. Johnson
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, United States of America
| | - Volker M. Vogt
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Juan R. Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States of America
| | - John A. G. Briggs
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Florian K. M. Schur
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- * E-mail: (RAD); (FKMS)
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43
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Template-free detection and classification of membrane-bound complexes in cryo-electron tomograms. Nat Methods 2020; 17:209-216. [PMID: 31907446 DOI: 10.1038/s41592-019-0675-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 11/11/2019] [Indexed: 01/12/2023]
Abstract
With faithful sample preservation and direct imaging of fully hydrated biological material, cryo-electron tomography provides an accurate representation of molecular architecture of cells. However, detection and precise localization of macromolecular complexes within cellular environments is aggravated by the presence of many molecular species and molecular crowding. We developed a template-free image processing procedure for accurate tracing of complex networks of densities in cryo-electron tomograms, a comprehensive and automated detection of heterogeneous membrane-bound complexes and an unsupervised classification (PySeg). Applications to intact cells and isolated endoplasmic reticulum (ER) allowed us to detect and classify small protein complexes. This classification provided sufficiently homogeneous particle sets and initial references to allow subsequent de novo subtomogram averaging. Spatial distribution analysis showed that ER complexes have different localization patterns forming nanodomains. Therefore, this procedure allows a comprehensive detection and structural analysis of complexes in situ.
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44
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Intact Viral Particle Counts Measured by Flow Virometry Provide Insight into the Infectivity and Genome Packaging Efficiency of Moloney Murine Leukemia Virus. J Virol 2020; 94:JVI.01600-19. [PMID: 31694951 DOI: 10.1128/jvi.01600-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 10/22/2019] [Indexed: 02/06/2023] Open
Abstract
Murine leukemia viruses (MLVs) have long been used as a research model to further our understanding of retroviruses. These simple gammaretroviruses have been studied extensively in various facets of science for nearly half a century, yet we have surprisingly little quantitative information about some of the basic features of these viral particles. These include parameters such as the genome packaging efficiency and the number of particles required for a productive infection. The reason for this knowledge gap relies primarily on the technical challenge of accurately measuring intact viral particles from infected cell supernatants. Virus-infected cells are well known to release soluble viral proteins, defective viruses, and extracellular vesicles (EVs) harboring viral proteins that may mimic viruses, all of which can skew virus titer quantifications. Flow virometry, also known as nanoscale flow cytometry or simply small-particle flow cytometry, is an emerging analytical method enabling high-throughput single-virus phenotypic characterizations. By utilizing the viral envelope glycoprotein (Env) and monodisperse light scattering characteristics as discerning parameters of intact virus particles, here, we analyzed the basic properties of Moloney MLV (M-MLV). We show that <24% of the total p30 capsid protein measured in infected cell supernatants is associated with intact viruses. We calculate that about one in five M-MLV particles contains a viral RNA genome pair and that individual intact particle infectivity is about 0.4%. These findings provide new insights into the characteristics of an extensively studied prototypical retrovirus while highlighting the benefits of flow virometry for the field of virology.IMPORTANCE Gammaretroviruses, or, more specifically, murine leukemia viruses (MLVs), have been a longstanding model for studying retroviruses. Although being extensively analyzed and dissected for decades, several facets of MLV biology are still poorly understood. One of the primary challenges has been enumerating total intact virus particles in a sample. While several analytical methods can precisely measure virus protein amounts, MLVs are known to induce the secretion of soluble and vesicle-associated viral proteins that can skew these measurements. With recent technological advances in flow cytometry, it is now possible to analyze viruses down to 90 nm in diameter with an approach called flow virometry. The technique has the added benefit of being able to discriminate viruses from extracellular vesicles and free viral proteins in order to confidently provide an intact viral particle count. Here, we used flow virometry to provide new insights into the basic characteristics of Moloney MLV.
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45
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Brittain GC, Chen YQ, Martinez E, Tang VA, Renner TM, Langlois MA, Gulnik S. A Novel Semiconductor-Based Flow Cytometer with Enhanced Light-Scatter Sensitivity for the Analysis of Biological Nanoparticles. Sci Rep 2019; 9:16039. [PMID: 31690751 PMCID: PMC6831566 DOI: 10.1038/s41598-019-52366-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 10/15/2019] [Indexed: 01/20/2023] Open
Abstract
The CytoFLEX is a novel semiconductor-based flow cytometer that utilizes avalanche photodiodes, wavelength-division multiplexing, enhanced optics, and diode lasers to maximize light capture and minimize optical and electronic noise. Due to an increasing interest in the use of extracellular vesicles (EVs) as disease biomarkers, and the growing desire to use flow cytometry for the analyses of biological nanoparticles, we assessed the light-scatter sensitivity of the CytoFLEX for small-particle detection. We found that the CytoFLEX can fully resolve 70 nm polystyrene and 98.6 nm silica beads by violet side scatter (VSSC). We further analyzed the detection limit for biological nanoparticles, including viruses and EVs, and show that the CytoFLEX can detect viruses down to 81 nm and EVs at least as small as 65 nm. Moreover, we could immunophenotype EV surface antigens, including directly in blood and plasma, demonstrating the double labeling of platelet EVs with CD61 and CD9, as well as triple labeling with CD81 for an EV subpopulation in one donor. In order to assess the refractive indices (RIs) of the viruses and EVs, we devised a new method to inversely calculate the RIs using the intensity vs. size data together with Mie-theory scatter efficiencies scaled to reference-particle measurements. Each of the viruses tested had an equivalent RI, approximately 1.47 at 405 nm, which suggests that flow cytometry can be more broadly used to easily determine virus sizes. We also found that the RIs of EVs increase as the particle diameters decrease below 150 nm, increasing from 1.37 for 200 nm EVs up to 1.61 for 65 nm EVs, expanding the lower range of EVs that can be detected by light scatter. Overall, we demonstrate that the CytoFLEX has an unprecedented level of sensitivity compared to conventional flow cytometers. Accordingly, the CytoFLEX can be of great benefit to virology and EV research, and will help to expand the use of flow cytometry for minimally invasive liquid biopsies by allowing for the direct analysis of antigen expression on biological nanoparticles within patient samples, including blood, plasma, urine and bronchoalveolar lavages.
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Affiliation(s)
- George C Brittain
- Beckman Coulter Life Sciences, Life Science Research, Miami, FL, USA
| | - Yong Q Chen
- Beckman Coulter Life Sciences, Life Science Research, Miami, FL, USA
| | - Edgar Martinez
- Beckman Coulter Life Sciences, Particle Characterization, Miami, FL, USA
| | - Vera A Tang
- University of Ottawa Flow Cytometry and Virometry Core Facility, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Canada
| | - Tyler M Renner
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Canada
| | - Marc-André Langlois
- University of Ottawa Flow Cytometry and Virometry Core Facility, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Canada.,uOttawa Center for Infection, Immunity and Inflammation (CI3), University of Ottawa, Ottawa, Canada
| | - Sergei Gulnik
- Beckman Coulter Life Sciences, Life Science Research, Miami, FL, USA.
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46
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Obr M, Schur FKM. Structural analysis of pleomorphic and asymmetric viruses using cryo-electron tomography and subtomogram averaging. Adv Virus Res 2019; 105:117-159. [PMID: 31522703 DOI: 10.1016/bs.aivir.2019.07.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Describing the protein interactions that form pleomorphic and asymmetric viruses represents a considerable challenge to most structural biology techniques, including X-ray crystallography and single particle cryo-electron microscopy. Obtaining a detailed understanding of these interactions is nevertheless important, considering the number of relevant human pathogens that do not follow strict icosahedral or helical symmetry. Cryo-electron tomography and subtomogram averaging methods provide structural insights into complex biological environments and are well suited to go beyond structures of perfectly symmetric viruses. This chapter discusses recent developments showing that cryo-ET and subtomogram averaging can provide high-resolution insights into hitherto unknown structural features of pleomorphic and asymmetric virus particles. It also describes how these methods have significantly added to our understanding of retrovirus capsid assemblies in immature and mature viruses. Additional examples of irregular viruses and their associated proteins, whose structures have been studied via cryo-ET and subtomogram averaging, further support the versatility of these methods.
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Affiliation(s)
- Martin Obr
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Florian K M Schur
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria.
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47
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Stass R, Ng WM, Kim YC, Huiskonen JT. Structures of enveloped virions determined by cryogenic electron microscopy and tomography. Adv Virus Res 2019; 105:35-71. [PMID: 31522708 PMCID: PMC7112279 DOI: 10.1016/bs.aivir.2019.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Enveloped viruses enclose their genomes inside a lipid bilayer which is decorated by membrane proteins that mediate virus entry. These viruses display a wide range of sizes, morphologies and symmetries. Spherical viruses are often isometric and their envelope proteins follow icosahedral symmetry. Filamentous and pleomorphic viruses lack such global symmetry but their surface proteins may display locally ordered assemblies. Determining the structures of enveloped viruses, including the envelope proteins and their protein-protein interactions on the viral surface, is of paramount importance. These structures can reveal how the virions are assembled and released by budding from the infected host cell, how the progeny virions infect new cells by membrane fusion, and how antibodies bind surface epitopes to block infection. In this chapter, we discuss the uses of cryogenic electron microscopy (cryo-EM) in elucidating structures of enveloped virions. Starting from a detailed outline of data collection and processing strategies, we highlight how cryo-EM has been successfully utilized to provide unique insights into enveloped virus entry, assembly, and neutralization.
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Affiliation(s)
- Robert Stass
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Weng M Ng
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Young Chan Kim
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Juha T Huiskonen
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom; Helsinki Institute of Life Science HiLIFE and Research Programme in Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
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48
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VIPP1 rods engulf membranes containing phosphatidylinositol phosphates. Sci Rep 2019; 9:8725. [PMID: 31217458 PMCID: PMC6584618 DOI: 10.1038/s41598-019-44259-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Accepted: 05/14/2019] [Indexed: 12/15/2022] Open
Abstract
In cyanobacteria and plants, VIPP1 plays crucial roles in the biogenesis and repair of thylakoid membrane protein complexes and in coping with chloroplast membrane stress. In chloroplasts, VIPP1 localizes in distinct patterns at or close to envelope and thylakoid membranes. In vitro, VIPP1 forms higher-order oligomers of >1 MDa that organize into rings and rods. However, it remains unknown how VIPP1 oligomerization is related to function. Using time-resolved fluorescence anisotropy and sucrose density gradient centrifugation, we show here that Chlamydomonas reinhardtii VIPP1 binds strongly to liposomal membranes containing phosphatidylinositol-4-phosphate (PI4P). Cryo-electron tomography reveals that VIPP1 oligomerizes into rods that can engulf liposomal membranes containing PI4P. These findings place VIPP1 into a group of membrane-shaping proteins including epsin and BAR domain proteins. Moreover, they point to a potential role of phosphatidylinositols in directing the shaping of chloroplast membranes.
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Abstract
Cryo-electron tomography (cryo-ET) allows three-dimensional (3D) visualization of frozen-hydrated biological samples, such as protein complexes and cell organelles, in near-native environments at nanometer scale. Protein complexes that are present in multiple copies in a set of tomograms can be extracted, mutually aligned, and averaged to yield a signal-enhanced 3D structure up to sub-nanometer or even near-atomic resolution. This technique, called subtomogram averaging (StA), is powered by improvements in EM hardware and image processing software. Importantly, StA provides unique biological insights into the structure and function of cellular machinery in close-to-native contexts. In this chapter, we describe the principles and key steps of StA. We briefly cover sample preparation and data collection with an emphasis on image processing procedures related to tomographic reconstruction, subtomogram alignment, averaging, and classification. We conclude by summarizing current limitations and future directions of this technique with a focus on high-resolution StA.
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Markova EA, Zanetti G. Visualizing membrane trafficking through the electron microscope: cryo-tomography of coat complexes. Acta Crystallogr D Struct Biol 2019; 75:467-474. [PMID: 31063149 PMCID: PMC6503763 DOI: 10.1107/s2059798319005011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 04/12/2019] [Indexed: 11/23/2022] Open
Abstract
Coat proteins mediate vesicular transport between intracellular compartments, which is essential for the distribution of molecules within the eukaryotic cell. The global arrangement of coat proteins on the membrane is key to their function, and cryo-electron tomography and subtomogram averaging have been used to study membrane-bound coat proteins, providing crucial structural insight. This review outlines a workflow for the structural elucidation of coat proteins, incorporating recent developments in the collection and processing of cryo-electron tomography data. Recent work on coat protein I, coat protein II and retromer performed on in vitro reconstitutions or in situ is summarized. These studies have answered long-standing questions regarding the mechanisms of membrane binding, polymerization and assembly regulation of coat proteins.
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Affiliation(s)
- Evgenia A. Markova
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, England
| | - Giulia Zanetti
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, England
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