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Seitz S, Habjanič J, Schütz AK, Bartenschlager R. The Hepatitis B Virus Envelope Proteins: Molecular Gymnastics Throughout the Viral Life Cycle. Annu Rev Virol 2020; 7:263-288. [PMID: 32600157 DOI: 10.1146/annurev-virology-092818-015508] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
New hepatitis B virions released from infected hepatocytes are the result of an intricate maturation process that starts with the formation of the nucleocapsid providing a confined space where the viral DNA genome is synthesized via reverse transcription. Virion assembly is finalized by the enclosure of the icosahedral nucleocapsid within a heterogeneous envelope. The latter contains integral membrane proteins of three sizes, collectively known as hepatitis B surface antigen, and adopts multiple conformations in the course of the viral life cycle. The nucleocapsid conformation depends on the reverse transcription status of the genome, which in turn controls nucleocapsid interaction with the envelope proteins for virus exit. In addition, after secretion the virions undergo a distinct maturation step during which a topological switch of the large envelope protein confers infectivity. Here we review molecular determinants for envelopment and models that postulate molecular signals encoded in the capsid scaffold conducive or adverse to the recruitment of envelope proteins.
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Affiliation(s)
- Stefan Seitz
- Department of Infectious Diseases, University of Heidelberg, 69120 Heidelberg, Germany;
| | - Jelena Habjanič
- Bavarian NMR Center, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Anne K Schütz
- Bavarian NMR Center, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Ralf Bartenschlager
- Department of Infectious Diseases, University of Heidelberg, 69120 Heidelberg, Germany; .,Division of Virus-Associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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Li X, Zhou N, Chen W, Zhu B, Wang X, Xu B, Wang J, Liu H, Cheng L. Near-Atomic Resolution Structure Determination of a Cypovirus Capsid and Polymerase Complex Using Cryo-EM at 200kV. J Mol Biol 2016; 429:79-87. [PMID: 27914893 DOI: 10.1016/j.jmb.2016.11.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 11/15/2016] [Accepted: 11/26/2016] [Indexed: 12/23/2022]
Abstract
Single-particle cryo-electron microscopy (cryo-EM) allows the high-resolution structural determination of biological assemblies in a near-native environment. However, all high-resolution (better than 3.5Å) cryo-EM structures reported to date were obtained by using 300kV transmission electron microscopes (TEMs). We report here the structures of a cypovirus capsid of 750-Å diameter at 3.3-Å resolution and of RNA-dependent RNA polymerase (RdRp) complexes within the capsid at 3.9-Å resolution using a 200-kV TEM. The newly resolved structure revealed conformational changes of two subdomains in the RdRp. These conformational changes, which were involved in RdRp's switch from non-transcribing to transcribing mode, suggest that the RdRp may facilitate the unwinding of genomic double-stranded RNA. The possibility of 3-Å resolution structural determinations for biological assemblies of relatively small sizes using cryo-EM at 200kV was discussed.
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Affiliation(s)
- Xiaowu Li
- College of Physics and Information Science, Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan, 410081, China; Technology Center for Protein Sciences, Tsinghua University, Beijing, 100084, China
| | - Niyun Zhou
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Wenyuan Chen
- College of Physics and Information Science, Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan, 410081, China
| | - Bin Zhu
- College of Physics and Information Science, Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan, 410081, China
| | - Xurong Wang
- College of Physics and Information Science, Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan, 410081, China
| | - Bin Xu
- Technology Center for Protein Sciences, Tsinghua University, Beijing, 100084, China
| | - Jiawei Wang
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Hongrong Liu
- College of Physics and Information Science, Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan, 410081, China.
| | - Lingpeng Cheng
- Technology Center for Protein Sciences, Tsinghua University, Beijing, 100084, China; School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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Rosenthal PB. From high symmetry to high resolution in biological electron microscopy: a commentary on Crowther (1971) 'Procedures for three-dimensional reconstruction of spherical viruses by Fourier synthesis from electron micrographs'. Philos Trans R Soc Lond B Biol Sci 2015; 370:rstb.2014.0345. [PMID: 25750240 PMCID: PMC4360125 DOI: 10.1098/rstb.2014.0345] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Elucidation of the structure of biological macromolecules and larger assemblies has been essential to understanding the roles they play in living processes. Methods for three-dimensional structure determination of biological assemblies from images recorded in the electron microscope were therefore a key development. In his paper published in Philosophical Transactions B in 1971, Crowther described new computational procedures applied to the first three-dimensional reconstruction of an icosahedral virus from images of virus particles preserved in negative stain. The method for determining the relative orientation of randomly oriented particles and combining their images for reconstruction exploited the high symmetry of the virus particle. Computational methods for image analysis have since been extended to include biological assemblies without symmetry. Further experimental advances, combined with image analysis, have led to the method of cryomicroscopy, which is now used by structural biologists to study the structure and dynamics of biological machines and assemblies in atomic detail. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.
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Affiliation(s)
- Peter B Rosenthal
- Division of Physical Biochemistry, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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Abstract
With fast progresses in instrumentation, image processing algorithms, and computational resources, single particle electron cryo-microscopy (cryo-EM) 3-D reconstruction of icosahedral viruses has now reached near-atomic resolutions (3-4 Å). With comparable resolutions and more predictable outcomes, cryo-EM is now considered a preferred method over X-ray crystallography for determination of atomic structure of icosahedral viruses. At near-atomic resolutions, all-atom models or backbone models can be reliably built that allow residue level understanding of viral assembly and conformational changes among different stages of viral life cycle. With the developments of asymmetric reconstruction, it is now possible to visualize the complete structure of a complex virus with not only its icosahedral shell but also its multiple non-icosahedral structural features. In this chapter, we will describe single particle cryo-EM experimental and computational procedures for both near-atomic resolution reconstruction of icosahedral viruses and asymmetric reconstruction of viruses with both icosahedral and non-icosahedral structure components. Procedures for rigorous validation of the reconstructions and resolution evaluations using truly independent de novo initial models and refinements are also introduced.
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Affiliation(s)
- Fei Guo
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA
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Conventional electron microscopy, cryo-electron microscopy and cryo-electron tomography of viruses. Subcell Biochem 2013; 68:79-115. [PMID: 23737049 DOI: 10.1007/978-94-007-6552-8_3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Electron microscopy (EM) techniques have been crucial for understanding the structure of biological specimens such as cells, tissues and macromolecular assemblies. Viruses and related viral assemblies are ideal targets for structural studies that help to define essential biological functions. Whereas conventional EM methods use chemical fixation, dehydration, and staining of the specimens, cryo-electron microscopy (cryo-EM) preserves the native hydrated state. Combined with image processing and three-dimensional reconstruction techniques, cryo-EM provides 3D maps of these macromolecular complexes from projection images, at subnanometer to near-atomic resolutions. Cryo-EM is also a major technique in structural biology for dynamic studies of functional complexes, which are often unstable, flexible, scarce or transient in their native environments. As a tool, cryo-EM complements high-resolution techniques such as X-ray diffraction and NMR spectroscopy; these synergistic hybrid approaches provide important new information. Three-dimensional cryo-electron tomography goes further, and allows the study of viruses not only in their physiological state, but also in their natural environment in the cell, thereby bridging structural studies at the molecular and cellular levels.
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Thomas JM. From 2-D to 3-D to 4-D electron microscopy: an outline of the essence and promise of unconventional crystallography and spectroscopy. CRYSTALLOGR REV 2011. [DOI: 10.1080/0889311x.2010.535207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Lamarre B, Ryadnov MG. Self-assembling viral mimetics: one long journey with short steps. Macromol Biosci 2010; 11:503-13. [PMID: 21165940 DOI: 10.1002/mabi.201000330] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Indexed: 12/14/2022]
Abstract
Recently, the Foresight Institute has pronounced six economic challenges that can be addressed through the progress of nanotechnology. One of these is the health and longevity of human life. Amongst applications anticipated to provide a solution to this challenge, gene therapy appears to be particularly promising. In theory, many diseases that result from genetic disorders can be cured by correcting defective genes. In practice, finding efficient and safe delivery vectors remains the stumbling point on the path of genetic therapies to the clinic. Viruses, otherwise the most efficient transfectors, pose safety concerns over immune reactions, whereas synthetic gene packages greatly lack the structural integrity of viruses. An ideal vector is therefore seen as a compromise between the two: a nanoscale device, which would mimic a virus and act as a virus, but would do this at the designer's whim. A strategy to achieve this is offered by the virus architecture itself, the principles of which are translated into the function via exquisitely reproducible self-assembly mechanisms. Thus, to mimic a virus is to mimic the way it is built, i.e., self-assembly. With just a few attempts made so far, the journey to an artificial virus has had a short lifetime, but the promise it holds is not expected to reduce any time soon.
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Affiliation(s)
- Baptiste Lamarre
- National Physical Laboratory, Teddington, Middlesex, TW110LW, UK
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Zewail AH. Micrographia of the twenty-first century: from camera obscura to 4D microscopy. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2010; 368:1191-204. [PMID: 20123754 PMCID: PMC3263811 DOI: 10.1098/rsta.2009.0265] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper, the evolutionary and revolutionary developments of microscopic imaging are overviewed with a perspective on origins. From Alhazen's camera obscura, to Hooke and van Leeuwenhoek's two-dimensional optical micrography, and on to three- and four-dimensional (4D) electron microscopy, these developments over a millennium have transformed humans' scope of visualization. The changes in the length and time scales involved are unimaginable, beginning with the visible shadows of candles at the centimetre and second scales, and ending with invisible atoms with space and time dimensions of sub-nanometre and femtosecond. With these advances it has become possible to determine the structures of matter and to observe their elementary dynamics as they unfold in real time. Such observations provide the means for visualizing materials behaviour and biological function, with the aim of understanding emergent phenomena in complex systems.
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Affiliation(s)
- Ahmed H Zewail
- Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
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Crowther RA. From envelopes to atoms: The remarkable progress of biological electron microscopy. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2010; 81:1-32. [PMID: 21115171 DOI: 10.1016/b978-0-12-381357-2.00001-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The electron microscope has, in principle, provided a powerful method for investigating biological structures for quite sometime, but only recently is its full potential being realized. Technical advances in the microscopes themselves, in methods of specimen preparation, and in computer processing of the recorded micrographs have all been necessary to underpin progress. It is now possible with suitable unstained specimens of two-dimensional crystals, helical or tubular structures, and icosahedral viruses to achieve resolutions of 4Å or better. For nonsymmetrical particles, sub-nanometer resolution is often possible. Tomography is enabling detailed pictures of subcellular organization to be produced. Thus, electron microscopy is now starting to rival X-ray crystallography in the resolution achievable but with the advantage of being applicable to a far wider range of biological specimens. With further improvements already under way, electron microscopy is set to be a centrally important technique for understanding biological structure and function at all levels-from atomic to cellular.
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Affiliation(s)
- R Anthony Crowther
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
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