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Kelly DF. Liquid-Electron Microscopy and the Real-Time Revolution. Annu Rev Biophys 2025; 54:1-15. [PMID: 40327441 DOI: 10.1146/annurev-biophys-071624-095107] [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] [Indexed: 05/08/2025]
Abstract
Advances in imaging technology enable striking views of life's most minute details. A missing piece of the puzzle, however, is the direct atomic observation of biomolecules in action. Liquid-phase transmission electron microscopy (liquid-EM) is the room-temperature correlate to cryo-electron microscopy, which is leading the resolution revolution in biophysics. This article reviews current challenges and opportunities in the liquid-EM field while discussing technical considerations for specimen enclosures, devices and systems, and scientific data management. Since liquid-EM is gaining traction in the life sciences community, cross talk among the disciplines of materials and life sciences is needed to disseminate knowledge of best practices along with high-level user engagement. How liquid-EM technology is inspiring the real-time revolution in molecular microscopy is also discussed. Looking ahead, the new movement can be better supported through open resource sharing and partnerships among academic, industry, and federal organizations, which may benefit from the scientific equity foundational to the technique.
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Navarro PP, Vettiger A, Hajdu R, Ananda VY, López-Tavares A, Schmid EW, Walter JC, Loose M, Chao LH, Bernhardt TG. The aPBP-type cell wall synthase PBP1b plays a specialized role in fortifying the Escherichia coli division site against osmotic rupture. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.04.02.646830. [PMID: 40236067 PMCID: PMC11996507 DOI: 10.1101/2025.04.02.646830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 04/17/2025]
Abstract
A multi-protein system called the divisome promotes bacterial division. This apparatus synthesizes the peptidoglycan (PG) cell wall layer that forms the daughter cell poles and protects them from osmotic lysis. In the model Gram-negative bacterium Escherichia coli , PG synthases called class A penicillin-binding proteins (aPBPs) have been proposed to play crucial roles in division. However, there is limited experimental support for aPBPs playing a specialized role in division that is distinct from their general function in the expansion and fortification of the PG matrix. Here, we present in situ cryogenic electron tomography data indicating that the aPBP-type enzyme PBP1b is required to produce a wedge-like density of PG at the division site. Furthermore, atomic force and live cell microscopy showed that loss of this structure weakens the division site and renders it susceptible to lysis. Surprisingly, we found that the lipoprotein activator LpoB needed to promote the general function of PBP1b was not required for normal division site architecture or its integrity. Additionally, we show that of the two PBP1b isoforms produced in cells, it is the one with an extended cytoplasmic N-terminus that functions in division, likely via recruitment by the FtsA component of the divisome. Altogether, our results demonstrate that PBP1b plays a specialized, LpoB-independent role in E. coli cell division involving the biogenesis of a PG structure that prevents osmotic rupture. The conservation of aPBPs with extended cytoplasmic N-termini suggests that other Gram-negative bacteria may use similar mechanisms to reinforce their division site.
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McArthur SJ, Umeda K, Kodera N. Nano-Scale Video Imaging of Motility Machinery by High-Speed Atomic Force Microscopy. Biomolecules 2025; 15:257. [PMID: 40001560 PMCID: PMC11852755 DOI: 10.3390/biom15020257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2025] [Revised: 02/05/2025] [Accepted: 02/06/2025] [Indexed: 02/27/2025] Open
Abstract
Motility is a vital aspect of many forms of life, with a wide range of highly conserved as well as highly unique systems adapted to the needs of various organisms and environments. While many motility systems are well studied using structural techniques like X-ray crystallography and electron microscopy, as well as fluorescence microscopy methodologies, it is difficult to directly determine the relationship between the shape and movement of a motility system due to a notable gap in spatiotemporal resolution. Bridging this gap as well as understanding the dynamic molecular movements that underpin motility mechanisms has been challenging. The advent of high-speed atomic force microscopy (HS-AFM) has provided a new window into understanding these nano-scale machines and the dynamic processes underlying motility. In this review, we highlight some of the advances in this field, ranging from reconstituted systems and purified higher-order supramolecular complexes to live cells, in both prokaryotic and eukaryotic contexts.
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Affiliation(s)
- Steven John McArthur
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan;
| | - Kenichi Umeda
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan;
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan and Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Noriyuki Kodera
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan;
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4
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Hirakis SP, Bartol TM, Autin L, Amaro RE, Sejnowski TJ. Electrophysical cardiac remodeling at the molecular level: Insights into ryanodine receptor activation and calcium-induced calcium release from a stochastic explicit-particle model. Biophys J 2024; 123:3812-3831. [PMID: 39369273 PMCID: PMC11560313 DOI: 10.1016/j.bpj.2024.09.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/03/2024] [Accepted: 09/26/2024] [Indexed: 10/07/2024] Open
Abstract
We present the first-ever, fully discrete, stochastic model of triggered cardiac Ca2+ dynamics. Using anatomically accurate subcellular cardiac myocyte geometries, we simulate the molecular players involved in Ca2+ handling using high-resolution stochastic and explicit-particle methods at the level of an individual cardiac dyadic junction. Integrating data from multiple experimental sources, the model not only replicates the findings of traditional in silico studies and complements in vitro experimental data but also reveals new insights into the molecular mechanisms driving cardiac dysfunction under stress and disease conditions. We improve upon older, nondiscrete models using the same realistic geometry by incorporating molecular mechanisms for spontaneous, as well as triggered calcium-induced calcium release (CICR). Action potentials are used to activate L-type calcium channels (LTCC), triggering CICR through ryanodine receptors (RyRs) on the surface of the sarcoplasmic reticulum. These improvements allow for the specific focus on the couplon: the structure-function relationship between LTCC and RyR. We investigate the electrophysical effects of normal and diseased action potentials on CICR and interrogate the effects of dyadic junction deformation through detubulation and orphaning of RyR. Our work demonstrates the importance of the electrophysical integrity of the calcium release unit on CICR fidelity, giving insights into the molecular basis of heart disease. Finally, we provide a unique, detailed, molecular view of the CICR process using advanced rendering techniques. This easy-to-use model comes complete with tutorials and the necessary software for use and analysis to maximize usability and reproducibility. Our work focuses on quantifying, qualifying, and visualizing the behavior of the molecular species that underlie the function and dysfunction of subcellular cardiomyocyte systems.
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Affiliation(s)
- Sophia P Hirakis
- Computational Neurobiology Lab, The Salk Institute of Biological Studies, La Jolla, California; Department of Chemistry and Biochemistry, The University of California San Diego, La Jolla, California
| | - Thomas M Bartol
- Computational Neurobiology Lab, The Salk Institute of Biological Studies, La Jolla, California
| | - Ludovic Autin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California
| | - Rommie E Amaro
- Department of Chemistry and Biochemistry, The University of California San Diego, La Jolla, California.
| | - Terrence J Sejnowski
- Computational Neurobiology Lab, The Salk Institute of Biological Studies, La Jolla, California; Department of Chemistry and Biochemistry, The University of California San Diego, La Jolla, California.
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5
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Nguyen HTD, Perone G, Klena N, Vazzana R, Kaluthantrige Don F, Silva M, Sorrentino S, Swuec P, Leroux F, Kalebic N, Coscia F, Erdmann PS. Serialized on-grid lift-in sectioning for tomography (SOLIST) enables a biopsy at the nanoscale. Nat Methods 2024; 21:1693-1701. [PMID: 39271806 PMCID: PMC11399088 DOI: 10.1038/s41592-024-02384-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/17/2024] [Indexed: 09/15/2024]
Abstract
Cryo-focused ion beam milling has substantially advanced our understanding of molecular processes by opening windows into cells. However, applying this technique to complex samples, such as tissues, has presented considerable technical challenges. Here we introduce an innovative adaptation of the cryo-lift-out technique, serialized on-grid lift-in sectioning for tomography (SOLIST), addressing these limitations. SOLIST enhances throughput, minimizes ice contamination and improves sample stability for cryo-electron tomography. It thereby facilitates the high-resolution imaging of a wide range of specimens. We illustrate these advantages on reconstituted liquid-liquid phase-separated droplets, brain organoids and native tissues from the mouse brain, liver and heart. With SOLIST, cellular processes can now be investigated at molecular resolution directly in native tissue. Furthermore, our method has a throughput high enough to render cryo-lift-out a competitive tool for structural biology. This opens new avenues for unprecedented insights into cellular function and structure in health and disease, a 'biopsy at the nanoscale'.
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6
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Galaz-Montoya JG. The advent of preventive high-resolution structural histopathology by artificial-intelligence-powered cryogenic electron tomography. Front Mol Biosci 2024; 11:1390858. [PMID: 38868297 PMCID: PMC11167099 DOI: 10.3389/fmolb.2024.1390858] [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: 02/24/2024] [Accepted: 05/08/2024] [Indexed: 06/14/2024] Open
Abstract
Advances in cryogenic electron microscopy (cryoEM) single particle analysis have revolutionized structural biology by facilitating the in vitro determination of atomic- and near-atomic-resolution structures for fully hydrated macromolecular complexes exhibiting compositional and conformational heterogeneity across a wide range of sizes. Cryogenic electron tomography (cryoET) and subtomogram averaging are rapidly progressing toward delivering similar insights for macromolecular complexes in situ, without requiring tags or harsh biochemical purification. Furthermore, cryoET enables the visualization of cellular and tissue phenotypes directly at molecular, nanometric resolution without chemical fixation or staining artifacts. This forward-looking review covers recent developments in cryoEM/ET and related technologies such as cryogenic focused ion beam milling scanning electron microscopy and correlative light microscopy, increasingly enhanced and supported by artificial intelligence algorithms. Their potential application to emerging concepts is discussed, primarily the prospect of complementing medical histopathology analysis. Machine learning solutions are poised to address current challenges posed by "big data" in cryoET of tissues, cells, and macromolecules, offering the promise of enabling novel, quantitative insights into disease processes, which may translate into the clinic and lead to improved diagnostics and targeted therapeutics.
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Affiliation(s)
- Jesús G. Galaz-Montoya
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, United States
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7
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Fry MY, Navarro PP, Hakim P, Ananda VY, Qin X, Landoni JC, Rath S, Inde Z, Lugo CM, Luce BE, Ge Y, McDonald JL, Ali I, Ha LL, Kleinstiver BP, Chan DC, Sarosiek KA, Chao LH. In situ architecture of Opa1-dependent mitochondrial cristae remodeling. EMBO J 2024; 43:391-413. [PMID: 38225406 PMCID: PMC10897290 DOI: 10.1038/s44318-024-00027-2] [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: 01/14/2023] [Revised: 12/15/2023] [Accepted: 12/22/2023] [Indexed: 01/17/2024] Open
Abstract
Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria, while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and show a compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling.
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Affiliation(s)
- Michelle Y Fry
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Paula P Navarro
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Pusparanee Hakim
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Virly Y Ananda
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Xingping Qin
- John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Molecular and Integrative Physiological Sciences (MIPS) Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Lab of Systems Pharmacology, Harvard Program in Therapeutic Science, Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Juan C Landoni
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Sneha Rath
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Zintis Inde
- John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Molecular and Integrative Physiological Sciences (MIPS) Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Lab of Systems Pharmacology, Harvard Program in Therapeutic Science, Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | | | - Bridget E Luce
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Yifan Ge
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Interdisciplinary Research Center of Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai, China
| | - Julie L McDonald
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ilzat Ali
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Leillani L Ha
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA
| | - Benjamin P Kleinstiver
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA
- Department of Pathology, Harvard Medical School, Boston, MA, USA
| | - David C Chan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Kristopher A Sarosiek
- John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Molecular and Integrative Physiological Sciences (MIPS) Program, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Lab of Systems Pharmacology, Harvard Program in Therapeutic Science, Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Luke H Chao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
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8
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Mageswaran SK, Grotjahn DA, Zeng X, Barad BA, Medina M, Hoang MH, Dobro MJ, Chang YW, Xu M, Yang WY, Jensen GJ. Nanoscale details of mitochondrial constriction revealed by cryoelectron tomography. Biophys J 2023; 122:3768-3782. [PMID: 37533259 PMCID: PMC10541493 DOI: 10.1016/j.bpj.2023.07.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 07/14/2023] [Accepted: 07/31/2023] [Indexed: 08/04/2023] Open
Abstract
Mitochondria adapt to changing cellular environments, stress stimuli, and metabolic demands through dramatic morphological remodeling of their shape, and thus function. Such mitochondrial dynamics is often dependent on cytoskeletal filament interactions. However, the precise organization of these filamentous assemblies remains speculative. Here, we apply cryogenic electron tomography to directly image the nanoscale architecture of the cytoskeletal-membrane interactions involved in mitochondrial dynamics in response to damage. We induced mitochondrial damage via membrane depolarization, a cellular stress associated with mitochondrial fragmentation and mitophagy. We find that, in response to acute membrane depolarization, mammalian mitochondria predominantly organize into tubular morphology that abundantly displays constrictions. We observe long bundles of both unbranched actin and septin filaments enriched at these constrictions. We also observed septin-microtubule interactions at these sites and elsewhere, suggesting that these two filaments guide each other in the cytosolic space. Together, our results provide empirical parameters for the architecture of mitochondrial constriction factors to validate/refine existing models and inform the development of new ones.
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Affiliation(s)
- Shrawan Kumar Mageswaran
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California; Department of Biophysics and Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Danielle Ann Grotjahn
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California.
| | - Xiangrui Zeng
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Benjamin Asher Barad
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California
| | - Michaela Medina
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California
| | - My Hanh Hoang
- Department of Biophysics and Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Yi-Wei Chang
- Department of Biophysics and Biochemistry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Min Xu
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Wei Yuan Yang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Grant J Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California; Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah.
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9
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Beinsteiner B, Billas IML, Moras D. Structural insights into the HNF4 biology. Front Endocrinol (Lausanne) 2023; 14:1197063. [PMID: 37404310 PMCID: PMC10315846 DOI: 10.3389/fendo.2023.1197063] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 06/01/2023] [Indexed: 07/06/2023] Open
Abstract
Hepatocyte Nuclear Factor 4 (HNF4) is a transcription factor (TF) belonging to the nuclear receptor (NR) family that is expressed in liver, kidney, intestine and pancreas. It is a master regulator of liver-specific gene expression, in particular those genes involved in lipid transport and glucose metabolism and is crucial for the cellular differentiation during development. Dysregulation of HNF4 is linked to human diseases, such as type I diabetes (MODY1) and hemophilia. Here, we review the structures of the isolated HNF4 DNA binding domain (DBD) and ligand binding domain (LBD) and that of the multidomain receptor and compare them with the structures of other NRs. We will further discuss the biology of the HNF4α receptors from a structural perspective, in particular the effect of pathological mutations and of functionally critical post-translational modifications on the structure-function of the receptor.
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Affiliation(s)
- Brice Beinsteiner
- Laboratory IGBMC (Institute of Genetics and of Molecular and Cellular Biology), Centre for Integrative Biology (CBI), Illkirch, France
- Université de Strasbourg (Unistra), Strasbourg, France
- Institut National de la Santé et de la Recherche Médicale (INSERM) U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France
| | - Isabelle M. L. Billas
- Laboratory IGBMC (Institute of Genetics and of Molecular and Cellular Biology), Centre for Integrative Biology (CBI), Illkirch, France
- Université de Strasbourg (Unistra), Strasbourg, France
- Institut National de la Santé et de la Recherche Médicale (INSERM) U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France
| | - Dino Moras
- Laboratory IGBMC (Institute of Genetics and of Molecular and Cellular Biology), Centre for Integrative Biology (CBI), Illkirch, France
- Université de Strasbourg (Unistra), Strasbourg, France
- Institut National de la Santé et de la Recherche Médicale (INSERM) U1258, Illkirch, France
- Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France
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10
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Kim HHS, Uddin MR, Xu M, Chang YW. Computational Methods Toward Unbiased Pattern Mining and Structure Determination in Cryo-Electron Tomography Data. J Mol Biol 2023; 435:168068. [PMID: 37003470 PMCID: PMC10164694 DOI: 10.1016/j.jmb.2023.168068] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/19/2023] [Accepted: 03/26/2023] [Indexed: 04/03/2023]
Abstract
Cryo-electron tomography can uniquely probe the native cellular environment for macromolecular structures. Tomograms feature complex data with densities of diverse, densely crowded macromolecular complexes, low signal-to-noise, and artifacts such as the missing wedge effect. Post-processing of this data generally involves isolating regions or particles of interest from tomograms, organizing them into related groups, and rendering final structures through subtomogram averaging. Template-matching and reference-based structure determination are popular analysis methods but are vulnerable to biases and can often require significant user input. Most importantly, these approaches cannot identify novel complexes that reside within the imaged cellular environment. To reliably extract and resolve structures of interest, efficient and unbiased approaches are therefore of great value. This review highlights notable computational software and discusses how they contribute to making automated structural pattern discovery a possibility. Perspectives emphasizing the importance of features for user-friendliness and accessibility are also presented.
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Affiliation(s)
- Hannah Hyun-Sook Kim
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. https://twitter.com/hannahinthelab
| | - Mostofa Rafid Uddin
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA. https://twitter.com/duran_rafid
| | - Min Xu
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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11
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Navarro PP, Vettiger A, Ananda VY, Llopis PM, Allolio C, Bernhardt TG, Chao LH. Cell wall synthesis and remodelling dynamics determine division site architecture and cell shape in Escherichia coli. Nat Microbiol 2022; 7:1621-1634. [PMID: 36097171 PMCID: PMC9519445 DOI: 10.1038/s41564-022-01210-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 07/21/2022] [Indexed: 01/19/2023]
Abstract
The bacterial division apparatus catalyses the synthesis and remodelling of septal peptidoglycan (sPG) to build the cell wall layer that fortifies the daughter cell poles. Understanding of this essential process has been limited by the lack of native three-dimensional views of developing septa. Here, we apply state-of-the-art cryogenic electron tomography (cryo-ET) and fluorescence microscopy to visualize the division site architecture and sPG biogenesis dynamics of the Gram-negative bacterium Escherichia coli. We identify a wedge-like sPG structure that fortifies the ingrowing septum. Experiments with strains defective in sPG biogenesis revealed that the septal architecture and mode of division can be modified to more closely resemble that of other Gram-negative (Caulobacter crescentus) or Gram-positive (Staphylococcus aureus) bacteria, suggesting that a conserved mechanism underlies the formation of different septal morphologies. Finally, analysis of mutants impaired in amidase activation (ΔenvC ΔnlpD) showed that cell wall remodelling affects the placement and stability of the cytokinetic ring. Taken together, our results support a model in which competition between the cell elongation and division machineries determines the shape of cell constrictions and the poles they form. They also highlight how the activity of the division system can be modulated to help generate the diverse array of shapes observed in the bacterial domain.
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Affiliation(s)
- Paula P Navarro
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Andrea Vettiger
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Virly Y Ananda
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | | | - Christoph Allolio
- Faculty of Mathematics and Physics, Mathematical Institute, Charles University, Prague, Czech Republic
| | - Thomas G Bernhardt
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA.
| | - Luke H Chao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
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