1
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Barchet C, Fréchin L, Holvec S, Hazemann I, von Loeffelholz O, Klaholz BP. Focused classifications and refinements in high-resolution single particle cryo-EM analysis. J Struct Biol 2023; 215:108015. [PMID: 37659578 DOI: 10.1016/j.jsb.2023.108015] [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: 07/22/2022] [Revised: 06/27/2023] [Accepted: 08/17/2023] [Indexed: 09/04/2023]
Abstract
Recent advances in cryo electron microscopy (cryo-EM) and image processing provide new opportunities to analyse drug targets at high resolution. However, structural heterogeneity limits resolution in many practical cases, hence restricting the level at which structural details can be analysed and drug design be performed. As structural disorder is not spread throughout the entire structure of a given macromolecular complex but instead is found in certain regions that move with respect to others and covering molecular scales from domain conformational changes up to the level of side chain conformations in ligand binding pockets, it is possible to focus the attention on those regions and the associated relative movements. Here we show how the usage of focused classifications and refinements provide insights into global conformational arrangements, exemplified on the human ribosome and on the cannabinoid G protein coupled receptor (GPCR), and how they can improve the local map resolution from an essentially disordered region to the 3-4 Å and finally to the 2 Å resolution range. A systematic analysis with variable spherical masks during focused refinement is presented showing that the choice of an optimal mask size helps refining to high resolution. This study covers several practical approaches on 4 examples illustrating how important mask size & shape and including neighbouring structural elements are for a focused analysis of a macromolecular complex. Such methods will be crucial for cryo-EM structure-based drug design of various medical targets and are applicable to single particle cryo-EM and electron tomography data.
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Affiliation(s)
- Charles Barchet
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Léo Fréchin
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Samuel Holvec
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Isabelle Hazemann
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Ottilie von Loeffelholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Bruno P Klaholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France.
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2
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Langeberg CJ, Kieft JS. A generalizable scaffold-based approach for structure determination of RNAs by cryo-EM. Nucleic Acids Res 2023; 51:e100. [PMID: 37791881 PMCID: PMC10639074 DOI: 10.1093/nar/gkad784] [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: 03/20/2023] [Revised: 08/31/2023] [Accepted: 09/24/2023] [Indexed: 10/05/2023] Open
Abstract
Single-particle cryo-electron microscopy (cryo-EM) can reveal the structures of large and often dynamic molecules, but smaller biomolecules (≤50 kDa) remain challenging targets due to their intrinsic low signal to noise ratio. Methods to help resolve small proteins have been applied but development of similar approaches to aid in structural determination of small, structured RNA elements have lagged. Here, we present a scaffold-based approach that we used to recover maps of sub-25 kDa RNA domains to 4.5-5.0 Å. While lacking the detail of true high-resolution maps, these maps are suitable for model building and preliminary structure determination. We demonstrate this method helped faithfully recover the structure of several RNA elements of known structure, and that it promises to be generalized to other RNAs without disturbing their native fold. This approach may streamline the sample preparation process and reduce the optimization required for data collection. This first-generation scaffold approach provides a robust system to aid in RNA structure determination by cryo-EM and lays the groundwork for further scaffold optimization to achieve higher resolution.
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Affiliation(s)
- Conner J Langeberg
- Department of Biochemistry and Molecular Genetics, Aurora, CO 80045, USA
| | - Jeffrey S Kieft
- Department of Biochemistry and Molecular Genetics, Aurora, CO 80045, USA
- RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
- New York Structural Biology Center, New York, NY 10027, USA
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3
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Langeberg CJ, Kieft JS. A Generalizable Scaffold-Based Approach for Structure Determination of RNAs by Cryo-EM. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.06.547879. [PMID: 37461535 PMCID: PMC10350027 DOI: 10.1101/2023.07.06.547879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Single-particle cryo-electron microscopy (cryo-EM) can reveal the structures of large and often dynamic molecules, but smaller biomolecules remain challenging targets due to their intrinsic low signal to noise ratio. Methods to resolve small proteins have been applied but development of similar approaches for small structured RNA elements have lagged. Here, we present a scaffold-based approach that we used to recover maps of sub-25 kDa RNA domains to 4.5 - 5.0 Å. While lacking the detail of true high-resolution maps, these are suitable for model building and preliminary structure determination. We demonstrate this method faithfully recovers the structure of several RNA elements of known structure, and it promises to be generalized to other RNAs without disturbing their native fold. This approach may streamline the sample preparation process and reduce the optimization required for data collection. This first-generation scaffold approach provides a system for RNA structure determination by cryo-EM and lays the groundwork for further scaffold optimization to achieve higher resolution.
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4
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Wang X, Lu Y, Lin X, Li J, Zhang Z. An Unsupervised Classification Algorithm for Heterogeneous Cryo-EM Projection Images Based on Autoencoders. Int J Mol Sci 2023; 24:ijms24098380. [PMID: 37176089 PMCID: PMC10179202 DOI: 10.3390/ijms24098380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/29/2023] [Accepted: 04/30/2023] [Indexed: 05/15/2023] Open
Abstract
Heterogeneous three-dimensional (3D) reconstruction in single-particle cryo-electron microscopy (cryo-EM) is an important but very challenging technique for recovering the conformational heterogeneity of flexible biological macromolecules such as proteins in different functional states. Heterogeneous projection image classification is a feasible solution to solve the structural heterogeneity problem in single-particle cryo-EM. The majority of heterogeneous projection image classification methods are developed using supervised learning technology or require a large amount of a priori knowledge, such as the orientations or common lines of the projection images, which leads to certain limitations in their practical applications. In this paper, an unsupervised heterogeneous cryo-EM projection image classification algorithm based on autoencoders is proposed, which only needs to know the number of heterogeneous 3D structures in the dataset and does not require any labeling information of the projection images or other a priori knowledge. A simple autoencoder with multi-layer perceptrons trained in iterative mode and a complex autoencoder with residual networks trained in one-pass learning mode are implemented to convert heterogeneous projection images into latent variables. The extracted high-dimensional features are reduced to two dimensions using the uniform manifold approximation and projection dimensionality reduction algorithm, and then clustered using the spectral clustering algorithm. The proposed algorithm is applied to two heterogeneous cryo-EM datasets for heterogeneous 3D reconstruction. Experimental results show that the proposed algorithm can effectively extract category features of heterogeneous projection images and achieve high classification and reconstruction accuracy, indicating that the proposed algorithm is effective for heterogeneous 3D reconstruction in single-particle cryo-EM.
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Affiliation(s)
- Xiangwen Wang
- College of Computer Science and Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Yonggang Lu
- School of Information Science and Engineering, Lanzhou University, Lanzhou 730000, China
| | - Xianghong Lin
- College of Computer Science and Engineering, Northwest Normal University, Lanzhou 730070, China
| | - Jianwei Li
- School of Information Science and Engineering, Lanzhou University, Lanzhou 730000, China
| | - Zequn Zhang
- College of Computer Science and Engineering, Northwest Normal University, Lanzhou 730070, China
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5
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Halling DB, Philpo AE, Aldrich RW. Calcium dependence of both lobes of calmodulin is involved in binding to a cytoplasmic domain of SK channels. eLife 2022; 11:e81303. [PMID: 36583726 PMCID: PMC9803350 DOI: 10.7554/elife.81303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 12/15/2022] [Indexed: 12/31/2022] Open
Abstract
KCa2.1-3 Ca2+-activated K+-channels (SK) require calmodulin to gate in response to cellular Ca2+. A model for SK gating proposes that the N-terminal domain (N-lobe) of calmodulin is required for activation, but an immobile C-terminal domain (C-lobe) has constitutive, Ca2+-independent binding. Although structures support a domain-driven hypothesis of SK gate activation by calmodulin, only a partial understanding is possible without measuring both channel activity and protein binding. We measured SK2 (KCa2.2) activity using inside-out patch recordings. Currents from calmodulin-disrupted SK2 channels can be restored with exogenously applied calmodulin. We find that SK2 activity only approaches full activation with full-length calmodulin with both an N- and a C-lobe. We measured calmodulin binding to a C-terminal SK peptide (SKp) using both composition-gradient multi-angle light-scattering and tryptophan emission spectra. Isolated lobes bind to SKp with high affinity, but isolated lobes do not rescue SK2 activity. Consistent with earlier models, N-lobe binding to SKp is stronger in Ca2+, and C-lobe-binding affinity is strong independent of Ca2+. However, a native tryptophan in SKp is sensitive to Ca2+ binding to both the N- and C-lobes of calmodulin at Ca2+ concentrations that activate SK2, demonstrating that the C-lobe interaction with SKp changes with Ca2+. Our peptide-binding data and electrophysiology show that SK gating models need deeper scrutiny. We suggest that the Ca2+-dependent associations of both lobes of calmodulin to SKp are crucial events during gating. Additional investigations are necessary to complete a mechanistic gating model consistent with binding, physiology, and structure.
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Affiliation(s)
- David B Halling
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
| | - Ashley E Philpo
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
| | - Richard W Aldrich
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
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6
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Abstract
In recent years, protein structure analysis using cryo-electron microscopy(cryo-EM) has expanded and improved. In this review, we discuss many recent improvements to the field, the problems those improvements hope to solve, and some of the still unanswered questions. Most notably, this review will discuss improvements in resolving small or fragmented protein structures, as well as methods to improve the signal-to-noise ratio of the data by increasing image contrast using carbon-based systems. We will also describe how, in the last 5 years, methodological improvements have allowed for better 3D image resolution by capturing a continuum of 3D images. We will provide examples of these methods in practice and discuss how these improved methods may be used in small-molecule drug discovery and development. © 2022 Wiley Periodicals LLC.
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Affiliation(s)
- Angela Cabral
- Department of Molecular Biology and Biochemistry, University of California Irvine, Steinhaus Hall, Irvine, CA 92694-3900, USA
| | - Julia Elise Cabral
- Department of Molecular Biology and Biochemistry, University of California Irvine, Steinhaus Hall, Irvine, CA 92694-3900, USA
| | - Reginald McNulty
- Department of Molecular Biology and Biochemistry, University of California Irvine, Steinhaus Hall, Irvine, CA 92694-3900, USA
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7
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Harrison JJEK, Passos DO, Bruhn JF, Bauman JD, Tuberty L, DeStefano JJ, Ruiz FX, Lyumkis D, Arnold E. Cryo-EM structure of the HIV-1 Pol polyprotein provides insights into virion maturation. SCIENCE ADVANCES 2022; 8:eabn9874. [PMID: 35857464 PMCID: PMC9258950 DOI: 10.1126/sciadv.abn9874] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 05/20/2022] [Indexed: 06/15/2023]
Abstract
Key proteins of retroviruses and other RNA viruses are translated and subsequently processed from polyprotein precursors by the viral protease (PR). Processing of the HIV Gag-Pol polyprotein yields the HIV structural proteins and enzymes. Structures of the mature enzymes PR, reverse transcriptase (RT), and integrase (IN) aided understanding of catalysis and design of antiretrovirals, but knowledge of the Pol precursor architecture and function before PR cleavage is limited. We developed a system to produce stable HIV-1 Pol and determined its cryo-electron microscopy structure. RT in Pol has a similar arrangement to the mature RT heterodimer, and its dimerization may draw together two PR monomers to activate proteolytic processing. HIV-1 thus may leverage the dimerization interfaces in Pol to regulate assembly and maturation of polyprotein precursors.
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Affiliation(s)
- Jerry Joe E. K. Harrison
- Center for Advanced Biotechnology and Medicine (CABM), Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
- Department of Chemistry, University of Ghana, Legon, Ghana
| | | | - Jessica F. Bruhn
- The Salk Institute for Biological Studies, La Jolla, CA, USA
- NanoImaging Services, San Diego, CA, USA
| | - Joseph D. Bauman
- Center for Advanced Biotechnology and Medicine (CABM), Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
| | - Lynda Tuberty
- Center for Advanced Biotechnology and Medicine (CABM), Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
| | - Jeffrey J. DeStefano
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
- Maryland Pathogen Research Institute, University of Maryland, College Park, MD, USA
| | - Francesc Xavier Ruiz
- Center for Advanced Biotechnology and Medicine (CABM), Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
| | - Dmitry Lyumkis
- The Salk Institute for Biological Studies, La Jolla, CA, USA
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Eddy Arnold
- Center for Advanced Biotechnology and Medicine (CABM), Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
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8
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Vilas JL, Carazo JM, Sorzano COS. Emerging Themes in CryoEM─Single Particle Analysis Image Processing. Chem Rev 2022; 122:13915-13951. [PMID: 35785962 PMCID: PMC9479088 DOI: 10.1021/acs.chemrev.1c00850] [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] [Indexed: 11/29/2022]
Abstract
Cryo-electron microscopy (CryoEM) has become a vital technique in structural biology. It is an interdisciplinary field that takes advantage of advances in biochemistry, physics, and image processing, among other disciplines. Innovations in these three basic pillars have contributed to the boosting of CryoEM in the past decade. This work reviews the main contributions in image processing to the current reconstruction workflow of single particle analysis (SPA) by CryoEM. Our review emphasizes the time evolution of the algorithms across the different steps of the workflow differentiating between two groups of approaches: analytical methods and deep learning algorithms. We present an analysis of the current state of the art. Finally, we discuss the emerging problems and challenges still to be addressed in the evolution of CryoEM image processing methods in SPA.
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Affiliation(s)
- Jose Luis Vilas
- Biocomputing Unit, Centro Nacional de Biotecnologia (CNB-CSIC), Darwin, 3, Campus Universidad Autonoma, 28049 Cantoblanco, Madrid, Spain
| | - Jose Maria Carazo
- Biocomputing Unit, Centro Nacional de Biotecnologia (CNB-CSIC), Darwin, 3, Campus Universidad Autonoma, 28049 Cantoblanco, Madrid, Spain
| | - Carlos Oscar S Sorzano
- Biocomputing Unit, Centro Nacional de Biotecnologia (CNB-CSIC), Darwin, 3, Campus Universidad Autonoma, 28049 Cantoblanco, Madrid, Spain
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9
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Continuum dynamics and statistical correction of compositional heterogeneity in multivalent IDP oligomers resolved by single-particle EM. J Mol Biol 2022; 434:167520. [PMID: 35245498 PMCID: PMC9050902 DOI: 10.1016/j.jmb.2022.167520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 01/17/2022] [Accepted: 02/27/2022] [Indexed: 12/29/2022]
Abstract
Multivalent intrinsically disordered protein (IDP) complexes are prevalent in biology and act in regulation of diverse processes, including transcription, signaling events, and the assembly and disassembly of complex macromolecular architectures. These systems pose significant challenges to structural investigation, due to continuum dynamics imparted by the IDP and compositional heterogeneity resulting from characteristic low-affinity interactions. Here, we developed a modular pipeline for automated single-particle electron microscopy (EM) distribution analysis of common but relatively understudied semi-ordered systems: 'beads-on-a-string' assemblies, composed of IDPs bound at multivalent sites to the ubiquitous ∼20 kDa cross-linking hub protein LC8. This approach quantifies conformational geometries and compositional heterogeneity on a single-particle basis, and statistically corrects spurious observations arising from random proximity of bound and unbound LC8. The statistical correction is generically applicable to oligomer characterization and not specific to our pipeline. Following validation, the approach was applied to the nuclear pore IDP Nup159 and the transcription factor ASCIZ. This analysis unveiled significant compositional and conformational diversity in both systems that could not be obtained from ensemble single particle EM class-averaging strategies, and new insights for exploring how these architectural properties might contribute to their physiological roles in supramolecular assembly and transcriptional regulation. We expect that this approach may be adopted to many other intrinsically disordered systems that have evaded traditional methods of structural characterization.
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10
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Abstract
Three-dimensional protein structural data at the molecular level are pivotal for successful precision medicine. Such data are crucial not only for discovering drugs that act to block the active site of the target mutant protein but also for clarifying to the patient and the clinician how the mutations harbored by the patient work. The relative paucity of structural data reflects their cost, challenges in their interpretation, and lack of clinical guidelines for their utilization. Rapid technological advancements in experimental high-resolution structural determination increasingly generate structures. Computationally, modeling algorithms, including molecular dynamics simulations, are becoming more powerful, as are compute-intensive hardware, particularly graphics processing units, overlapping with the inception of the exascale era. Accessible, freely available, and detailed structural and dynamical data can be merged with big data to powerfully transform personalized pharmacology. Here we review protein and emerging genome high-resolution data, along with means, applications, and examples underscoring their usefulness in precision medicine. Expected final online publication date for the Annual Review of Biomedical Data Science, Volume 5 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Ruth Nussinov
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, National Cancer Institute, Frederick, Maryland, USA; .,Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Hyunbum Jang
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, National Cancer Institute, Frederick, Maryland, USA;
| | - Guy Nir
- Department of Biochemistry and Molecular Biology, Department of Neuroscience, Cell Biology and Anatomy, and Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas, USA
| | - Chung-Jung Tsai
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer Immunometabolism, National Cancer Institute, Frederick, Maryland, USA;
| | - Feixiong Cheng
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.,Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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11
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Wang X, Lu Y, Lin X. Heterogeneous cryo-EM projection image classification using a two-stage spectral clustering based on novel distance measures. Brief Bioinform 2022; 23:6543485. [PMID: 35255494 DOI: 10.1093/bib/bbac032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/17/2022] [Accepted: 01/23/2022] [Indexed: 11/13/2022] Open
Abstract
Single-particle cryo-electron microscopy (cryo-EM) has become one of the mainstream technologies in the field of structural biology to determine the three-dimensional (3D) structures of biological macromolecules. Heterogeneous cryo-EM projection image classification is an effective way to discover conformational heterogeneity of biological macromolecules in different functional states. However, due to the low signal-to-noise ratio of the projection images, the classification of heterogeneous cryo-EM projection images is a very challenging task. In this paper, two novel distance measures between projection images integrating the reliability of common lines, pixel intensity and class averages are designed, and then a two-stage spectral clustering algorithm based on the two distance measures is proposed for heterogeneous cryo-EM projection image classification. In the first stage, the novel distance measure integrating common lines and pixel intensities of projection images is used to obtain preliminary classification results through spectral clustering. In the second stage, another novel distance measure integrating the first novel distance measure and class averages generated from each group of projection images is used to obtain the final classification results through spectral clustering. The proposed two-stage spectral clustering algorithm is applied on a simulated and a real cryo-EM dataset for heterogeneous reconstruction. Results show that the two novel distance measures can be used to improve the classification performance of spectral clustering, and using the proposed two-stage spectral clustering algorithm can achieve higher classification and reconstruction accuracy than using RELION and XMIPP.
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Affiliation(s)
- Xiangwen Wang
- School of Information Science and Engineering, Lanzhou University, 730000, Lanzhou, China.,College of Computer Science and Engineering, Northwest Normal University, 730070, Lanzhou, China
| | - Yonggang Lu
- School of Information Science and Engineering, Lanzhou University, 730000, Lanzhou, China
| | - Xianghong Lin
- College of Computer Science and Engineering, Northwest Normal University, 730070, Lanzhou, China
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12
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Beckers M, Mann D, Sachse C. Structural interpretation of cryo-EM image reconstructions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 160:26-36. [PMID: 32735944 DOI: 10.1016/j.pbiomolbio.2020.07.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/03/2020] [Accepted: 07/13/2020] [Indexed: 06/11/2023]
Abstract
The productivity of single-particle cryo-EM as a structure determination method has rapidly increased as many novel biological structures are being elucidated. The ultimate result of the cryo-EM experiment is an atomic model that should faithfully represent the computed image reconstruction. Although the principal approach of atomic model building and refinement from maps resembles that of the X-ray crystallographic methods, there are important differences due to the unique properties resulting from the 3D image reconstructions. In this review, we discuss the practiced work-flow from the cryo-EM image reconstruction to the atomic model. We give an overview of (i) resolution determination methods in cryo-EM including local and directional resolution variation, (ii) cryo-EM map contrast optimization including complementary map types that can help in identifying ambiguous density features, (iii) atomic model building and (iv) refinement in various resolution regimes including (v) their validation and (vi) discuss differences between X-ray and cryo-EM maps. Based on the methods originally developed for X-ray crystallography, the path from 3D image reconstruction to atomic coordinates has become an integral and important part of the cryo-EM structure determination work-flow that routinely delivers atomic models.
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Affiliation(s)
- Maximilian Beckers
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstraße 1, 69117, Heidelberg, Germany; Candidate for Joint PhD Degree from EMBL and Heidelberg University, Faculty of Biosciences, Germany; Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons (ER-C-3/Structural Biology), Forschungszentrum Jülich, 52425, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52425, Jülich, Germany
| | - Daniel Mann
- Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons (ER-C-3/Structural Biology), Forschungszentrum Jülich, 52425, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52425, Jülich, Germany
| | - Carsten Sachse
- Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons (ER-C-3/Structural Biology), Forschungszentrum Jülich, 52425, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52425, Jülich, Germany; Chemistry Department, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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13
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Yu J, Zhu H, Lape R, Greiner T, Du J, Lü W, Sivilotti L, Gouaux E. Mechanism of gating and partial agonist action in the glycine receptor. Cell 2021; 184:957-968.e21. [PMID: 33567265 PMCID: PMC8115384 DOI: 10.1016/j.cell.2021.01.026] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/16/2020] [Accepted: 01/15/2021] [Indexed: 12/14/2022]
Abstract
Ligand-gated ion channels mediate signal transduction at chemical synapses and transition between resting, open, and desensitized states in response to neurotransmitter binding. Neurotransmitters that produce maximum open channel probabilities (Po) are full agonists, whereas those that yield lower than maximum Po are partial agonists. Cys-loop receptors are an important class of neurotransmitter receptors, yet a structure-based understanding of the mechanism of partial agonist action has proven elusive. Here, we study the glycine receptor with the full agonist glycine and the partial agonists taurine and γ-amino butyric acid (GABA). We use electrophysiology to show how partial agonists populate agonist-bound, closed channel states and cryo-EM reconstructions to illuminate the structures of intermediate, pre-open states, providing insights into previously unseen conformational states along the receptor reaction pathway. We further correlate agonist-induced conformational changes to Po across members of the receptor family, providing a hypothetical mechanism for partial and full agonist action at Cys-loop receptors.
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Affiliation(s)
- Jie Yu
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Hongtao Zhu
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Remigijus Lape
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK
| | - Timo Greiner
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK
| | - Juan Du
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Wei Lü
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Lucia Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK.
| | - Eric Gouaux
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Howard Hughes Medical Institute, Oregon Health & Science University, Portland, OR 97239, USA.
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14
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Abdelsattar AS, Mansour Y, Aboul-Ela F. The Perturbed Free-Energy Landscape: Linking Ligand Binding to Biomolecular Folding. Chembiochem 2021; 22:1499-1516. [PMID: 33351206 DOI: 10.1002/cbic.202000695] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 12/19/2020] [Indexed: 12/24/2022]
Abstract
The effects of ligand binding on biomolecular conformation are crucial in drug design, enzyme mechanisms, the regulation of gene expression, and other biological processes. Descriptive models such as "lock and key", "induced fit", and "conformation selection" are common ways to interpret such interactions. Another historical model, linked equilibria, proposes that the free-energy landscape (FEL) is perturbed by the addition of ligand binding energy for the bound population of biomolecules. This principle leads to a unified, quantitative theory of ligand-induced conformation change, building upon the FEL concept. We call the map of binding free energy over biomolecular conformational space the "binding affinity landscape" (BAL). The perturbed FEL predicts/explains ligand-induced conformational changes conforming to all common descriptive models. We review recent experimental and computational studies that exemplify the perturbed FEL, with emphasis on RNA. This way of understanding ligand-induced conformation dynamics motivates new experimental and theoretical approaches to ligand design, structural biology and systems biology.
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Affiliation(s)
- Abdallah S Abdelsattar
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
| | - Youssef Mansour
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
| | - Fareed Aboul-Ela
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
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15
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A set of common movements within GPCR-G-protein complexes from variability analysis of cryo-EM datasets. J Struct Biol 2021; 213:107699. [PMID: 33545352 DOI: 10.1016/j.jsb.2021.107699] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/05/2021] [Accepted: 01/22/2021] [Indexed: 12/11/2022]
Abstract
G-protein coupled receptors (GPCRs) are among the most versatile signal transducers in the cell. Once activated, GPCRs sample a large conformational space and couple to G-proteins to initiate distinct signaling pathways. The dynamical behavior of GPCR-G-protein complexes is difficult characterize structurally, and it might hinder obtaining routine high-resolution density maps in single-particle reconstructions. Here, we used variability analysis on the rhodopsin-Gi-Fab16 complex cryo-EM dataset, and the results provide insights into the dynamic nature of the receptor-complex interaction. We compare the outcome of this analysis with recent results obtained on the cannabinoid-Gi- and secretin-Gs-receptor complexes. Despite differences related to the biochemical compositions of the three samples, a set of consensus movements emerges. We anticipate that systematic variability analysis on GPCR-G-protein complexes may provide useful information not only at the biological level, but also for improving the preparation of more stable samples for cryo-EM single-particle analysis.
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16
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Protein Synthesis in the Developing Neocortex at Near-Atomic Resolution Reveals Ebp1-Mediated Neuronal Proteostasis at the 60S Tunnel Exit. Mol Cell 2020; 81:304-322.e16. [PMID: 33357414 DOI: 10.1016/j.molcel.2020.11.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 09/04/2020] [Accepted: 11/19/2020] [Indexed: 02/07/2023]
Abstract
Protein synthesis must be finely tuned in the developing nervous system as the final essential step of gene expression. This study investigates the architecture of ribosomes from the neocortex during neurogenesis, revealing Ebp1 as a high-occupancy 60S peptide tunnel exit (TE) factor during protein synthesis at near-atomic resolution by cryoelectron microscopy (cryo-EM). Ribosome profiling demonstrated Ebp1-60S binding is highest during start codon initiation and N-terminal peptide elongation, regulating ribosome occupancy of these codons. Membrane-targeting domains emerging from the 60S tunnel, which recruit SRP/Sec61 to the shared binding site, displace Ebp1. Ebp1 is particularly abundant in the early-born neural stem cell (NSC) lineage and regulates neuronal morphology. Ebp1 especially impacts the synthesis of membrane-targeted cell adhesion molecules (CAMs), measured by pulsed stable isotope labeling by amino acids in cell culture (pSILAC)/bioorthogonal noncanonical amino acid tagging (BONCAT) mass spectrometry (MS). Therefore, Ebp1 is a central component of protein synthesis, and the ribosome TE is a focal point of gene expression control in the molecular specification of neuronal morphology during development.
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17
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Aksel T, Yu Z, Cheng Y, Douglas SM. Molecular goniometers for single-particle cryo-electron microscopy of DNA-binding proteins. Nat Biotechnol 2020; 39:378-386. [PMID: 33077960 PMCID: PMC7956247 DOI: 10.1038/s41587-020-0716-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 09/21/2020] [Indexed: 12/21/2022]
Abstract
Correct reconstruction of macromolecular structure by cryo-electron microscopy (cryo-EM) relies on accurate determination of the orientation of single-particle images. For small (<100 kDa) DNA-binding proteins, obtaining particle images with sufficiently asymmetric features to correctly guide alignment is challenging. We apply DNA origami to construct molecular goniometers—instruments that precisely orient objects—and use them to dock a DNA-binding protein on a double-helix stage that has user-programmable tilt and rotation angles. We construct goniometers with fourteen different stage configurations to orient and visualize the protein just above the cryo-EM grid surface. Each goniometer has a distinct barcode pattern that we use during particle classification to assign angle priors to the bound protein. We use goniometers to obtain a 6.5 Å structure of BurrH, an 82-kDa DNA-binding protein whose helical pseudosymmetry prevents accurate image orientation using traditional cryo-EM. Our approach should be adaptable to other DNA-binding proteins as well as small proteins fused to DNA-binding domains. DNA origami orients single proteins on a surface to aid structure determination by cryo-electron microscopy.
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Affiliation(s)
- Tural Aksel
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA
| | - Zanlin Yu
- Howard Hughes Medical Institute and the Department of Biochemistry & Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Yifan Cheng
- Howard Hughes Medical Institute and the Department of Biochemistry & Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Shawn M Douglas
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA.
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18
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Nygaard R, Kim J, Mancia F. Cryo-electron microscopy analysis of small membrane proteins. Curr Opin Struct Biol 2020; 64:26-33. [PMID: 32603877 PMCID: PMC7665978 DOI: 10.1016/j.sbi.2020.05.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/05/2020] [Accepted: 05/19/2020] [Indexed: 12/31/2022]
Abstract
Recent advances in single-particle cryogenic-electron microscopy have facilitated an exponential growth in the number of membrane protein structures determined to close to atomic resolution. Nevertheless, despite improvements in microscope hardware, cryo-EM software and sample preparation techniques, challenges remain for structural analysis of small-sized membrane proteins (i.e.<150 kilodalton). Here we discuss recent examples of structures of macromolecules from this category determined by cryo-EM. We analyze the underlying difficulties, the enabling technologies such as the use of antibody fragments to gain size and provide fiducials for particle alignment, and the unresolved issues like dislocation of complexes at the air-water interface. Finally, we briefly highlight the biological relevance of some of these success stories, and our predictions for the future.
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Affiliation(s)
- Rie Nygaard
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jonathan Kim
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Filippo Mancia
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA.
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19
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Yoder N, Jalali-Yazdi F, Noreng S, Houser A, Baconguis I, Gouaux E. Light-coupled cryo-plunger for time-resolved cryo-EM. J Struct Biol 2020; 212:107624. [PMID: 32950604 DOI: 10.1016/j.jsb.2020.107624] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 09/08/2020] [Accepted: 09/11/2020] [Indexed: 12/26/2022]
Abstract
Proteins are dynamic molecules that can undergo rapid conformational rearrangements in response to stimuli. These structural changes are often critical to protein function, and thus elucidating time-dependent conformational landscapes has been a long-standing goal of structural biology. To harness the power of single particle cryo-EM methods to enable 'time-resolved' structure determination, we have developed a light-coupled cryo-plunger that pairs flash-photolysis of caged ligands with rapid sample vitrification. The 'flash-plunger' consists of a high-power ultraviolet LED coupled with focusing optics and a motorized linear actuator, enabling the user to immobilize protein targets in vitreous ice within a programmable time window - as short as tens of milliseconds - after stimulus delivery. The flash-plunger is a simple, inexpensive and flexible tool to explore short-lived conformational states previously unobtainable by conventional sample preparation methods.
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Affiliation(s)
- Nate Yoder
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Farzad Jalali-Yazdi
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Sigrid Noreng
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Alexandra Houser
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Isabelle Baconguis
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Eric Gouaux
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Howard Hughes Medical Institute, Oregon Health & Science University, Portland, OR 97239, USA.
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20
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Thompson MC, Yeates TO, Rodriguez JA. Advances in methods for atomic resolution macromolecular structure determination. F1000Res 2020; 9:F1000 Faculty Rev-667. [PMID: 32676184 PMCID: PMC7333361 DOI: 10.12688/f1000research.25097.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/25/2020] [Indexed: 12/13/2022] Open
Abstract
Recent technical advances have dramatically increased the power and scope of structural biology. New developments in high-resolution cryo-electron microscopy, serial X-ray crystallography, and electron diffraction have been especially transformative. Here we highlight some of the latest advances and current challenges at the frontiers of atomic resolution methods for elucidating the structures and dynamical properties of macromolecules and their complexes.
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Affiliation(s)
- Michael C. Thompson
- Department of Chemistry and Chemical Biology, University of California, Merced, CA, USA
| | - Todd O. Yeates
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, USA
- UCLA-DOE Institute for Genomics and Proteomics, Los Angeles, CA, USA
| | - Jose A. Rodriguez
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, USA
- UCLA-DOE Institute for Genomics and Proteomics, Los Angeles, CA, USA
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21
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Yeates TO, Agdanowski MP, Liu Y. Development of imaging scaffolds for cryo-electron microscopy. Curr Opin Struct Biol 2020; 60:142-149. [PMID: 32066085 DOI: 10.1016/j.sbi.2020.01.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 12/14/2022]
Abstract
Following recent hardware and software developments, single particle cryo-electron microscopy (cryo-EM) has become one of the most popular structural biology tools. Many targets, such as viruses, large protein complexes and oligomeric membrane proteins, have been resolved to atomic resolution using single-particle cryo-EM, which relies on the accurate assignment of particle location and orientation from intrinsically noisy projection images. The same image processing procedures are more challenging for smaller proteins due to their lower signal-to-noise ratios. Consequently, though most cellular proteins are less than 50kDa, so far it has been possible to solve cryo-EM structures near that size range for only a few favorable cases. Here we highlight some of the challenges and recent efforts to break through this lower size limit by engineering large scaffolds to rigidly display multiple small proteins for imaging. Future design efforts are noted.
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Affiliation(s)
- Todd O Yeates
- UCLA Department of Chemistry and Biochemistry, United States; UCLA-DOE Institute for Genomics and Proteomics, United States; UCLA Molecular Biology Institute, United States.
| | | | - Yuxi Liu
- UCLA Department of Chemistry and Biochemistry, United States; UCLA Molecular Biology Institute, United States
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22
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Tascón I, Sousa JS, Corey RA, Mills DJ, Griwatz D, Aumüller N, Mikusevic V, Stansfeld PJ, Vonck J, Hänelt I. Structural basis of proton-coupled potassium transport in the KUP family. Nat Commun 2020; 11:626. [PMID: 32005818 PMCID: PMC6994465 DOI: 10.1038/s41467-020-14441-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 01/10/2020] [Indexed: 12/05/2022] Open
Abstract
Potassium homeostasis is vital for all organisms, but is challenging in single-celled organisms like bacteria and yeast and immobile organisms like plants that constantly need to adapt to changing external conditions. KUP transporters facilitate potassium uptake by the co-transport of protons. Here, we uncover the molecular basis for transport in this widely distributed family. We identify the potassium importer KimA from Bacillus subtilis as a member of the KUP family, demonstrate that it functions as a K+/H+ symporter and report a 3.7 Å cryo-EM structure of the KimA homodimer in an inward-occluded, trans-inhibited conformation. By introducing point mutations, we identify key residues for potassium and proton binding, which are conserved among other KUP proteins. KUP transporters facilitate potassium uptake by the co-transport of protons and are key players in potassium homeostasis. Here authors identify the potassium importer KimA from Bacillus subtilis as a new member of the KUP transporter family and show the cryo-EM structure of KimA in an inward-occluded, trans-inhibited conformation.
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Affiliation(s)
- Igor Tascón
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Joana S Sousa
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Robin A Corey
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Deryck J Mills
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - David Griwatz
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Nadine Aumüller
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Vedrana Mikusevic
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, Oxford, UK.,School of Life Sciences & Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
| | - Inga Hänelt
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany.
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23
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Goodsell DS, Zardecki C, Di Costanzo L, Duarte JM, Hudson BP, Persikova I, Segura J, Shao C, Voigt M, Westbrook JD, Young JY, Burley SK. RCSB Protein Data Bank: Enabling biomedical research and drug discovery. Protein Sci 2019; 29:52-65. [PMID: 31531901 DOI: 10.1002/pro.3730] [Citation(s) in RCA: 184] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 12/11/2022]
Abstract
Analyses of publicly available structural data reveal interesting insights into the impact of the three-dimensional (3D) structures of protein targets important for discovery of new drugs (e.g., G-protein-coupled receptors, voltage-gated ion channels, ligand-gated ion channels, transporters, and E3 ubiquitin ligases). The Protein Data Bank (PDB) archive currently holds > 155,000 atomic-level 3D structures of biomolecules experimentally determined using crystallography, nuclear magnetic resonance spectroscopy, and electron microscopy. The PDB was established in 1971 as the first open-access, digital-data resource in biology, and is now managed by the Worldwide PDB partnership (wwPDB; wwPDB.org). US PDB operations are the responsibility of the Research Collaboratory for Structural Bioinformatics PDB (RCSB PDB). The RCSB PDB serves millions of RCSB.org users worldwide by delivering PDB data integrated with ∼40 external biodata resources, providing rich structural views of fundamental biology, biomedicine, and energy sciences. Recently published work showed that the PDB archival holdings facilitated discovery of ∼90% of the 210 new drugs approved by the US Food and Drug Administration 2010-2016. We review user-driven development of RCSB PDB services, examine growth of the PDB archive in terms of size and complexity, and present examples and opportunities for structure-guided drug discovery for challenging targets (e.g., integral membrane proteins).
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Affiliation(s)
- David S Goodsell
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,The Scripps Research Institute, La Jolla, California
| | - Christine Zardecki
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Luigi Di Costanzo
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Jose M Duarte
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer Center, University of California, San Diego, California
| | - Brian P Hudson
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Irina Persikova
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Joan Segura
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer Center, University of California, San Diego, California
| | - Chenghua Shao
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Maria Voigt
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - John D Westbrook
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Jasmine Y Young
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Stephen K Burley
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer Center, University of California, San Diego, California.,Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
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24
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Non-uniformity of projection distributions attenuates resolution in Cryo-EM. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 150:160-183. [PMID: 31525386 DOI: 10.1016/j.pbiomolbio.2019.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 09/02/2019] [Accepted: 09/07/2019] [Indexed: 11/23/2022]
Abstract
Virtually all single-particle cryo-EM experiments currently suffer from specimen adherence to the air-water interface, leading to a non-uniform distribution in the set of projection views. Whereas it is well accepted that uniform projection distributions can lead to high-resolution reconstructions, non-uniform (anisotropic) distributions can negatively affect map quality, elongate structural features, and in some cases, prohibit interpretation altogether. Although some consequences of non-uniform sampling have been described qualitatively, we know little about how sampling quantitatively affects resolution in cryo-EM. Here, we show how inhomogeneity in any projection distribution scheme attenuates the global Fourier Shell Correlation (FSC) in relation to the number of particles and a single geometrical parameter, which we term the sampling compensation factor (SCF). The reciprocal of the SCF is defined as the average over Fourier shells of the reciprocal of the per-particle sampling and normalized to unity for uniform distributions. The SCF therefore ranges from one to zero, with values close to the latter implying large regions of poorly sampled or completely missing data in Fourier space. Using two synthetic test cases, influenza hemagglutinin and human apoferritin, we demonstrate how any amount of sampling inhomogeneity always attenuates the FSC compared to a uniform distribution. We advocate quantitative evaluation of the SCF criterion to approximate the effect of non-uniform sampling on resolution within experimental single-particle cryo-EM reconstructions.
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25
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Fan X, Wang J, Zhang X, Yang Z, Zhang JC, Zhao L, Peng HL, Lei J, Wang HW. Single particle cryo-EM reconstruction of 52 kDa streptavidin at 3.2 Angstrom resolution. Nat Commun 2019; 10:2386. [PMID: 31160591 PMCID: PMC6546690 DOI: 10.1038/s41467-019-10368-w] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 05/06/2019] [Indexed: 11/09/2022] Open
Abstract
The fast development of single-particle cryogenic electron microscopy (cryo-EM) has made it more feasible to obtain the 3D structure of well-behaved macromolecules with a molecular weight higher than 300 kDa at ~3 Å resolution. However, it remains a challenge to obtain the high-resolution structures of molecules smaller than 200 kDa using single-particle cryo-EM. In this work, we apply the Cs-corrector-VPP-coupled cryo-EM to study the 52 kDa streptavidin (SA) protein supported on a thin layer of graphene and embedded in vitreous ice. We are able to solve both the apo-SA and biotin-bound SA structures at near-atomic resolution using single-particle cryo-EM. We demonstrate that the method has the potential to determine the structures of molecules as small as 39 kDa. It remains a challenge to obtain high-resolution structures of molecules smaller than 200 kDa using single particle cryo-EM. Here, the authors apply the Cs-corrector-VPP coupled cryo-EM and solve structures of the 52 kDa streptavidin (SA) protein at near-atomic resolution.
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Affiliation(s)
- Xiao Fan
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China.,Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xing Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Zi Yang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China.,Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jin-Can Zhang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Lingyun Zhao
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Hai-Lin Peng
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Jianlin Lei
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China. .,Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, 100084, China. .,Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
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26
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Serotonin transporter-ibogaine complexes illuminate mechanisms of inhibition and transport. Nature 2019; 569:141-145. [PMID: 31019304 DOI: 10.1038/s41586-019-1135-1] [Citation(s) in RCA: 154] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 03/25/2019] [Indexed: 11/09/2022]
Abstract
The serotonin transporter (SERT) regulates neurotransmitter homeostasis through the sodium- and chloride-dependent recycling of serotonin into presynaptic neurons1-3. Major depression and anxiety disorders are treated using selective serotonin reuptake inhibitors-small molecules that competitively block substrate binding and thereby prolong neurotransmitter action2,4. The dopamine and noradrenaline transporters, together with SERT, are members of the neurotransmitter sodium symporter (NSS) family. The transport activities of NSSs can be inhibited or modulated by cocaine and amphetamines2,3, and genetic variants of NSSs are associated with several neuropsychiatric disorders including attention deficit hyperactivity disorder, autism and bipolar disorder2,5. Studies of bacterial NSS homologues-including LeuT-have shown how their transmembrane helices (TMs) undergo conformational changes during the transport cycle, exposing a central binding site to either side of the membrane1,6-12. However, the conformational changes associated with transport in NSSs remain unknown. To elucidate structure-based mechanisms for transport in SERT we investigated its complexes with ibogaine, a hallucinogenic natural product with psychoactive and anti-addictive properties13,14. Notably, ibogaine is a non-competitive inhibitor of transport but displays competitive binding towards selective serotonin reuptake inhibitors15,16. Here we report cryo-electron microscopy structures of SERT-ibogaine complexes captured in outward-open, occluded and inward-open conformations. Ibogaine binds to the central binding site, and closure of the extracellular gate largely involves movements of TMs 1b and 6a. Opening of the intracellular gate involves a hinge-like movement of TM1a and the partial unwinding of TM5, which together create a permeation pathway that enables substrate and ion diffusion to the cytoplasm. These structures define the structural rearrangements that occur from the outward-open to inward-open conformations, and provide insight into the mechanism of neurotransmitter transport and ibogaine inhibition.
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27
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Abstract
Cryogenic electron microscopy (cryo-EM) enables structure determination of macromolecular objects and their assemblies. Although the techniques have been developing for nearly four decades, they have gained widespread attention in recent years due to technical advances on numerous fronts, enabling traditional microscopists to break into the world of molecular structural biology. Many samples can now be routinely analyzed at near-atomic resolution using standard imaging and image analysis techniques. However, numerous challenges to conventional workflows remain, and continued technical advances open entirely novel opportunities for discovery and exploration. Here, I will review some of the main methods surrounding cryo-EM with an emphasis specifically on single-particle analysis, and I will highlight challenges, open questions, and opportunities for methodology development.
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Affiliation(s)
- Dmitry Lyumkis
- From the Laboratory of Genetics and Helmsley Center for Genomic Medicine, The Salk Institute for Biological Studies, La Jolla, California 92037
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