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Gupta LK, Molla J, Prabhu AA. Story of Pore-Forming Proteins from Deadly Disease-Causing Agents to Modern Applications with Evolutionary Significance. Mol Biotechnol 2024; 66:1327-1356. [PMID: 37294530 DOI: 10.1007/s12033-023-00776-1] [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: 01/03/2023] [Accepted: 05/21/2023] [Indexed: 06/10/2023]
Abstract
Animal venoms are a complex mixture of highly specialized toxic molecules. Among them, pore-forming proteins (PFPs) or toxins (PFTs) are one of the major disease-causing toxic elements. The ability of the PFPs in defense and toxicity through pore formation on the host cell surface makes them unique among the toxin proteins. These features made them attractive for academic and research purposes for years in the areas of microbiology as well as structural biology. All the PFPs share a common mechanism of action for the attack of host cells and pore formation in which the selected pore-forming motifs of the host cell membrane-bound protein molecules drive to the lipid bilayer of the cell membrane and eventually produces water-filled pores. But surprisingly their sequence similarity is very poor. Their existence can be seen both in a soluble state and also in transmembrane complexes in the cell membrane. PFPs are prevalent toxic factors that are predominately produced by all kingdoms of life such as virulence bacteria, nematodes, fungi, protozoan parasites, frogs, plants, and also from higher organisms. Nowadays, multiple approaches to applications of PFPs have been conducted by researchers both in basic as well as applied biological research. Although PFPs are very devastating for human health nowadays researchers have been successful in making these toxic proteins into therapeutics through the preparation of immunotoxins. We have discussed the structural, and functional mechanism of action, evolutionary significance through dendrogram, domain organization, and practical applications for various approaches. This review aims to emphasize the PFTs to summarize toxic proteins together for basic knowledge as well as to highlight the current challenges, and literature gap along with the perspective of promising biotechnological applications for their future research.
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Affiliation(s)
- Laxmi Kumari Gupta
- Bioprocess Development Laboratory, Department of Biotechnology, National Institute of Technology Warangal, Warangal, Telangana, 506004, India
| | - Johiruddin Molla
- Ghatal Rabindra Satabarsiki Mahavidyalaya Ghatal, Paschim Medinipur, Ghatal, West Bengal, 721212, India
| | - Ashish A Prabhu
- Bioprocess Development Laboratory, Department of Biotechnology, National Institute of Technology Warangal, Warangal, Telangana, 506004, India.
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2
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Jana S, Evans EGB, Jang HS, Zhang S, Zhang H, Rajca A, Gordon SE, Zagotta WN, Stoll S, Mehl RA. Ultrafast Bioorthogonal Spin-Labeling and Distance Measurements in Mammalian Cells Using Small, Genetically Encoded Tetrazine Amino Acids. J Am Chem Soc 2023; 145:14608-14620. [PMID: 37364003 PMCID: PMC10440187 DOI: 10.1021/jacs.3c00967] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Site-directed spin-labeling (SDSL)─in combination with double electron-electron resonance (DEER) spectroscopy─has emerged as a powerful technique for determining both the structural states and the conformational equilibria of biomacromolecules. DEER combined with in situ SDSL in live cells is challenging since current bioorthogonal labeling approaches are too slow to allow for complete labeling with low concentrations of spin label prior to loss of signal from cellular reduction. Here, we overcome this limitation by genetically encoding a novel family of small, tetrazine-bearing noncanonical amino acids (Tet-v4.0) at multiple sites in proteins expressed in Escherichia coli and in human HEK293T cells. We achieved specific and quantitative spin-labeling of Tet-v4.0-containing proteins by developing a series of strained trans-cyclooctene (sTCO)-functionalized nitroxides─including a gem-diethyl-substituted nitroxide with enhanced stability in cells─with rate constants that can exceed 106 M-1 s-1. The remarkable speed of the Tet-v4.0/sTCO reaction allowed efficient spin-labeling of proteins in live cells within minutes, requiring only sub-micromolar concentrations of sTCO-nitroxide. DEER recorded from intact cells revealed distance distributions in good agreement with those measured from proteins purified and labeled in vitro. Furthermore, DEER was able to resolve the maltose-dependent conformational change of Tet-v4.0-incorporated and spin-labeled MBP in vitro and support assignment of the conformational state of an MBP mutant within HEK293T cells. We anticipate the exceptional reaction rates of this system, combined with the relatively short and rigid side chains of the resulting spin labels, will enable structure/function studies of proteins directly in cells, without any requirements for protein purification.
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Affiliation(s)
- Subhashis Jana
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
| | - Eric G B Evans
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
- Department of Physiology & Biophysics, University of Washington, Seattle, Washington 98195, United States
| | - Hyo Sang Jang
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
| | - Shuyang Zhang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Hui Zhang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Sharona E Gordon
- Department of Physiology & Biophysics, University of Washington, Seattle, Washington 98195, United States
| | - William N Zagotta
- Department of Physiology & Biophysics, University of Washington, Seattle, Washington 98195, United States
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
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3
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Galazzo L, Bordignon E. Electron paramagnetic resonance spectroscopy in structural-dynamic studies of large protein complexes. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2023; 134-135:1-19. [PMID: 37321755 DOI: 10.1016/j.pnmrs.2022.11.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 11/11/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Macromolecular protein assemblies are of fundamental importance for many processes inside the cell, as they perform complex functions and constitute central hubs where reactions occur. Generally, these assemblies undergo large conformational changes and cycle through different states that ultimately are connected to specific functions further regulated by additional small ligands or proteins. Unveiling the 3D structural details of these assemblies at atomic resolution, identifying the flexible parts of the complexes, and monitoring with high temporal resolution the dynamic interplay between different protein regions under physiological conditions is key to fully understanding their properties and to fostering biomedical applications. In the last decade, we have seen remarkable advances in cryo-electron microscopy (EM) techniques, which deeply transformed our vision of structural biology, especially in the field of macromolecular assemblies. With cryo-EM, detailed 3D models of large macromolecular complexes in different conformational states became readily available at atomic resolution. Concomitantly, nuclear magnetic resonance (NMR) and electron paramagnetic resonance spectroscopy (EPR) have benefited from methodological innovations which also improved the quality of the information that can be achieved. Such enhanced sensitivity widened their applicability to macromolecular complexes in environments close to physiological conditions and opened a path towards in-cell applications. In this review we will focus on the advantages and challenges of EPR techniques with an integrative approach towards a complete understanding of macromolecular structures and functions.
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Affiliation(s)
- Laura Galazzo
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Genève 4, Switzerland.
| | - Enrica Bordignon
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Genève 4, Switzerland.
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4
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Jana S, Evans EGB, Jang HS, Zhang S, Zhang H, Rajca A, Gordon SE, Zagotta WN, Stoll S, Mehl RA. Ultra-Fast Bioorthogonal Spin-Labeling and Distance Measurements in Mammalian Cells Using Small, Genetically Encoded Tetrazine Amino Acids. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.26.525763. [PMID: 36747808 PMCID: PMC9901033 DOI: 10.1101/2023.01.26.525763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Studying protein structures and dynamics directly in the cellular environments in which they function is essential to fully understand the molecular mechanisms underlying cellular processes. Site-directed spin-labeling (SDSL)-in combination with double electron-electron resonance (DEER) spectroscopy-has emerged as a powerful technique for determining both the structural states and the conformational equilibria of biomacromolecules. In-cell DEER spectroscopy on proteins in mammalian cells has thus far not been possible due to the notable challenges of spin-labeling in live cells. In-cell SDSL requires exquisite biorthogonality, high labeling reaction rates and low background signal from unreacted residual spin label. While the bioorthogonal reaction must be highly specific and proceed under physiological conditions, many spin labels display time-dependent instability in the reducing cellular environment. Additionally, high concentrations of spin label can be toxic. Thus, an exceptionally fast bioorthogonal reaction is required that can allow for complete labeling with low concentrations of spin-label prior to loss of signal. Here we utilized genetic code expansion to site-specifically encode a novel family of small, tetrazine-bearing non-canonical amino acids (Tet-v4.0) at multiple sites in green fluorescent protein (GFP) and maltose binding protein (MBP) expressed both in E. coli and in human HEK293T cells. We achieved specific and quantitative spin-labeling of Tet-v4.0-containing proteins by developing a series of strained trans -cyclooctene (sTCO)-functionalized nitroxides-including a gem -diethyl-substituted nitroxide with enhanced stability in cells-with rate constants that can exceed 10 6 M -1 s -1 . The remarkable speed of the Tet-v4.0/sTCO reaction allowed efficient spin-labeling of proteins in live HEK293T cells within minutes, requiring only sub-micromolar concentrations of sTCO-nitroxide added directly to the culture medium. DEER recorded from intact cells revealed distance distributions in good agreement with those measured from proteins purified and labeled in vitro . Furthermore, DEER was able to resolve the maltose-dependent conformational change of Tet-v4.0-incorporated and spin-labeled MBP in vitro and successfully discerned the conformational state of MBP within HEK293T cells. We anticipate the exceptional reaction rates of this system, combined with the relatively short and rigid side chains of the resulting spin labels, will enable structure/function studies of proteins directly in cells, without any requirements for protein purification. TOC
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Affiliation(s)
- Subhashis Jana
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
- Equal contributors
| | - Eric G B Evans
- Department of Chemistry, University of Washington, Seattle, WA 98195, United States
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, United States
- Equal contributors
| | - Hyo Sang Jang
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
| | - Shuyang Zhang
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Hui Zhang
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Sharona E Gordon
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, United States
| | - William N Zagotta
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, United States
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, WA 98195, United States
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
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5
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Pierro A, Drescher M. Dance with spins: site-directed spin labeling coupled to electron paramagnetic resonance spectroscopy directly inside cells. Chem Commun (Camb) 2023; 59:1274-1284. [PMID: 36633152 PMCID: PMC9890500 DOI: 10.1039/d2cc05907j] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/04/2023] [Indexed: 01/06/2023]
Abstract
Depicting how biomolecules move and interact within their physiological environment is one of the hottest topics of structural biology. This Feature Article gives an overview of the most recent advances in Site-directed Spin Labeling coupled to Electron Paramagnetic Resonance spectroscopy (SDSL-EPR) to study biomolecules in living cells. The high sensitivity, the virtual absence of background, and the versatility of spin-labeling strategies make this approach one of the most promising techniques for the study of biomolecules in physiologically relevant environments. After presenting the milestones achieved in this field, we present a summary of the future goals and ambitions of this community.
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Affiliation(s)
- Annalisa Pierro
- Department of Chemistry, University of Konstanz, and Konstanz Research School Chemical Biology, Universitätsstraße 10, 78457 Konstanz, Germany.
| | - Malte Drescher
- Department of Chemistry, University of Konstanz, and Konstanz Research School Chemical Biology, Universitätsstraße 10, 78457 Konstanz, Germany.
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6
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Goldfarb D. Exploring protein conformations in vitro and in cell with EPR distance measurements. Curr Opin Struct Biol 2022; 75:102398. [PMID: 35667279 DOI: 10.1016/j.sbi.2022.102398] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/20/2022] [Accepted: 04/30/2022] [Indexed: 11/18/2022]
Abstract
The electron-electron double resonance (DEER) method, which provides distance distributions between two spin labels, attached site specifically to biomolecules (proteins and nucleic acids), is currently a well-recognized biophysical tool in structural biology. The most commonly used spin labels are based on nitroxide stable radicals, conjugated to the proteins primarily via native or engineered cysteine residues. However, in recent years, new spin labels, along with different labeling chemistries, have been introduced, driven in part by the desire to study structural and dynamical properties of biomolecules in their native environment, the cell. This mini-review focuses on these new spin labels, which allow for DEER on orthogonal spin labels, and on the state of the art methods for in-cell DEER distance measurements.
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Affiliation(s)
- Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 761001, Israel
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7
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Ulhuq FR, Mariano G. Bacterial pore-forming toxins. MICROBIOLOGY (READING, ENGLAND) 2022; 168:001154. [PMID: 35333704 PMCID: PMC9558359 DOI: 10.1099/mic.0.001154] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/03/2022] [Indexed: 12/11/2022]
Abstract
Pore-forming toxins (PFTs) are widely distributed in both Gram-negative and Gram-positive bacteria. PFTs can act as virulence factors that bacteria utilise in dissemination and host colonisation or, alternatively, they can be employed to compete with rival microbes in polymicrobial niches. PFTs transition from a soluble form to become membrane-embedded by undergoing large conformational changes. Once inserted, they perforate the membrane, causing uncontrolled efflux of ions and/or nutrients and dissipating the protonmotive force (PMF). In some instances, target cells intoxicated by PFTs display additional effects as part of the cellular response to pore formation. Significant progress has been made in the mechanistic description of pore formation for the different PFTs families, but in several cases a complete understanding of pore structure remains lacking. PFTs have evolved recognition mechanisms to bind specific receptors that define their host tropism, although this can be remarkably diverse even within the same family. Here we summarise the salient features of PFTs and highlight where additional research is necessary to fully understand the mechanism of pore formation by members of this diverse group of protein toxins.
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Affiliation(s)
- Fatima R. Ulhuq
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
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8
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Sannigrahi A, Chattopadhyay K. Pore formation by pore forming membrane proteins towards infections. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:79-111. [PMID: 35034727 DOI: 10.1016/bs.apcsb.2021.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Over the last 25 years, the biology of membrane proteins, including the PFPs-membranes interactions is seeking attention for the development of successful drug molecules against a number of infectious diseases. Pore forming toxins (PFTs), the largest family of PFPs are considered as a group of virulence factors produced in a large number of pathogenic systems which include streptococcus, pneumonia, Staphylococcus aureus, E. coli, Mycobacterium tuberculosis, group A and B streptococci, Corynebacterium diphtheria and many more. PFTs are generally utilized by the disease causing pathogens to disrupt the host first line of defense i.e. host cell membranes through pore formation strategy. Although, pore formation is the principal mode of action of the PFTs but they can have additional adverse effects on the hosts including immune evasion. Recently, structural investigation of different PFTs have imparted the molecular mechanistic insights into how PFTs get transformed from its inactive state to active toxic state. On the basis of their structural entity, PFTs have been classified in different types and their mode of actions alters in terms of pore formation and corresponding cellular toxicity. Although pathogen genome analysis can identify the probable PFTs depending upon their structural diversity, there are so many PFTs which utilize the local environmental conditions to generate their pore forming ability using a novel strategy which is known as "conformational switch" of a protein. This conformational switch is considered as characteristics of the phase shifting proteins which were often utilized by many pathogenic systems to protect them from the invaders through allosteric communication between distant regions of the protein. In this chapter, we discuss the structure function relationships of PFTs and how activity of PFTs varies with the change in the environmental conditions has been explored. Finally, we demonstrate these structural insights to develop therapeutic potential to treat the infections caused by multidrug resistant pathogens.
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Affiliation(s)
- Achinta Sannigrahi
- Department of Chemical Engineering, Indian Institute of Science, Bengaluru, Karnataka, India.
| | - Krishnananda Chattopadhyay
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India.
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Mondal AK, Chattopadhyay K. Structures and functions of the membrane-damaging pore-forming proteins. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:241-288. [PMID: 35034720 DOI: 10.1016/bs.apcsb.2021.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Pore-forming proteins (PFPs) of the diverse life forms have emerged as the potent cell-killing entities owing to their specialized membrane-damaging properties. PFPs have the unique ability to perforate the plasma membranes of their target cells, and they exert this functionality by creating oligomeric pores in the membrane lipid bilayer. Pathogenic bacteria employ PFPs as toxins to execute their virulence mechanisms, whereas in the higher vertebrates PFPs are deployed as the part of the immune system and to generate inflammatory responses. PFPs are the unique dimorphic proteins that are generally synthesized as water-soluble molecules, and transform into membrane-inserted oligomeric pore assemblies upon interacting with the target membranes. In spite of sharing very little sequence similarity, PFPs from diverse organisms display incredible structural similarity. Yet, at the same time, structure-function mechanisms of the PFPs document remarkable versatility. Such notions establish PFPs as the fascinating model system to explore variety of unsolved issues pertaining to the structure-function paradigm of the proteins that interact and act in the membrane environment. In this article, we discuss our current understanding regarding the structural basis of the pore-forming functions of the diverse class of PFPs. We attempt to highlight the similarities and differences in their structures, membrane pore-formation mechanisms, and their implications for the various biological processes, ranging from the bacterial virulence mechanisms to the inflammatory immune response generation in the higher animals.
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Affiliation(s)
- Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India.
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10
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Kucher S, Elsner C, Safonova M, Maffini S, Bordignon E. In-Cell Double Electron-Electron Resonance at Nanomolar Protein Concentrations. J Phys Chem Lett 2021; 12:3679-3684. [PMID: 33829785 DOI: 10.1021/acs.jpclett.1c00048] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is an established technique to site-specifically monitor conformational changes of spin-labeled biomolecules. Emerging in-cell EPR approaches aiming to address spin-labeled proteins in their native environment still struggle to reach a broad applicability and to target physiologically relevant protein concentrations. Here, we present a comparative in vitro and in-cell double electron-electron resonance (DEER) study demonstrating that nanomolar protein concentrations are at reach to measure distances up to 4.5 nm between protein sites carrying commercial gadolinium spin labels.
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Affiliation(s)
- Svetlana Kucher
- Ruhr University Bochum, Faculty of Chemistry and Biochemistry, Universitaetsstr. 150, 44801 Bochum, Germany
| | - Christina Elsner
- Ruhr University Bochum, Faculty of Chemistry and Biochemistry, Universitaetsstr. 150, 44801 Bochum, Germany
| | - Mariya Safonova
- Ruhr University Bochum, Faculty of Chemistry and Biochemistry, Universitaetsstr. 150, 44801 Bochum, Germany
| | - Stefano Maffini
- Max Planck Institute of Molecular Physiology, Department of Mechanistic Cell Biology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
| | - Enrica Bordignon
- Ruhr University Bochum, Faculty of Chemistry and Biochemistry, Universitaetsstr. 150, 44801 Bochum, Germany
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Torricella F, Pierro A, Mileo E, Belle V, Bonucci A. Nitroxide spin labels and EPR spectroscopy: A powerful association for protein dynamics studies. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140653. [PMID: 33757896 DOI: 10.1016/j.bbapap.2021.140653] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/01/2023]
Abstract
Site-Directed Spin Labelling (SDSL) technique is based on the attachment of a paramagnetic label onto a specific position of a protein (or other bio-molecules) and the subsequent study by Electron Paramagnetic Resonance (EPR) spectroscopy. In particular, continuous-wave EPR (cw-EPR) spectra can detect the local conformational dynamics for proteins under various conditions. Moreover, pulse-EPR experiments on doubly spin-labelled proteins allow measuring distances between spin centres in the 1.5-8 nm range, providing information about structures and functions. This review focuses on SDSL-EPR spectroscopy as a structural biology tool to investigate proteins using nitroxide labels. The versatility of this spectroscopic approach for protein structural characterization has been demonstrated through the choice of recent studies. The main aim is to provide a general overview of the technique, particularly for non-experts, to spread the applicability of this technique in various fields of structural biology.
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Affiliation(s)
- F Torricella
- CERM-Magnetic Resonance Center, Department of Chemistry, University of Florence, via L.Sacconi 6, 50019 Sesto Fiorentino, Italy
| | - A Pierro
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France
| | - E Mileo
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France
| | - V Belle
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France
| | - A Bonucci
- CERM-Magnetic Resonance Center, Department of Chemistry, University of Florence, via L.Sacconi 6, 50019 Sesto Fiorentino, Italy; Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France.
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12
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Pore-forming proteins: From defense factors to endogenous executors of cell death. Chem Phys Lipids 2020; 234:105026. [PMID: 33309552 DOI: 10.1016/j.chemphyslip.2020.105026] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 02/06/2023]
Abstract
Pore-forming proteins (PFPs) and small antimicrobial peptides (AMPs) represent a large family of molecules with the common ability to punch holes in cell membranes to alter their permeability. They play a fundamental role as infectious bacteria's defensive tools against host's immune system and as executors of endogenous machineries of regulated cell death in eukaryotic cells. Despite being highly divergent in primary sequence and 3D structure, specific folds of pore-forming domains have been conserved. In fact, pore formation is considered an ancient mechanism that takes place through a general multistep process involving: membrane partitioning and insertion, oligomerization and pore formation. However, different PFPs and AMPs assemble and form pores following different mechanisms that could end up either in the formation of protein-lined or protein-lipid pores. In this review, we analyze the current findings in the mechanism of action of different PFPs and AMPs that support a wide role of membrane pore formation in nature. We also provide the newest insights into the development of state-of-art techniques that have facilitated the characterization of membrane pores. To understand the physiological role of these peptides/proteins or develop clinical applications, it is essential to uncover the molecular mechanism of how they perforate membranes.
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13
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Jaiswal M, Tran TT, Li Q, Yan X, Zhou M, Kundu K, Fanucci GE, Guo Z. A metabolically engineered spin-labeling approach for studying glycans on cells. Chem Sci 2020; 11:12522-12532. [PMID: 34094453 PMCID: PMC8162880 DOI: 10.1039/d0sc03874a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/14/2020] [Indexed: 11/30/2022] Open
Abstract
Metabolic glycan engineering (MGE) coupled with nitroxide spin-labeling (SL) was utilized to investigate the heterogeneous environment of cell surface glycans in select cancer and normal cells. This approach exploited the incorporation of azides into cell surface glycans followed by a click reaction with a new nitroxide spin label. Both sialic acid and N-acetylglucosamine (GlcNAc) were targeted for spin labelling. Although each of these moieties experiences a diverse and heterogeneous glycan environment, their EPR spectra and hence mobility are both characterized as a linear combination of two distinct spectra where one component reflects a highly mobile or uncrowded micro-environment with the second component reflecting more restricted motion, reflective of increased crowding and packing within the glycocalyx. What differs among the spectra of the targeted glycans is the relative percentage of each component, with sialic acid moieties experiencing on average an ∼80% less crowded environment, where conversely GlcNAc/GalNAz labeled sites reported on average a ∼50% more crowded environment. These distinct environments are consistent with the organization of sugar moieties within cellular glycans where some residues occur close to the cell membrane/protein backbone (i.e. more restricted) and others are more terminal in the glycan (i.e. more mobile). Strikingly, different cell lines displayed varied relative populations of these two components, suggesting distinctive glycan packing, organization, and composition of different cells. This work demonstrates the capability of SDSL EPR to be a broadly useful tool for studying glycans on cells, and interpretation of the results provides insights for distinguishing the differences and changes in the local organization and heterogeneity of the cellular glycocalyx.
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Affiliation(s)
- Mohit Jaiswal
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Trang T Tran
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Qingjiang Li
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Xin Yan
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Mingwei Zhou
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Krishnendu Kundu
- National High Magnetic Field Laboratory, Florida State University Tallahassee Florida 32310 USA
| | - Gail E Fanucci
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
| | - Zhongwu Guo
- Department of Chemistry, University of Florida 214 Leigh Hall Gainesville FL 32611 USA
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14
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Kucher S, Korneev S, Klare JP, Klose D, Steinhoff HJ. In cell Gd3+-based site-directed spin labeling and EPR spectroscopy of eGFP. Phys Chem Chem Phys 2020; 22:13358-13362. [DOI: 10.1039/d0cp01930e] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A newly synthesized Gd3+ chelate complex allows in cell spin labeling and detection of eGFP by EPR spectroscopy.
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Affiliation(s)
| | - Sergej Korneev
- Department of Biology
- Osnabrück University
- Osnabrück
- Germany
| | | | - Daniel Klose
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- Zurich
- Switzerland
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15
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Widder P, Schuck J, Summerer D, Drescher M. Combining site-directed spin labeling in vivo and in-cell EPR distance determination. Phys Chem Chem Phys 2020; 22:4875-4879. [DOI: 10.1039/c9cp05584c] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Non-canonical amino acid incorporation via amber stop codon suppression and in vivo site-directed spin labeling allow in-cell EPR distance determination in E. coli.
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Affiliation(s)
- Pia Widder
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB)
- University of Konstanz
- Konstanz
- Germany
| | - Julian Schuck
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB)
- University of Konstanz
- Konstanz
- Germany
| | - Daniel Summerer
- Faculty of Chemistry and Chemical Biology
- TU Dortmund University
- Dortmund
- Germany
| | - Malte Drescher
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB)
- University of Konstanz
- Konstanz
- Germany
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16
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Mariano G, Trunk K, Williams DJ, Monlezun L, Strahl H, Pitt SJ, Coulthurst SJ. A family of Type VI secretion system effector proteins that form ion-selective pores. Nat Commun 2019; 10:5484. [PMID: 31792213 PMCID: PMC6889166 DOI: 10.1038/s41467-019-13439-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/05/2019] [Indexed: 12/25/2022] Open
Abstract
Type VI secretion systems (T6SSs) are nanomachines widely used by bacteria to deliver toxic effector proteins directly into neighbouring cells. However, the modes of action of many effectors remain unknown. Here we report that Ssp6, an anti-bacterial effector delivered by a T6SS of the opportunistic pathogen Serratia marcescens, is a toxin that forms ion-selective pores. Ssp6 inhibits bacterial growth by causing depolarisation of the inner membrane in intoxicated cells, together with increased outer membrane permeability. Reconstruction of Ssp6 activity in vitro demonstrates that it forms cation-selective pores. A survey of bacterial genomes reveals that genes encoding Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 and similar proteins represent a new family of T6SS-delivered anti-bacterial effectors.
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Affiliation(s)
- Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Katharina Trunk
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - David J Williams
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Laura Monlezun
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Newcastle University, Richardson Road, Newcastle-upon-Tyne, NE2 4AX, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK.
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17
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Duport C, Alpha-Bazin B, Armengaud J. Advanced Proteomics as a Powerful Tool for Studying Toxins of Human Bacterial Pathogens. Toxins (Basel) 2019; 11:toxins11100576. [PMID: 31590258 PMCID: PMC6832400 DOI: 10.3390/toxins11100576] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 09/27/2019] [Accepted: 09/30/2019] [Indexed: 12/15/2022] Open
Abstract
Exotoxins contribute to the infectious processes of many bacterial pathogens, mainly by causing host tissue damages. The production of exotoxins varies according to the bacterial species. Recent advances in proteomics revealed that pathogenic bacteria are capable of simultaneously producing more than a dozen exotoxins. Interestingly, these toxins may be subject to post-transcriptional modifications in response to environmental conditions. In this review, we give an outline of different bacterial exotoxins and their mechanism of action. We also report how proteomics contributed to immense progress in the study of toxinogenic potential of pathogenic bacteria over the last two decades.
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Affiliation(s)
- Catherine Duport
- SQPOV, UMR0408, Avignon Université, INRA, F-84914 Avignon, France
- Correspondence:
| | - Béatrice Alpha-Bazin
- Laboratoire Innovations technologiques pour la Détection et le Diagnostic (Li2D), Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, F-30207 Bagnols sur Cèze, France; (B.A.-B.); (J.A.)
| | - Jean Armengaud
- Laboratoire Innovations technologiques pour la Détection et le Diagnostic (Li2D), Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, F-30207 Bagnols sur Cèze, France; (B.A.-B.); (J.A.)
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18
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Bonucci A, Ouari O, Guigliarelli B, Belle V, Mileo E. In‐Cell EPR: Progress towards Structural Studies Inside Cells. Chembiochem 2019; 21:451-460. [DOI: 10.1002/cbic.201900291] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Alessio Bonucci
- Magnetic Resonance CenterCERMUniversity of Florence 50019 Sesto Fiorentino Italy
| | - Olivier Ouari
- Aix Marseille UnivCNRSICRInstitut de Chimie Radicalaire 13013 Marseille France
| | - Bruno Guigliarelli
- Aix Marseille UnivCNRSBIPBioénergétique et Ingénierie des ProtéinesIMM 13009 Marseille France
| | - Valérie Belle
- Aix Marseille UnivCNRSBIPBioénergétique et Ingénierie des ProtéinesIMM 13009 Marseille France
| | - Elisabetta Mileo
- Aix Marseille UnivCNRSBIPBioénergétique et Ingénierie des ProtéinesIMM 13009 Marseille France
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19
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A new perspective on membrane-embedded Bax oligomers using DEER and bioresistant orthogonal spin labels. Sci Rep 2019; 9:13013. [PMID: 31506457 PMCID: PMC6737250 DOI: 10.1038/s41598-019-49370-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 08/20/2019] [Indexed: 12/23/2022] Open
Abstract
Bax is a Bcl-2 protein crucial for apoptosis initiation and execution, whose active conformation is only partially understood. Dipolar EPR spectroscopy has proven to be a valuable tool to determine coarse-grained models of membrane-embedded Bcl-2 proteins. Here we show how the combination of spectroscopically distinguishable nitroxide and gadolinium spin labels and Double Electron-Electron Resonance can help to gain new insights into the quaternary structure of active, membrane-embedded Bax oligomers. We show that attaching labels bulkier than the conventional MTSL may affect Bax fold and activity, depending on the protein/label combination. However, we identified a suitable pair of spectroscopically distinguishable labels, which allows to study complex distance networks in the oligomers that could not be disentangled before. Additionally, we compared the stability of the different spin-labeled protein variants in E. coli and HeLa cell extracts. We found that the gem-diethyl nitroxide-labeled Bax variants were reasonably stable in HeLa cell extracts. However, when transferred into human cells, Bax was found to be mislocalized, thus preventing its characterization in a physiological environment. The successful use of spectroscopically distinguishable labels on membrane-embedded Bax-oligomers opens an exciting new path towards structure determination of membrane-embedded homo- or hetero-oligomeric Bcl-2 proteins via EPR.
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20
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Bleicken S, Assafa TE, Zhang H, Elsner C, Ritsch I, Pink M, Rajca S, Jeschke G, Rajca A, Bordignon E. gem-Diethyl Pyrroline Nitroxide Spin Labels: Synthesis, EPR Characterization, Rotamer Libraries and Biocompatibility. ChemistryOpen 2019; 8:1057-1065. [PMID: 31463171 PMCID: PMC6709561 DOI: 10.1002/open.201900119] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Indexed: 12/29/2022] Open
Abstract
The availability of bioresistant spin labels is crucial for the optimization of site-directed spin labeling protocols for EPR structural studies of biomolecules in a cellular context. As labeling can affect proteins' fold and/or function, having the possibility to choose between different spin labels will increase the probability to produce spin-labeled functional proteins. Here, we report the synthesis and characterization of iodoacetamide- and maleimide-functionalized spin labels based on the gem-diethyl pyrroline structure. The two nitroxide labels are compared to conventional gem-dimethyl analogs by site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy, using two water soluble proteins: T4 lysozyme and Bid. To foster their use for structural studies, we also present rotamer libraries for these labels, compatible with the MMM software. Finally, we investigate the "true" biocompatibility of the gem-diethyl probes comparing the resistance towards chemical reduction of the NO group in ascorbate solutions and E. coli cytosol at different spin concentrations.
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Affiliation(s)
- Stephanie Bleicken
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
- ZEMOSRuhr University BochumUniversitaetsstrasse 150, 44801BochumGermany
| | - Tufa E. Assafa
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
| | - Hui Zhang
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Christina Elsner
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
| | - Irina Ritsch
- ETH ZurichLaboratory of Physical ChemistryVladimir-Prelog-Weg 2CH-8093ZurichSwitzerland.
| | - Maren Pink
- IUMSC, Department of ChemistryIndiana UniversityBloomington, Indiana47405-7102USA
| | - Suchada Rajca
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Gunnar Jeschke
- ETH ZurichLaboratory of Physical ChemistryVladimir-Prelog-Weg 2CH-8093ZurichSwitzerland.
| | - Andrzej Rajca
- Department of ChemistryUniversity of Nebraska, LincolnNebraska68588-0304USA
| | - Enrica Bordignon
- Faculty of Chemistry and BiochemistryRuhr University Bochum, Universitaetsstrasse 15044801BochumGermany
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21
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Joseph B, Jaumann EA, Sikora A, Barth K, Prisner TF, Cafiso DS. In situ observation of conformational dynamics and protein ligand-substrate interactions in outer-membrane proteins with DEER/PELDOR spectroscopy. Nat Protoc 2019; 14:2344-2369. [PMID: 31278399 PMCID: PMC6886689 DOI: 10.1038/s41596-019-0182-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 04/18/2019] [Indexed: 12/01/2022]
Abstract
Observing structure and conformational dynamics of membrane proteins at high-resolution in their native environments is challenging because of the lack of suitable techniques. We have developed an approach for high-precision distance measurements in the nanometer range for outer membrane proteins (OMPs) in intact E. coli and native membranes. OMPs in Gram-negative bacteria rarely have reactive cysteines. This enables in-situ labeling of engineered cysteines with a methanethiosulfonate functionalized nitroxide spin label (MTSL) with minimal background signals. Following overexpression of the target protein, spin labeling is performed with E. coli or isolated outer membranes (OM) under selective conditions. The interspin distances are measured in-situ using pulsed electron-electron double resonance spectroscopy (PELDOR or DEER). The residual background signals, which are problematic for in-situ structural biology, contributes specifically to the intermolecular part of the signal and can be selectively removed to extract the desired interspin distance distribution. The initial cloning stage can take 5–7 d and the subsequent protein expression, OM isolation, spin labeling, PELDOR experiment, and the data analysis typically take 4–5 d. The described protocol provides a general strategy for observing protein-ligand/substrate interactions, oligomerization, and conformational dynamics of OMPs in the native OM and intact E. coli. EDITORIAL SUMMARY This protocol describes how to label bacterial outer membrane proteins with spin labels to study conformational changes and their interaction with ligands and substrates in native membranes and cells using Pulsed Electron-Electron Double Resonance (PELDOR or DEER) spectroscopy. TWEET A new protocol for studying conformational changes and ligand/substrate interactions of bacterial outer membrane proteins in-situ. COVER TEASER Studying membrane protein conformations in-situ
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Affiliation(s)
- Benesh Joseph
- Institute of Biophysics, Department of Physics, University of Frankfurt, Frankfurt am Main, Germany. .,Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Frankfurt am Main, Germany.
| | - Eva A Jaumann
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Frankfurt am Main, Germany
| | - Arthur Sikora
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, VA, USA
| | - Katja Barth
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Frankfurt am Main, Germany
| | - Thomas F Prisner
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Frankfurt am Main, Germany
| | - David S Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, VA, USA
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22
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Abstract
AbstractThe dynamics of proteins in solution includes a variety of processes, such as backbone and side-chain fluctuations, interdomain motions, as well as global rotational and translational (i.e. center of mass) diffusion. Since protein dynamics is related to protein function and essential transport processes, a detailed mechanistic understanding and monitoring of protein dynamics in solution is highly desirable. The hierarchical character of protein dynamics requires experimental tools addressing a broad range of time- and length scales. We discuss how different techniques contribute to a comprehensive picture of protein dynamics, and focus in particular on results from neutron spectroscopy. We outline the underlying principles and review available instrumentation as well as related analysis frameworks.
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23
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Glasbrenner M, Vogler S, Ochsenfeld C. Gauge-origin dependence in electronic g-tensor calculations. J Chem Phys 2018; 148:214101. [DOI: 10.1063/1.5028454] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Michael Glasbrenner
- Chair of Theoretical Chemistry and Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, 81377 Munich, Germany
| | - Sigurd Vogler
- Chair of Theoretical Chemistry and Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, 81377 Munich, Germany
| | - Christian Ochsenfeld
- Chair of Theoretical Chemistry and Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, 81377 Munich, Germany
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24
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Uren RT, Iyer S, Kluck RM. Pore formation by dimeric Bak and Bax: an unusual pore? Philos Trans R Soc Lond B Biol Sci 2018. [PMID: 28630157 DOI: 10.1098/rstb.2016.0218] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Apoptotic cell death via the mitochondrial pathway occurs in all vertebrate cells and requires the formation of pores in the mitochondrial outer membrane. Two Bcl-2 protein family members, Bak and Bax, form these pores during apoptosis, and how they do so has been investigated for the last two decades. Many of the conformation changes that occur during their transition to pore-forming proteins have now been delineated. Notably, biochemical, biophysical and structural studies indicate that symmetric homodimers are the basic unit of pore formation. Each dimer contains an extended hydrophobic surface that lies on the outer membrane, and is anchored at either end by a transmembrane domain. Membrane-remodelling events such as positive membrane curvature have been reported to accompany apoptotic pore formation, suggesting Bak and Bax form lipidic pores rather than proteinaceous pores. However, it remains unclear how symmetric dimers assemble to porate the membrane. Here, we review how clusters of dimers and their lipid-mediated interactions provide a molecular explanation for the heterogeneous assemblies of Bak and Bax observed during apoptosis.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
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Affiliation(s)
- Rachel T Uren
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Sweta Iyer
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Ruth M Kluck
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia .,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
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25
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Karthikeyan G, Bonucci A, Casano G, Gerbaud G, Abel S, Thomé V, Kodjabachian L, Magalon A, Guigliarelli B, Belle V, Ouari O, Mileo E. A Bioresistant Nitroxide Spin Label for In-Cell EPR Spectroscopy: In Vitro and In Oocytes Protein Structural Dynamics Studies. Angew Chem Int Ed Engl 2018; 57:1366-1370. [DOI: 10.1002/anie.201710184] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/07/2017] [Indexed: 01/28/2023]
Affiliation(s)
- Ganesan Karthikeyan
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Alessio Bonucci
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Gilles Casano
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Guillaume Gerbaud
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Sébastien Abel
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Virginie Thomé
- Aix Marseille Univ, CNRS, IBDM; Institut de Biologie du Développement de Marseille; Marseille France
| | - Laurent Kodjabachian
- Aix Marseille Univ, CNRS, IBDM; Institut de Biologie du Développement de Marseille; Marseille France
| | - Axel Magalon
- Aix Marseille Univ, CNRS, LCB; Laboratoire de Chimie Bactérienne; Marseille France
| | - Bruno Guigliarelli
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Valérie Belle
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Olivier Ouari
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Elisabetta Mileo
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
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26
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Karthikeyan G, Bonucci A, Casano G, Gerbaud G, Abel S, Thomé V, Kodjabachian L, Magalon A, Guigliarelli B, Belle V, Ouari O, Mileo E. A Bioresistant Nitroxide Spin Label for In-Cell EPR Spectroscopy: In Vitro and In Oocytes Protein Structural Dynamics Studies. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201710184] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Ganesan Karthikeyan
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Alessio Bonucci
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Gilles Casano
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Guillaume Gerbaud
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Sébastien Abel
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Virginie Thomé
- Aix Marseille Univ, CNRS, IBDM; Institut de Biologie du Développement de Marseille; Marseille France
| | - Laurent Kodjabachian
- Aix Marseille Univ, CNRS, IBDM; Institut de Biologie du Développement de Marseille; Marseille France
| | - Axel Magalon
- Aix Marseille Univ, CNRS, LCB; Laboratoire de Chimie Bactérienne; Marseille France
| | - Bruno Guigliarelli
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Valérie Belle
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
| | - Olivier Ouari
- Aix Marseille Univ, CNRS, ICR; Institut de Chimie Radicalaire; Marseille France
| | - Elisabetta Mileo
- Aix Marseille Univ, CNRS, BIP; Laboratoire de Bioénergétique et Ingénierie des Protéines; Marseille France
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27
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Lawless MJ, Shimshi A, Cunningham TF, Kinde MN, Tang P, Saxena S. Analysis of Nitroxide-Based Distance Measurements in Cell Extracts and in Cells by Pulsed ESR Spectroscopy. Chemphyschem 2017; 18:1653-1660. [PMID: 28295910 DOI: 10.1002/cphc.201700115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Indexed: 11/10/2022]
Abstract
Measurements of distances in cells by pulsed ESR spectroscopy afford tremendous opportunities to study proteins in native environments that are irreproducible in vitro. However, the in-cell environment is harsh towards the typical nitroxide radicals used in double electron-electron resonance (DEER) experiments. A systematic examination is performed on the loss of the DEER signal, including contributions from nitroxide decay and nitroxide side-chain cleavage. In addition, the possibility of extending the lifetime of the nitroxide radical by use of an oxidizing agent is investigated. Using this oxidizing agent, DEER distance measurements are performed on doubly nitroxide-labeled GB1, the immunoglobulin-binding domain of protein G, at varying incubation times in the cellular environment. It is found that, by comparison of the loss of DEER signal to the loss of the CW spectrum, cleavage of the nitroxide side chain contributes to the loss of DEER signal, which is significantly greater in cells than in cell extracts. Finally, local spin concentrations are monitored at varying incubation times to show the time required for molecular diffusion of a small globular protein within the cellular milieu.
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Affiliation(s)
- Matthew J Lawless
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
| | - Amit Shimshi
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
| | - Timothy F Cunningham
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA.,Current address: Department of Chemistry, Hanover College, 484 Ball Dr, Hanover, IN, 47243, USA
| | - Monica N Kinde
- Department of Anesthesiology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA, 15213, USA.,Current address: Division of Basic Sciences, Kansas City University of Medicine and Biosciences, 2901 St. John's Blvd., Joplin, MO, 64804, USA
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA, 15213, USA
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
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28
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Kucher S, Korneev S, Tyagi S, Apfelbaum R, Grohmann D, Lemke EA, Klare JP, Steinhoff HJ, Klose D. Orthogonal spin labeling using click chemistry for in vitro and in vivo applications. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 275:38-45. [PMID: 27992783 DOI: 10.1016/j.jmr.2016.12.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 06/06/2023]
Abstract
Site-directed spin labeling for EPR- and NMR spectroscopy has mainly been achieved exploiting the specific reactivity of cysteines. For proteins with native cysteines or for in vivo applications, an alternative coupling strategy is required. In these cases click chemistry offers major benefits by providing a fast and highly selective, biocompatible reaction between azide and alkyne groups. Here, we establish click chemistry as a tool to target unnatural amino acids in vitro and in vivo using azide- and alkyne-functionalized spin labels. The approach is compatible with a variety of labels including reduction-sensitive nitroxides. Comparing spin labeling efficiencies from the copper-free with the strongly reducing copper(I)-catalyzed azide-alkyne click reaction, we find that the faster kinetics for the catalyzed reaction outrun reduction of the labile nitroxide spin labels and allow quantitative labeling yields within short reaction times. Inter-spin distance measurements demonstrate that the novel side chain is suitable for paramagnetic NMR- or EPR-based conformational studies of macromolecular complexes.
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Affiliation(s)
- Svetlana Kucher
- Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany
| | - Sergei Korneev
- Department of Biology & Chemistry, Barbarastr. 11, 49076 Osnabrück, Germany
| | - Swati Tyagi
- Structural and Computational Biology Unit, Cell Biology and Biophysics Unit, EMBL, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Ronja Apfelbaum
- Physical and Theoretical Chemistry, Technical University of Braunschweig, Hans-Sommer-Str. 10, 38106 Braunschweig, Germany
| | - Dina Grohmann
- Physical and Theoretical Chemistry, Technical University of Braunschweig, Hans-Sommer-Str. 10, 38106 Braunschweig, Germany
| | - Edward A Lemke
- Structural and Computational Biology Unit, Cell Biology and Biophysics Unit, EMBL, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Johann P Klare
- Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany
| | - Heinz-Jürgen Steinhoff
- Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany.
| | - Daniel Klose
- Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany.
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Meenakumari V, Utsumi H, Jawahar A, Franklin Benial AM. Concentration dependence of nitroxyl spin probes in liposomal solution: electron spin resonance and overhauser-enhanced magnetic resonance studies. J Liposome Res 2016; 28:87-96. [PMID: 27892752 DOI: 10.1080/08982104.2016.1264960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
In this work, the detailed studies of electron spin resonance (ESR) and overhauser-enhanced magnetic resonance imaging (OMRI) were carried out for permeable nitroxyl spin probe, MC-PROXYL as a function of agent concentration in liposomal solution. In order to compare the impermeable nature of nitroxyl radical, the study was also carried out only at 2 mM concentration of carboxy-PROXYL. The ESR parameters were estimated using L-band and 300 MHz ESR spectrometers. The line width broadening was measured as a function of agent concentration in liposomal solution. The estimated rotational correlation time is proportional to the agent concentration, which indicates that less mobile nature of nitroxyl spin probe in liposomal solution. The partition parameter and permeability values indicate that the diffusion of nitroxyl spin probe distribution into the lipid phase is maximum at 2 mM concentration of MC-PROXYL. The dynamic nuclear polarization (DNP) parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for 2 mM MC-PROXYL in 400 mM liposomal dispersion. The spin lattice relaxation time was shortened in liposomal solution, which leads to the high relaxivity. Reduction in coupling factor is due to less interaction between the electron and nuclear spins, which causes the reduction in enhancement. The leakage factor increases with increasing agent concentration. The increase in DNP enhancement was significant up to 2 mM in liposomal solution. These results paves the way for choosing optimum agent concentration and OMRI scan parameters used in intra and extra membrane water by loading the liposome vesicles with a lipid permeable nitroxyl spin probes in OMRI experiments.
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Affiliation(s)
- V Meenakumari
- a Department of Physics , NMSSVN College , Madurai , Tamilnadu India
| | - Hideo Utsumi
- b Innovation Center for Medical Redox Navigation, Kyushu University , Fukuoka , Japan , and
| | - A Jawahar
- c Department of Chemistry , NMSSVN College , Madurai , Tamilnadu , India
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30
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Joseph B, Tormyshev VM, Rogozhnikova OY, Akhmetzyanov D, Bagryanskaya EG, Prisner TF. Selective High-Resolution Detection of Membrane Protein-Ligand Interaction in Native Membranes Using Trityl-Nitroxide PELDOR. Angew Chem Int Ed Engl 2016; 55:11538-42. [DOI: 10.1002/anie.201606335] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Benesh Joseph
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Victor M. Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
- Novosibirsk State University; Novosibirsk 630090 Russia
| | - Olga Yu. Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Dmitry Akhmetzyanov
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Elena G. Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Thomas F. Prisner
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
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31
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Joseph B, Tormyshev VM, Rogozhnikova OY, Akhmetzyanov D, Bagryanskaya EG, Prisner TF. Selective High-Resolution Detection of Membrane Protein-Ligand Interaction in Native Membranes Using Trityl-Nitroxide PELDOR. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606335] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Benesh Joseph
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Victor M. Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
- Novosibirsk State University; Novosibirsk 630090 Russia
| | - Olga Yu. Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Dmitry Akhmetzyanov
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Elena G. Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Thomas F. Prisner
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
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32
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Aitha M, Moller AJ, Sahu ID, Horitani M, Tierney DL, Crowder MW. Investigating the position of the hairpin loop in New Delhi metallo-β-lactamase, NDM-1, during catalysis and inhibitor binding. J Inorg Biochem 2016; 156:35-9. [PMID: 26717260 PMCID: PMC4843777 DOI: 10.1016/j.jinorgbio.2015.10.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 10/07/2015] [Accepted: 10/19/2015] [Indexed: 12/29/2022]
Abstract
In an effort to examine the relative position of a hairpin loop in New Delhi metallo-β-lactamase, NDM-1, during catalysis, rapid freeze quench double electron electron resonance (RFQ-DEER) spectroscopy was used. A doubly-labeled mutant of NDM-1, which had one spin label on the invariant loop at position 69 and another label at position 235, was prepared and characterized. The reaction of the doubly spin labeled mutant with chromacef was freeze quenched at 500μs and 10ms. DEER results showed that the average distance between labels decreased by 4Å in the 500μs quenched sample and by 2Å in the 10ms quenched sample, as compared to the distance in the unreacted enzyme, although the peaks corresponding to distance distributions were very broad. DEER spectra with the doubly spin labeled enzyme with two inhibitors showed that the distance between the loop residue at position 69 and the spin label at position 235 does not change upon inhibitor binding. This study suggests that the hairpin loop in NDM-1 moves over the metal ion during the catalysis and then moves back to its original position after hydrolysis, which is consistent with a previous hypothesis based on NMR solution studies on a related metallo-β-lactamase. This study also demonstrates that this loop motion occurs in the millisecond time domain.
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Affiliation(s)
- Mahesh Aitha
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, OH 45056, USA
| | - Abraham J Moller
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, OH 45056, USA
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, OH 45056, USA
| | - Masaki Horitani
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
| | - David L Tierney
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, OH 45056, USA
| | - Michael W Crowder
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, OH 45056, USA.
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Joseph B, Sikora A, Cafiso DS. Ligand Induced Conformational Changes of a Membrane Transporter in E. coli Cells Observed with DEER/PELDOR. J Am Chem Soc 2016; 138:1844-7. [PMID: 26795032 PMCID: PMC4837646 DOI: 10.1021/jacs.5b13382] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An unrealized goal in structural biology is the determination of structure and conformational change at high resolution for membrane proteins within the cellular environment. Pulsed electron-electron double resonance (PELDOR) is a well-established technique to follow conformational changes in purified membrane protein complexes. Here we demonstrate the first proof of concept for the use of PELDOR to observe conformational changes in a membrane protein in intact cells. We exploit the fact that outer membrane proteins usually lack reactive cysteines and that paramagnetic spin labels entering the periplasm are selectively reduced to achieve specific labeling of the cobalamin transporter BtuB in Escherichia coli. We characterize conformational changes in the second extracellular loop of BtuB upon ligand binding and compare the PELDOR data with high-resolution crystal structures. Our approach avoids detergent extraction, purification, and reconstitution usually required for these systems. With this approach, structure, function, conformational changes, and molecular interactions of outer membrane proteins can be studied at high resolution in the cellular environment.
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Affiliation(s)
- Benesh Joseph
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Arthur Sikora
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
| | - David S. Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
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Peraro MD, van der Goot FG. Pore-forming toxins: ancient, but never really out of fashion. Nat Rev Microbiol 2015; 14:77-92. [DOI: 10.1038/nrmicro.2015.3] [Citation(s) in RCA: 476] [Impact Index Per Article: 52.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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35
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Cosentino K, Ros U, García-Sáez AJ. Assembling the puzzle: Oligomerization of α-pore forming proteins in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:457-466. [PMID: 26375417 DOI: 10.1016/j.bbamem.2015.09.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/09/2015] [Indexed: 12/21/2022]
Abstract
Pore forming proteins (PFPs) share the ability of creating pores that allow the passage of ions, proteins or other constituents through a wide variety of target membranes, ranging from bacteria to humans. They often cause cell death, as pore formation disrupts the membrane permeability barrier required for maintaining cell homeostasis. The organization into supramolecular complexes or oligomers that pierce the membrane is a common feature of PFPs. However, the molecular pathway of self-assembly and pore opening remains unclear. Here, we review the most recent discoveries in the mechanism of membrane oligomerization and pore formation of a subset of PFPs, the α-PFPs, whose pore-forming domains are formed by helical segments. Only now we are starting to grasp the molecular details of their function, mainly thanks to the introduction of single molecule microscopy and nanoscopy techniques. This article is part of a Special Issue entitled: Pore-forming toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- Katia Cosentino
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Uris Ros
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany.,Center for Protein Studies, Havana University, Havana, Cuba
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
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