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He H, Wu C, Saqib M, Hao R. Single-molecule fluorescence methods for protein biomarker analysis. Anal Bioanal Chem 2023:10.1007/s00216-022-04502-9. [PMID: 36609860 DOI: 10.1007/s00216-022-04502-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/07/2022] [Accepted: 12/20/2022] [Indexed: 01/09/2023]
Abstract
Proteins have been considered key building blocks of life. In particular, the protein content of an organism and a cell offers significant information for the in-depth understanding of the disease and biological processes. Single-molecule protein detection/sequencing tools will revolutionize clinical (proteomics) research, offering ultrasensitivity for low-abundance biomarker (protein) detection, which is important for the realization of early-stage disease diagnosis and single-cell proteomics. This improved detection/measurement capability delivers new sets of techniques to explore new frontiers and address important challenges in various interdisciplinary areas including nanostructured materials, molecular medicine, molecular biology, and chemistry. Importantly, fluorescence-based methods have emerged as indispensable tools for single protein detection/sequencing studies, providing a higher signal-to-noise ratio (SNR). Improvements in fluorescent dyes/probes and detector capabilities coupled with advanced (image) analysis strategies have fueled current developments for single protein biomarker detections. For example, in comparison to conventional ELISA (i.e., based on ensembled measurements), single-molecule fluorescence detection is more sensitive, faster, and more accurate with reduced background, high-throughput, and so on. In comparison to MS sequencing, fluorescence-based single-molecule protein sequencing can achieve the sequencing of peptides themselves with higher sensitivity. This review summarizes various typical single-molecule detection technologies including their methodology (modes of operation), detection limits, advantages and drawbacks, and current challenges with recent examples. We describe the fluorescence-based single-molecule protein sequencing/detection based on five kinds of technologies such as fluorosequencing, N-terminal amino acid binder, nanopore light sensing, and DNA nanotechnology. Finally, we present our perspective for developing high-performance fluorescence-based sequencing/detection techniques.
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Affiliation(s)
- Haihan He
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China.,Research Center for Chemical Biology and Omics Analysis, School of Science, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Chuhong Wu
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China.,Research Center for Chemical Biology and Omics Analysis, School of Science, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Muhammad Saqib
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China.,Research Center for Chemical Biology and Omics Analysis, School of Science, Southern University of Science and Technology, Shenzhen, 518055, China.,Institute of Chemistry, Khwaja Fareed University of Engineering & Information Technology, Rahim Yar Khan 64200, Pakistan
| | - Rui Hao
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055, China. .,Research Center for Chemical Biology and Omics Analysis, School of Science, Southern University of Science and Technology, Shenzhen, 518055, China.
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2
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Novo M, Pérez-González C, Freire S, Al-Soufi W. Early Aggregation of Amyloid-β(1-42) Studied by Fluorescence Correlation Spectroscopy. Methods Mol Biol 2023; 2551:1-14. [PMID: 36310192 DOI: 10.1007/978-1-0716-2597-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease affecting cognitive and memory abilities and is believed to be linked to the formation and accumulation of neurotoxic aggregates of the Amyloid-β peptide (Aβ). In particular, it is the formation of soluble pre-fibrillar oligomers within the early stage of Aβ aggregation which is thought to represent a key step in the development of AD, thus underlining the interest in characterizing the aggregation process and the nature of these aggregates. In this context, fluorescence correlation spectroscopy (FCS) has emerged as a valuable alternative for the study of these systems in solution. Indeed, the use of FCS to study terminally labelled Aβ provides a means to detect changes in the size and concentration of initially monomeric Aβ samples by monitoring these fluorescently labelled species freely diffusing in solution with single-molecule resolution. Herein, we show how to employ FCS to study the early aggregation process of Aβ(1-42) and how this can be used to estimate the critical concentration for oligomer formation and to characterize the aggregates formed.
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Affiliation(s)
- Mercedes Novo
- Department of Physical Chemistry, Faculty of Science, University of Santiago de Compostela, Lugo, Spain.
| | - Cibrán Pérez-González
- Department of Physical Chemistry, Faculty of Science, University of Santiago de Compostela, Lugo, Spain
| | - Sonia Freire
- Department of Physical Chemistry, Faculty of Science, University of Santiago de Compostela, Lugo, Spain
| | - Wajih Al-Soufi
- Department of Physical Chemistry, Faculty of Science, University of Santiago de Compostela, Lugo, Spain
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3
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Lemmens V, Thevelein B, Vella Y, Kankowski S, Leonhard J, Mizuno H, Rocha S, Brône B, Meier JC, Hendrix J. Hetero-pentamerization determines mobility and conductance of Glycine receptor α3 splice variants. Cell Mol Life Sci 2022; 79:540. [PMID: 36197517 DOI: 10.1007/s00018-022-04506-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/21/2022] [Accepted: 07/23/2022] [Indexed: 11/05/2022]
Abstract
Glycine receptors (GlyRs) are ligand-gated pentameric chloride channels in the central nervous system. GlyR-α3 is a possible target for chronic pain treatment and temporal lobe epilepsy. Alternative splicing into K or L variants determines the subcellular fate and function of GlyR-α3, yet it remains to be shown whether its different splice variants can functionally co-assemble, and what the properties of such heteropentamers would be. Here, we subjected GlyR-α3 to a combined fluorescence microscopy and electrophysiology analysis. We employ masked Pearson’s and dual-color spatiotemporal correlation analysis to prove that GlyR-α3 splice variants heteropentamerize, adopting the mobility of the K variant. Fluorescence-based single-subunit counting experiments revealed a variable and concentration ratio dependent hetero-stoichiometry. Via cell-attached single-channel electrophysiology we show that heteropentamers exhibit currents in between those of K and L variants. Our data are compatible with a model where α3 heteropentamerization fine-tunes mobility and activity of GlyR-α3 channels, which is important to understand and tackle α3 related diseases.
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4
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Małecka EM, Hua B, Woodson SA. Single-Molecule FRET Studies of RNA Structural Rearrangements and RNA-RNA Interactions. Methods Mol Biol 2022; 2518:271-289. [PMID: 35666451 PMCID: PMC10052914 DOI: 10.1007/978-1-0716-2421-0_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
RNA-guided regulation of gene expression is found in all cell types. In this mode of regulation, antisense interactions between the regulatory RNA and its target are typically facilitated by a protein partner. Single-molecule fluorescence microscopy is a powerful tool for dissecting the conformational states and intermediates that contribute to target recognition. This chapter describes protocols for studying target recognition by bacterial small RNAs and their chaperone Hfq on the single-molecule level, using a total internal reflection fluorescence microscope. The sections cover the design of suitable RNA substrates for sRNA-mRNA annealing reactions, preparation of internally labeled mRNA for detecting conformational changes in the target, and key steps of the data analysis. These protocols can be adapted to other RNA-binding proteins that chaperone RNA interactions.
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Affiliation(s)
- Ewelina M Małecka
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA
| | - Boyang Hua
- Department of Molecular Biology and Genetics, Johns Hopkins Medical School, Baltimore, MD, USA
| | - Sarah A Woodson
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA.
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Yadav R, Senanayake KB, Comstock MJ. High-Resolution Optical Tweezers Combined with Multicolor Single-Molecule Microscopy. Methods Mol Biol 2022; 2478:141-240. [PMID: 36063322 DOI: 10.1007/978-1-0716-2229-2_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present an instrument that combines high-resolution optical tweezers and multicolor confocal fluorescence spectroscopy. Biological macromolecules exhibit complex conformation and stoichiometry changes in coordination with their motion and activity. To further our understanding of the complex machinery of life, we need methods that can simultaneously probe more than one degree of freedom of single molecules and complexes. Fluorescence optical tweezers, or "fleezers," combine the capabilities of optical tweezers and single-molecule fluorescence microscopy into a single instrument. Here we present the latest generation of a high-resolution fleezers instrument integrated with multicolor fluorescence spectroscopy. The tweezers portion of the instrument can manipulate biological macromolecules with pN scale forces while measuring subnanometer distances. Simultaneous with tweezers measurements, the multicolor fluorescence capability allows the direct observation of multiple molecules or multiple degrees of freedom which allows, for example, the observation of multiple proteins simultaneously within a complex. The instrument incorporates three fluorescence excitation lasers, all sourced from a single-mode optical fiber allowing a reliable alignment scheme, that allows, for example, three independent fluorescent probes or fluorescence resonance energy transfer (FRET) measurements and also increases flexibility in the choice of fluorescent probes. To avoid photobleaching and improve tweezers stability, the instrument implements a timesharing (using a single trap laser to produce a pair of traps via rapid switching between two locations) and interlacing (turning the trapping beam off when the fluorescence excitation beams are on and vice versa) scheme using acousto-optic modulators (AOM) to rapidly and precisely modulate lasers. Our latest "random phase" trap AOM control method obliterates previous residual trap positioning and bead position measurement errors. Here we present the general design principles and detailed construction and testing protocols for the instrument.
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Affiliation(s)
- Rajeev Yadav
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA
| | - Kasun B Senanayake
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA
| | - Matthew J Comstock
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA.
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Sobhy MA, Tehseen M, Takahashi M, Bralić A, De Biasio A, Hamdan SM. Implementing fluorescence enhancement, quenching, and FRET for investigating flap endonuclease 1 enzymatic reaction at the single-molecule level. Comput Struct Biotechnol J 2021; 19:4456-4471. [PMID: 34471492 PMCID: PMC8385120 DOI: 10.1016/j.csbj.2021.07.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 07/23/2021] [Accepted: 07/25/2021] [Indexed: 11/24/2022] Open
Abstract
Flap endonuclease 1 (FEN1) is an important component of the intricate molecular machinery for DNA replication and repair. FEN1 is a structure-specific 5' nuclease that cleaves nascent single-stranded 5' flaps during the maturation of Okazaki fragments. Here, we review our research primarily applying single-molecule fluorescence to resolve important mechanistic aspects of human FEN1 enzymatic reaction. The methodology presented in this review is aimed as a guide for tackling other biomolecular enzymatic reactions by fluorescence enhancement, quenching, and FRET and their combinations. Using these methods, we followed in real-time the structures of the substrate and product and 5' flap cleavage during catalysis. We illustrate that FEN1 actively bends the substrate to verify its features and continues to mold it to induce a protein disorder-to-order transitioning that controls active site assembly. This mechanism suppresses off-target cleavage of non-cognate substrates and promotes their dissociation with an accuracy that was underestimated from bulk assays. We determined that product release in FEN1 after the 5' flap release occurs in two steps; a brief binding to the bent nicked-product followed by longer binding to the unbent nicked-product before dissociation. Based on our cryo-electron microscopy structure of the human lagging strand replicase bound to FEN1, we propose how this two-step product release mechanism may regulate the final steps during the maturation of Okazaki fragments.
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Affiliation(s)
- Mohamed A Sobhy
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Muhammad Tehseen
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Masateru Takahashi
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Amer Bralić
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Alfredo De Biasio
- Leicester Institute of Structural & Chemical Biology and Department of Molecular & Cell Biology, University of Leicester, Lancaster Rd, Leicester LE1 7HB, UK
| | - Samir M Hamdan
- Laboratory of DNA Replication and Recombination, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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7
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Rice LJ, Ecroyd H, van Oijen AM. Illuminating amyloid fibrils: Fluorescence-based single-molecule approaches. Comput Struct Biotechnol J 2021; 19:4711-4724. [PMID: 34504664 PMCID: PMC8405898 DOI: 10.1016/j.csbj.2021.08.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/11/2021] [Accepted: 08/12/2021] [Indexed: 12/15/2022] Open
Abstract
The aggregation of proteins into insoluble filamentous amyloid fibrils is a pathological hallmark of neurodegenerative diseases that include Parkinson's disease and Alzheimer's disease. Since the identification of amyloid fibrils and their association with disease, there has been much work to describe the process by which fibrils form and interact with other proteins. However, due to the dynamic nature of fibril formation and the transient and heterogeneous nature of the intermediates produced, it can be challenging to examine these processes using techniques that rely on traditional ensemble-based measurements. Single-molecule approaches overcome these limitations as rare and short-lived species within a population can be individually studied. Fluorescence-based single-molecule methods have proven to be particularly useful for the study of amyloid fibril formation. In this review, we discuss the use of different experimental single-molecule fluorescence microscopy approaches to study amyloid fibrils and their interaction with other proteins, in particular molecular chaperones. We highlight the mechanistic insights these single-molecule techniques have already provided in our understanding of how fibrils form, and comment on their potential future use in studying amyloid fibrils and their intermediates.
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Affiliation(s)
- Lauren J. Rice
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Illawarra Health & Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Heath Ecroyd
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Illawarra Health & Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Antoine M. van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Illawarra Health & Medical Research Institute, Wollongong, NSW 2522, Australia
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8
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Lim G, Hohng S. Single-molecule Fluorescence Technique to Monitor the Co-transcriptional Formation of G-quadruplex and R-loop Structures. Bio Protoc 2021; 11:e4069. [PMID: 34327266 DOI: 10.21769/bioprotoc.4069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 03/14/2021] [Accepted: 03/25/2021] [Indexed: 11/02/2022] Open
Abstract
G-quadruplexes (GQ) and R-loops are non-canonical nucleic acid structures related to gene regulation and genome instability that can be formed during transcription; however, their formation mechanisms remain elusive. To address this question, we developed a single-molecule fluorescence technique to monitor the formation of G-quadruplex and R-loop structures during transcription. Using this technique, we found that R-loop formation precedes GQ formation and that there exists a positive feedback loop between G-quadruplex and R-loop formation.
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Affiliation(s)
- Gunhyoung Lim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, Republic of Korea
| | - Sungchul Hohng
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, Republic of Korea
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9
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Parperis C, Wallace MI. Single-molecule imaging of pore-forming toxin dynamics in droplet interface bilayers. Methods Enzymol 2021; 649:431-459. [PMID: 33712195 DOI: 10.1016/bs.mie.2021.01.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Single-channel recording from pore-forming toxins (PFTs) provides a clear and direct molecular readout of toxin action. However to complete any mechanistic understanding of PFT behavior, this functional kinetic readout must be linked to the underlying changes in toxin structure, binding, conformation, or stoichiometry. Here we review how single-molecule imaging methods might be used to further our understanding of PFTs, and provide detailed practical guidance on the use of droplet interface bilayers as a method capable of examining both single-molecule fluorescence and single-channel electrical signals from PFTs.
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Affiliation(s)
- Christopher Parperis
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom
| | - Mark I Wallace
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom.
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10
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Mivelaz M, Fierz B. Observing protein interaction dynamics to chemically defined chromatin fibers by colocalization single-molecule fluorescence microscopy. Methods 2020; 184:112-124. [PMID: 32004546 DOI: 10.1016/j.ymeth.2020.01.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 01/15/2020] [Accepted: 01/26/2020] [Indexed: 02/04/2023] Open
Abstract
In eukaryotic cells, the genome is packaged into chromatin and exists in different states, ranging from open euchromatic regions to highly condensed heterochromatic regions. Chromatin states are highly dynamic and are organized by an interplay of histone post-translational modifications and effector proteins, both of which are central in the regulation of gene expression. For this, chromatin effector proteins must first search the nucleus for their targets, before binding and performing their role. A key question is how chromatin effector proteins search, interact with and alter the different chromatin environments. Here we present a modular fluorescence based in vitro workflow to directly observe dynamic interactions of effector proteins with defined chromatin fibres, replicating different chromatin states. We discuss the design and creation of chromatin assemblies, the synthesis of modified histones, the fabrication of microchannels and the approach to data acquisition and analysis. All of this with the aim to better understand the complex in vivo relationship between chromatin structure and gene expression.
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Affiliation(s)
- Maxime Mivelaz
- École Polytechnique Fédérale de Lausanne, SB ISIC LCBM, Station 6, CH-1015 Lausanne, Switzerland
| | - Beat Fierz
- École Polytechnique Fédérale de Lausanne, SB ISIC LCBM, Station 6, CH-1015 Lausanne, Switzerland.
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11
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Hon J, Lu Y. Single-molecule methods for measuring ubiquitination and protein stability. Methods Enzymol 2019; 619:225-47. [PMID: 30910022 DOI: 10.1016/bs.mie.2018.12.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2023]
Abstract
The ubiquitin-proteasome system (UPS) contributes to changes in cell state and homeostatic maintenance in humans by modulating the stability of about a third of human proteins. For example, cell-cycle regulation requires a central ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C), which starts a ubiquitination cascade leading to the degradation of multiple targets. This targeted degradation is mediated by the 26S proteasome, a 2.5-MDa protein complex, which recognizes and degrades ubiquitinated proteins at rates partially controlled by the variations in ubiquitin chain topology. Substrate selectivity of ubiquitin ligases such as the APC/C and of the 26S proteasome from pools of near-identical targets reflects highly regulated kinetic mechanisms. Single-molecule techniques are powerful tools that allow distinction between differential substrate affinities and identification of reaction intermediates in complex mixtures. Here we describe fluorescence-based single-molecule imaging of in vitro ubiquitination reactions catalyzed by the APC/C and ubiquitin-dependent degradation reactions catalyzed by the 26S proteasome.
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12
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Senavirathne G, Lopez MA, Messer R, Fishel R, Yoder KE. Expression and purification of nuclease-free protocatechuate 3,4-dioxygenase for prolonged single-molecule fluorescence imaging. Anal Biochem 2018; 556:78-84. [PMID: 29932890 PMCID: PMC6076860 DOI: 10.1016/j.ab.2018.06.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 05/23/2018] [Accepted: 06/16/2018] [Indexed: 10/28/2022]
Abstract
Single-molecule (SM) microscopy is a powerful tool capable of visualizing individual molecules and events in real time. SM imaging may rely on proteins or nucleic acids labelled with a fluorophore. Unfortunately photobleaching of fluorophores leads to irreversible loss of signal, impacting the collection of data from SM experiments. Trace amounts of dissolved oxygen (O2) are the main cause of photobleaching. Oxygen scavenging systems (OSS) have been developed that decrease dissolved O2. Commercial OSS enzyme preparations are frequently contaminated with nucleases that damage nucleic acid substrates. In this protocol, we purify highly active Pseudomonas putida protocatechuate 3,4-dioxygenase (PCD) without nuclease contaminations. Quantitation of Cy3 photostability revealed that PCD with its substrate protocatechuic acid (PCA) increased the fluorophore half-life 100-fold. This low cost purification method of recombinant PCD yields an enzyme superior to commercially available OSS that is effectively free of nuclease activity.
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Affiliation(s)
- Gayan Senavirathne
- Department of Cancer Biology and Genetics, The Ohio State University Medical Center, Columbus, OH 43210, USA
| | - Miguel A. Lopez
- Department of Cancer Biology and Genetics, The Ohio State University Medical Center, Columbus, OH 43210, USA
| | - Ryan Messer
- Department of Cancer Biology and Genetics, The Ohio State University Medical Center, Columbus, OH 43210, USA
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Medical Center, Columbus, OH, 43210, USA.
| | - Kristine E. Yoder
- Department of Cancer Biology and Genetics, The Ohio State University Medical Center, Columbus, OH 43210, USA,To whom correspondence should be addressed. Tel: (614) 688-2106; , Correspondence may also be addressed to. Tel: (614) 292-2484;
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Fareh M, Joo C. Probing RNA-Protein Interactions with Single-Molecule Pull-Down Assays. Methods Mol Biol 2018; 1814:267-285. [PMID: 29956238 DOI: 10.1007/978-1-4939-8591-3_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recent advances in single-molecule techniques allow for dynamic observations of the interactions between various protein assemblies and RNA molecules with high spatiotemporal resolution. However, it remains challenging to obtain functional eukaryotic protein complexes and cost-effective fluorescently labeled RNAs to study their interactions at the single-molecule level. Here, we describe protocols combining single-molecule fluorescence with various protein complex pull-down techniques to determine the function of RNA-interacting protein complexes of interest. We provide step-by-step guidance for using novel single-molecule techniques including RNA labeling, protein complexes purification, and single-molecule imaging. As a proof-of-concept of the utility of our single-molecule approaches, we show how human Dicer and its cofactor TRBP orchestrate the biogenesis of microRNA in real time. These single-molecule pull-down and fluorescence assays provide sub-second time resolution and can be applied to various ribonucleoprotein complexes that are essential for cellular processes.
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Affiliation(s)
- Mohamed Fareh
- Department of BioNanoScience, Kavli Institute of NanoScience, Delft University of Technology, Building 58, vander Maasweg 9, Delft, 2629 HZ, The Netherlands.
- Cancer Immunology Program, Peter MacCallum Cancer Center, East Melbourne, Victoria,Australia. Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.
| | - Chirlmin Joo
- Department of BioNanoScience, Kavli Institute of NanoScience, Delft University of Technology, Building 58, vander Maasweg 9, Delft, 2629 HZ, The Netherlands
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Abstract
Nucleosomes are the fundamental organizing unit of all eukaryotic genomes. Understanding how proteins gain access to DNA-binding sites located within nucleosomes is important for understanding DNA processing including transcription, replication, and repair. Single-molecule total internal reflection fluorescence (smTIRF) microscopy measurements can provide key insight into how proteins gain and maintain access to DNA sites within nucleosomes. Here, we describe methods for smTIRF experiments including the preparation of fluorophore-labeled nucleosomes, the smTIRF system, data acquisition, analysis, and controls. These methods are presented for investigating transcription factor binding within nucleosomes. However, they are applicable for investigating the binding of any site-specific DNA-binding protein within nucleosomes.
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Affiliation(s)
- M D Gibson
- The Ohio State University, Columbus, OH, United States
| | - M Brehove
- The Ohio State University, Columbus, OH, United States
| | - Y Luo
- The Ohio State University, Columbus, OH, United States
| | - J North
- The Ohio State University, Columbus, OH, United States
| | - M G Poirier
- The Ohio State University, Columbus, OH, United States.
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15
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Goudsmits JMH, van Oijen AM, Slotboom DJ. Single-Molecule Fluorescence Studies of Membrane Transporters Using Total Internal Reflection Microscopy. Methods Enzymol 2017; 594:101-121. [PMID: 28779837 DOI: 10.1016/bs.mie.2017.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Cells are delineated by a lipid bilayer that physically separates the inside from the outer environment. Most polar, charged, or large molecules require proteins to reduce the energetic barrier for passage across the membrane and to achieve transport rates that are relevant for life. Here, we describe techniques to visualize the functioning of membrane transport proteins with fluorescent probes at the single-molecule level. First, we explain how to produce membrane-reconstituted transporters with fluorescent labels. Next, we detail the construction of a microfluidic flow cell to image immobilized proteoliposomes on a total internal reflection fluorescence microscope. We conclude by describing the methods that are needed to analyze fluorescence movies and obtain useful single-molecule data.
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16
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Iljina M, Hong L, Horrocks MH, Ludtmann MH, Choi ML, Hughes CD, Ruggeri FS, Guilliams T, Buell AK, Lee JE, Gandhi S, Lee SF, Bryant CE, Vendruscolo M, Knowles TPJ, Dobson CM, De Genst E, Klenerman D. Nanobodies raised against monomeric ɑ-synuclein inhibit fibril formation and destabilize toxic oligomeric species. BMC Biol 2017; 15:57. [PMID: 28673288 PMCID: PMC5496350 DOI: 10.1186/s12915-017-0390-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/06/2017] [Indexed: 11/16/2022] Open
Abstract
Background The aggregation of the protein ɑ-synuclein (ɑS) underlies a range of increasingly common neurodegenerative disorders including Parkinson’s disease. One widely explored therapeutic strategy for these conditions is the use of antibodies to target aggregated ɑS, although a detailed molecular-level mechanism of the action of such species remains elusive. Here, we characterize ɑS aggregation in vitro in the presence of two ɑS-specific single-domain antibodies (nanobodies), NbSyn2 and NbSyn87, which bind to the highly accessible C-terminal region of ɑS. Results We show that both nanobodies inhibit the formation of ɑS fibrils. Furthermore, using single-molecule fluorescence techniques, we demonstrate that nanobody binding promotes a rapid conformational conversion from more stable oligomers to less stable oligomers of ɑS, leading to a dramatic reduction in oligomer-induced cellular toxicity. Conclusions The results indicate a novel mechanism by which diseases associated with protein aggregation can be inhibited, and suggest that NbSyn2 and NbSyn87 could have significant therapeutic potential. Electronic supplementary material The online version of this article (doi:10.1186/s12915-017-0390-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Marija Iljina
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Liu Hong
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.,Zhou Pei-Yuan Center for Applied Mathematics, Tsinghua University, Beijing, 100084, China
| | - Mathew H Horrocks
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.,Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Marthe H Ludtmann
- Department of Molecular Neuroscience, University College London, Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Minee L Choi
- Department of Molecular Neuroscience, University College London, Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Craig D Hughes
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 0ES, UK
| | - Francesco S Ruggeri
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Tim Guilliams
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.,Present address: Healx Ltd., St John's Innovation Centre, Cowley Road, Cambridge, CB4 0WS, UK
| | - Alexander K Buell
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.,Present address: Institute of Physical Biology, University of Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Ji-Eun Lee
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Sonia Gandhi
- Department of Molecular Neuroscience, University College London, Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Steven F Lee
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Clare E Bryant
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 0ES, UK
| | - Michele Vendruscolo
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Tuomas P J Knowles
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Christopher M Dobson
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
| | - Erwin De Genst
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK. .,Present address: Astra Zeneca, Innovative Medicines Discovery Sciences Unit 310, Darwin Building, Cambridge Science Park, Milton Road, Cambridge, CB4 0WG, UK.
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
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17
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LeBlanc S, Wilkins H, Li Z, Kaur P, Wang H, Erie DA. Using Atomic Force Microscopy to Characterize the Conformational Properties of Proteins and Protein-DNA Complexes That Carry Out DNA Repair. Methods Enzymol 2017; 592:187-212. [PMID: 28668121 PMCID: PMC5761736 DOI: 10.1016/bs.mie.2017.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Atomic force microscopy (AFM) is a scanning probe technique that allows visualization of single biomolecules and complexes deposited on a surface with nanometer resolution. AFM is a powerful tool for characterizing protein-protein and protein-DNA interactions. It can be used to capture snapshots of protein-DNA solution dynamics, which in turn, enables the characterization of the conformational properties of transient protein-protein and protein-DNA interactions. With AFM, it is possible to determine the stoichiometries and binding affinities of protein-protein and protein-DNA associations, the specificity of proteins binding to specific sites on DNA, and the conformations of the complexes. We describe methods to prepare and deposit samples, including surface treatments for optimal depositions, and how to quantitatively analyze images. We also discuss a new electrostatic force imaging technique called DREEM, which allows the visualization of the path of DNA within proteins in protein-DNA complexes. Collectively, these methods facilitate the development of comprehensive models of DNA repair and provide a broader understanding of all protein-protein and protein-nucleic acid interactions. The structural details gleaned from analysis of AFM images coupled with biochemistry provide vital information toward establishing the structure-function relationships that govern DNA repair processes.
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Affiliation(s)
- Sharonda LeBlanc
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Hunter Wilkins
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Zimeng Li
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Parminder Kaur
- North Carolina State University, Raleigh, NC, United States
| | - Hong Wang
- North Carolina State University, Raleigh, NC, United States
| | - Dorothy A Erie
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
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18
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Abstract
Non-homologous end joining (NHEJ) repairs the majority of DNA double-strand breaks in human cells, yet the detailed order of events in this process has remained obscure. Here, we describe how to employ Xenopus laevis egg extract for the study of NHEJ. The egg extract is easy to prepare in large quantities, and it performs efficient end joining that requires the core end joining proteins Ku, DNA-PKcs, XLF, XRCC4, and DNA ligase IV. These factors, along with the rest of the soluble proteome, are present at endogenous concentrations, allowing mechanistic analysis in a system that begins to approximate the complexity of cellular end joining. We describe an ensemble assay that monitors covalent joining of DNA ends and fluorescence assays that detect joining of single pairs of DNA ends. The latter assay discerns at least two discrete intermediates in the bridging of DNA ends.
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Affiliation(s)
| | - Johannes C Walter
- Harvard Medical School, Boston, MA, United States; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, United States.
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19
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Naz A, Cui Y, Collins CJ, Thompson DH, Irudayaraj J. PLGA-PEG nano-delivery system for epigenetic therapy. Biomed Pharmacother 2017; 90:586-597. [PMID: 28407579 DOI: 10.1016/j.biopha.2017.03.093] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 03/22/2017] [Accepted: 03/27/2017] [Indexed: 12/31/2022] Open
Abstract
Efficient delivery of cytidine analogues such as Azacitidine (AZA) into solid tumors constitutes a primary challenge in epigenetic therapies. We developed a di-block nano-vector based on poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) for stabilization of the conjugated AZA under physiological conditions. With equimolar drug content, our nano-conjugate could elicit a better anti-proliferative effect over free drug in breast cancer both in vitro and in vivo, through reactivation of p21 and BRCA1 to restrict cell proliferation. In addition, we applied single-molecule fluorescence tools to characterize the intracellular behavior of the AZA-PLGE-PEG nano-micelles at a finer spatiotemporal resolution. Our results suggest that the nano-micelles could effectively enrich in cancer cells and may not be limited by nucleoside transporters. Afterwards, the internalized nano-micelles exhibit pH-dependent release and resistance to active efflux. Altogether, our work describes a delivery strategy for DNA demethylating agents with nanoscale tunability, providing a cost-effective option for pharmaceutics.
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Affiliation(s)
- Asia Naz
- Bindley Bioscience Center and Purdue Center for Cancer Research, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA; Department of Pharmaceutical Chemistry, University of Karachi, Karachi 75270, Pakistan
| | - Yi Cui
- Bindley Bioscience Center and Purdue Center for Cancer Research, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | | | - David H Thompson
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Joseph Irudayaraj
- Bindley Bioscience Center and Purdue Center for Cancer Research, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA.
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20
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Abstract
We describe the design, construction, and application of an instrument combining dual-trap, high-resolution optical tweezers and a confocal microscope. This hybrid instrument allows nanomechanical manipulation and measurement simultaneously with single-molecule fluorescence detection. We present the general design principles that overcome the challenges of maximizing optical trap resolution while maintaining single-molecule fluorescence sensitivity, and provide details on the construction and alignment of the instrument. This powerful new tool is just beginning to be applied to biological problems. We present step-by-step instructions on an application of this technique that highlights the instrument's capabilities, detecting conformational dynamics in a nucleic acid-processing enzyme.
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Affiliation(s)
- K.D. Whitley
- University of Illinois at Urbana–Champaign, Urbana, IL, United States
| | - M.J. Comstock
- Michigan State University, East Lansing, MI, United States
| | - Y.R. Chemla
- University of Illinois at Urbana–Champaign, Urbana, IL, United States,Center for the Physics of Living Cells, University of Illinois at Urbana–Champaign, Urbana, IL, United States,Corresponding author:
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21
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Whitley KD, Comstock MJ, Chemla YR. High-Resolution "Fleezers": Dual-Trap Optical Tweezers Combined with Single-Molecule Fluorescence Detection. Methods Mol Biol 2017; 1486:183-256. [PMID: 27844430 DOI: 10.1007/978-1-4939-6421-5_8] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Recent advances in optical tweezers have greatly expanded their measurement capabilities. A new generation of hybrid instrument that combines nanomechanical manipulation with fluorescence detection-fluorescence optical tweezers, or "fleezers"-is providing a powerful approach to study complex macromolecular dynamics. Here, we describe a combined high-resolution optical trap/confocal fluorescence microscope that can simultaneously detect sub-nanometer displacements, sub-piconewton forces, and single-molecule fluorescence signals. The primary technical challenge to these hybrid instruments is how to combine both measurement modalities without sacrificing the sensitivity of either one. We present general design principles to overcome this challenge and provide detailed, step-by-step instructions to implement them in the construction and alignment of the instrument. Lastly, we present a set of protocols to perform a simple, proof-of-principle experiment that highlights the instrument capabilities.
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22
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Lamichhane R, Liu JJ, Pauszek RF, Millar DP. Fluorophore Labeling, Nanodisc Reconstitution and Single-molecule Observation of a G Protein-coupled Receptor. Bio Protoc 2017; 7:e2332. [PMID: 29170748 DOI: 10.21769/bioprotoc.2332] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Activation of G protein-coupled receptors (GPCRs) by agonist ligands is mediated by a transition from an inactive to active receptor conformation. We describe a novel single-molecule assay that monitors activation-linked conformational transitions in individual GPCR molecules in real-time. The receptor is site-specifically labeled with a Cy3 fluorescence probe at the end of trans-membrane helix 6 and reconstituted in phospholipid nanodiscs tethered to a microscope slide. Individual receptor molecules are then monitored over time by single-molecule total internal reflection fluorescence microscopy, revealing spontaneous transitions between inactive and active-like conformations. The assay provides information on the equilibrium distribution of inactive and active receptor conformations and the rate constants for conformational exchange. The experiments can be performed in the absence of ligands, revealing the spontaneous conformational transitions responsible for basal signaling activity, or in the presence of agonist or inverse agonist ligands, revealing how the ligands alter the dynamics of the receptor to either stimulate or repress signaling activity. The resulting mechanistic information is useful for the design of improved GPCR-targeting drugs. The single-molecule assay is described in the context of the β2 adrenergic receptor, but can be extended to a variety of GPCRs.
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Affiliation(s)
- Rajan Lamichhane
- Department of Integrative Structural & Computational Biology, the Scripps Research Institute, La Jolla, CA, USA
| | - Jeffrey J Liu
- Department of Integrative Structural & Computational Biology, the Scripps Research Institute, La Jolla, CA, USA.,Max Planck Institute for Biochemistry, Martinsried, Germany
| | - Raymond F Pauszek
- Department of Integrative Structural & Computational Biology, the Scripps Research Institute, La Jolla, CA, USA
| | - David P Millar
- Department of Integrative Structural & Computational Biology, the Scripps Research Institute, La Jolla, CA, USA
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23
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Duboc C, Fan J, Graves ET, Strick TR. Preparation of DNA Substrates and Functionalized Glass Surfaces for Correlative Nanomanipulation and Colocalization (NanoCOSM) of Single Molecules. Methods Enzymol 2016; 582:275-296. [PMID: 28062038 DOI: 10.1016/bs.mie.2016.09.048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Simultaneous nanomanipulation and colocalization of single molecules (NanoCOSM) provides a unique opportunity to correlate the mechanical properties and activities of biomolecules with their conformational states or states of assembly as part of dynamic macromolecular complexes. This opens the door to real-time single-molecule analysis of the correlations between structure, function, and composition of large multicomponent protein complexes.
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Affiliation(s)
- C Duboc
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France
| | - J Fan
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France
| | - E T Graves
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France
| | - T R Strick
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France; Ecole Normale Supérieure, Institut de Biologie de l'ENS (iBENS), INSERM, CNRS, PSL Research University, Paris, France.
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24
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Abstract
Structure and dynamics of DNA impact how the genetic code is processed and maintained. In addition to its biological importance, DNA has been utilized as building blocks of various nanomachines and nanostructures. Thus, understanding the physical properties of DNA is of fundamental importance to basic sciences and engineering applications. DNA can undergo various physical changes. Among them, DNA looping is unique in that it can bring two distal sites together, and thus can be used to mediate interactions over long distances. In this paper, we introduce a FRET-based experimental tool to study DNA looping at the single molecule level. We explain the connection between experimental measurables and a theoretical concept known as the J factor with the intent of raising awareness of subtle theoretical details that should be considered when drawing conclusions. We also explore DNA looping-assisted protein diffusion mechanism called intersegmental transfer using protein induced fluorescence enhancement (PIFE). We present some preliminary results and future outlooks.
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Affiliation(s)
- Jiyoun Jeong
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
| | - Tung T Le
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
| | - Harold D Kim
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
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25
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Duboc C, Graves ET, Strick TR. Simple calibration of TIR field depth using the supercoiling response of DNA. Methods 2016; 105:56-61. [PMID: 27038746 DOI: 10.1016/j.ymeth.2016.03.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 03/29/2016] [Indexed: 11/29/2022] Open
Abstract
The combination of single-molecule fluorescence and nanomanipulation techniques into a single experimental platform enables one to carry out correlative analysis of the composition and the activity of complex, multicomponent molecular systems. Here we describe implementation and calibration of such a combined system allowing simultaneous single-molecule force spectroscopy and fluorescence imaging of proteins acting on the DNA using magnetic trapping coupled with fluorescence excitation based on a Total Internal Reflection (TIR), or evanescent, field. We propose a simple and robust in situ method for calibration of the TIR field depth against the mechanical properties of nanomanipulated DNA, and which is made possible by the fact that the magnetic bead used to trap and nanomanipulate DNA and measure its conformation also exhibits autofluorescence in the TIR field. Indeed, the fact that the bead size is on the 1-micron scale does not preclude sensitive probing of an intensity field which decays exponentially on the 0.1micron-scale. We demonstrate the usefulness of this approach by mapping out TIR field depth as a function of the angle of incidence of the illuminating laser at the glass-water interface and showing that one recovers the expected theoretical relationship between field depth and angle of incidence.
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Affiliation(s)
- Camille Duboc
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France
| | - Evan T Graves
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France
| | - Terence R Strick
- Institut Jacques Monod, Centre National de la Recherche Scientifique, University of Paris Diderot and Sorbonne Paris Cité, Paris, France; Ecole Normale Supérieure, Institut de Biologie de l'ENS (iBENS), INSERM, CNRS, PSL Research University, Paris, France.
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26
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Fareh M, Loeff L, Szczepaniak M, Haagsma AC, Yeom KH, Joo C. Single-molecule pull-down for investigating protein-nucleic acid interactions. Methods 2016; 105:99-108. [PMID: 27017911 DOI: 10.1016/j.ymeth.2016.03.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/26/2016] [Accepted: 03/24/2016] [Indexed: 12/30/2022] Open
Abstract
The genome and transcriptome are constantly modified by proteins in the cell. Recent advances in single-molecule techniques allow for high spatial and temporal observations of these interactions between proteins and nucleic acids. However, due to the difficulty of obtaining functional protein complexes, it remains challenging to study the interactions between macromolecular protein complexes and nucleic acids. Here, we combined single-molecule fluorescence with various protein complex pull-down techniques to determine the function and stoichiometry of ribonucleoprotein complexes. Through the use of three examples of protein complexes from eukaryotic cells (Drosha, Dicer, and TUT4 protein complexes), we provide step-by-step guidance for using novel single-molecule techniques. Our single-molecule methods provide sub-second and nanometer resolution and can be applied to other nucleoprotein complexes that are essential for cellular processes.
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Affiliation(s)
- Mohamed Fareh
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands
| | - Luuk Loeff
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands
| | - Malwina Szczepaniak
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands
| | - Anna C Haagsma
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands
| | - Kyu-Hyeon Yeom
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands
| | - Chirlmin Joo
- Kavli Institute of NanoScience and Department of BioNanoScience, Delft University of Technology, Delft 2629HZ, The Netherlands.
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27
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Boehm EM, Subramanyam S, Ghoneim M, Washington MT, Spies M. Quantifying the Assembly of Multicomponent Molecular Machines by Single-Molecule Total Internal Reflection Fluorescence Microscopy. Methods Enzymol 2016; 581:105-45. [PMID: 27793278 DOI: 10.1016/bs.mie.2016.08.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Large, dynamic macromolecular complexes play essential roles in many cellular processes. Knowing how the components of these complexes associate with one another and undergo structural rearrangements is critical to understanding how they function. Single-molecule total internal reflection fluorescence (TIRF) microscopy is a powerful approach for addressing these fundamental issues. In this article, we first discuss single-molecule TIRF microscopes and strategies to immobilize and fluorescently label macromolecules. We then review the use of single-molecule TIRF microscopy to study the formation of binary macromolecular complexes using one-color imaging and inhibitors. We conclude with a discussion of the use of TIRF microscopy to examine the formation of higher-order (i.e., ternary) complexes using multicolor setups. The focus throughout this article is on experimental design, controls, data acquisition, and data analysis. We hope that single-molecule TIRF microscopy, which has largely been the province of specialists, will soon become as common in the tool box of biophysicists and biochemists as structural approaches have become today.
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28
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Gauer J, LeBlanc S, Hao P, Qiu R, Case B, Sakato M, Hingorani M, Erie D, Weninger K. Single-Molecule FRET to Measure Conformational Dynamics of DNA Mismatch Repair Proteins. Methods Enzymol 2016; 581:285-315. [PMID: 27793283 PMCID: PMC5423442 DOI: 10.1016/bs.mie.2016.08.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Single-molecule FRET measurements have a unique sensitivity to protein conformational dynamics. The FRET signals can either be interpreted quantitatively to provide estimates of absolute distance in a molecule configuration or can be qualitatively interpreted as distinct states, from which quantitative kinetic schemes for conformational transitions can be deduced. Here we describe methods utilizing single-molecule FRET to reveal the conformational dynamics of the proteins responsible for DNA mismatch repair. Experimental details about the proteins, DNA substrates, fluorescent labeling, and data analysis are included. The complementarity of single molecule and ensemble kinetic methods is discussed as well.
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Affiliation(s)
- J.W. Gauer
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - S. LeBlanc
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - P. Hao
- North Carolina State University, Raleigh, NC, United States
| | - R. Qiu
- North Carolina State University, Raleigh, NC, United States
| | - B.C. Case
- Wesleyan University, Middletown, CT, United States
| | - M. Sakato
- Wesleyan University, Middletown, CT, United States
| | | | - D.A. Erie
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States,Corresponding authors: ;
| | - K.R. Weninger
- North Carolina State University, Raleigh, NC, United States,Corresponding authors: ;
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29
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Arnett DC, Persechini A, Tran QK, Black DJ, Johnson CK. Fluorescence quenching studies of structure and dynamics in calmodulin-eNOS complexes. FEBS Lett 2015; 589:1173-8. [PMID: 25871521 DOI: 10.1016/j.febslet.2015.03.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/17/2015] [Accepted: 03/31/2015] [Indexed: 10/23/2022]
Abstract
Activation of endothelial nitric oxide synthase (eNOS) by calmodulin (CaM) facilitates formation of a sequence of conformational states that is not well understood. Fluorescence decays of fluorescently labeled CaM bound to eNOS reveal four distinct conformational states and single-molecule fluorescence trajectories show multiple fluorescence states with transitions between states occurring on time scales of milliseconds to seconds. A model is proposed relating fluorescence quenching states to enzyme conformations. Specifically, we propose that the most highly quenched state corresponds to CaM docked to an oxygenase domain of the enzyme. In single-molecule trajectories, this state occurs with time lags consistent with the oxygenase activity of the enzyme.
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Affiliation(s)
- David C Arnett
- Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA; Department of Chemistry, Northwestern College, Orange City, IA 51041, USA
| | - Anthony Persechini
- Division of Molecular Biology and Biochemistry and Division of Cell Biology and Biophysics, University of Missouri at Kansas City, Kansas City, MO 64410, USA
| | - Quang-Kim Tran
- Division of Molecular Biology and Biochemistry and Division of Cell Biology and Biophysics, University of Missouri at Kansas City, Kansas City, MO 64410, USA
| | - D J Black
- Division of Molecular Biology and Biochemistry and Division of Cell Biology and Biophysics, University of Missouri at Kansas City, Kansas City, MO 64410, USA
| | - Carey K Johnson
- Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA.
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30
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Abstract
Luminescence blinking is an inherent feature of optical emission from individual fluorescent molecules and quantum dots. There have been intense efforts, although not with complete resolution, toward the understanding of the mechanistic origin of blinking and also its mitigation in quantum dots. As an advance in our microscopic view of blinking, we show that the luminescence blinking of a quantum dot becomes unusually heavy in the temporal vicinity of a reactive transformation. This stage of heavy blinking is a result of defects/dopants formed within the quantum dot on its path to conversion. The evolution of blinking behavior along the reaction path allows us to measure the lifetime of the critical dopant-related intermediate in the reaction. This work establishes luminescence blinking as a single-nanocrystal level probe of catalytic, photocatalytic, and electrochemical events occurring in the solid-state or on semiconductor surfaces.
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Affiliation(s)
- Aaron L Routzahn
- †Department of Chemistry, ‡Department of Physics, and §Materials Research Lab, University of Illinois, Urbana-Champaign, Illinois 61801, United States
| | - Prashant K Jain
- †Department of Chemistry, ‡Department of Physics, and §Materials Research Lab, University of Illinois, Urbana-Champaign, Illinois 61801, United States
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Stracy M, Uphoff S, Garza de Leon F, Kapanidis AN. In vivo single-molecule imaging of bacterial DNA replication, transcription, and repair. FEBS Lett 2014; 588:3585-94. [PMID: 24859634 DOI: 10.1016/j.febslet.2014.05.026] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 05/12/2014] [Accepted: 05/14/2014] [Indexed: 11/25/2022]
Abstract
In vivo single-molecule experiments offer new perspectives on the behaviour of DNA binding proteins, from the molecular level to the length scale of whole bacterial cells. With technological advances in instrumentation and data analysis, fluorescence microscopy can detect single molecules in live cells, opening the doors to directly follow individual proteins binding to DNA in real time. In this review, we describe key technical considerations for implementing in vivo single-molecule fluorescence microscopy. We discuss how single-molecule tracking and quantitative super-resolution microscopy can be adapted to extract DNA binding kinetics, spatial distributions, and copy numbers of proteins, as well as stoichiometries of protein complexes. We highlight experiments which have exploited these techniques to answer important questions in the field of bacterial gene regulation and transcription, as well as chromosome replication, organisation and repair. Together, these studies demonstrate how single-molecule imaging is transforming our understanding of DNA-binding proteins in cells.
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Affiliation(s)
- Mathew Stracy
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Stephan Uphoff
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; Department of Systems Biology, Harvard Medical School, Boston, MA 02138, USA
| | - Federico Garza de Leon
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
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Abstract
DNA mismatch repair, which involves is a widely conserved set of proteins, is essential to limit genetic drift in all organisms. The same system of proteins plays key roles in many cancer related cellular transactions in humans. Although the basic process has been reconstituted in vitro using purified components, many fundamental aspects of DNA mismatch repair remain hidden due in part to the complexity and transient nature of the interactions between the mismatch repair proteins and DNA substrates. Single molecule methods offer the capability to uncover these transient but complex interactions and allow novel insights into mechanisms that underlie DNA mismatch repair. In this review, we discuss applications of single molecule methodology including electron microscopy, atomic force microscopy, particle tracking, FRET, and optical trapping to studies of DNA mismatch repair. These studies have led to formulation of mechanistic models of how proteins identify single base mismatches in the vast background of matched DNA and signal for their repair.
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Affiliation(s)
- Dorothy A Erie
- Department of Chemistry and Curriculum in Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States.
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, United States
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Uphoff S, Kapanidis AN. Studying the organization of DNA repair by single-cell and single-molecule imaging. DNA Repair (Amst) 2014; 20:32-40. [PMID: 24629485 PMCID: PMC4119245 DOI: 10.1016/j.dnarep.2014.02.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 02/09/2014] [Accepted: 02/14/2014] [Indexed: 12/26/2022]
Abstract
Single-cell experiments to study stochastic events and heterogeneity in DNA repair. Quantifying DNA repair protein concentration, diffusion, and localization in cells. Direct observation of DNA repair using photoactivated single-molecule tracking.
DNA repair safeguards the genome against a diversity of DNA damaging agents. Although the mechanisms of many repair proteins have been examined separately in vitro, far less is known about the coordinated function of the whole repair machinery in vivo. Furthermore, single-cell studies indicate that DNA damage responses generate substantial variation in repair activities across cells. This review focuses on fluorescence imaging methods that offer a quantitative description of DNA repair in single cells by measuring protein concentrations, diffusion characteristics, localizations, interactions, and enzymatic rates. Emerging single-molecule and super-resolution microscopy methods now permit direct visualization of individual proteins and DNA repair events in vivo. We expect much can be learned about the organization of DNA repair by linking cell heterogeneity to mechanistic observations at the molecular level.
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Affiliation(s)
- Stephan Uphoff
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
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