1
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Sangeeta, Mishra SK, Bhattacherjee A. Role of Shape Deformation of DNA-Binding Sites in Regulating the Efficiency and Specificity in Their Recognition by DNA-Binding Proteins. JACS AU 2024; 4:2640-2655. [PMID: 39055163 PMCID: PMC11267559 DOI: 10.1021/jacsau.4c00393] [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] [Received: 04/30/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 07/27/2024]
Abstract
Accurate transcription of genetic information is crucial, involving precise recognition of the binding motifs by DNA-binding proteins. While some proteins rely on short-range hydrophobic and hydrogen bonding interactions at binding sites, others employ a DNA shape readout mechanism for specific recognition. In this mechanism, variations in DNA shape at the binding motif resulted from either inherent flexibility or binding of proteins at adjacent sites are sensed and capitalized by the searching proteins to locate them specifically. Through extensive computer simulations, we investigate both scenarios to uncover the underlying mechanism and origin of specificity in the DNA shape readout mechanism. Our findings reveal that deformation in shape at the binding motif creates an entropy funnel, allowing information about altered shapes to manifest as fluctuations in minor groove widths. This signal enhances the efficiency of nonspecific search of nearby proteins by directing their movement toward the binding site, primarily driven by a gain in entropy. We propose this as a generic mechanism for DNA shape readout, where specificity arises from the alignment between the molecular frustration of the searching protein and the ruggedness of the entropic funnel governed by molecular features of the protein and arrangement of the DNA bases at the binding site, respectively.
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Affiliation(s)
- Sangeeta
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sujeet Kumar Mishra
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Arnab Bhattacherjee
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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2
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Rogoulenko E, Levy Y. Skipping events impose repeated binding attempts: profound kinetic implications of protein-DNA conformational changes. Nucleic Acids Res 2024; 52:6763-6776. [PMID: 38721783 PMCID: PMC11229352 DOI: 10.1093/nar/gkae333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/09/2024] [Accepted: 04/16/2024] [Indexed: 07/09/2024] Open
Abstract
The kinetics of protein-DNA recognition, along with its thermodynamic properties, including affinity and specificity, play a central role in shaping biological function. Protein-DNA recognition kinetics are characterized by two key elements: the time taken to locate the target site amid various nonspecific alternatives; and the kinetics involved in the recognition process, which may necessitate overcoming an energetic barrier. In this study, we developed a coarse-grained (CG) model to investigate interactions between a transcription factor called the sex-determining region Y (SRY) protein and DNA, in order to probe how DNA conformational changes affect SRY-DNA recognition and binding kinetics. We find that, not only does a requirement for such a conformational DNA transition correspond to a higher energetic barrier for binding and therefore slower kinetics, it may further impede the recognition kinetics by increasing unsuccessful binding events (skipping events) where the protein partially binds its DNA target site but fails to form the specific protein-DNA complex. Such skipping events impose the need for additional cycles protein search of nonspecific DNA sites, thus significantly extending the overall recognition time. Our results highlight a trade-off between the speed with which the protein scans nonspecific DNA and the rate at which the protein recognizes its specific target site. Finally, we examine molecular approaches potentially adopted by natural systems to enhance protein-DNA recognition despite its intrinsically slow kinetics.
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Affiliation(s)
- Elena Rogoulenko
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yaakov Levy
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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3
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Hall AN, Hall BW, Kinney KJ, Olsen GG, Banta AB, Noguera DR, Donohue TJ, Peters JM. Tools for Genetic Engineering and Gene Expression Control in Novosphingobium aromaticivorans and Rhodobacter sphaeroides. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.25.554875. [PMID: 37662258 PMCID: PMC10473679 DOI: 10.1101/2023.08.25.554875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Alphaproteobacteria have a variety of cellular and metabolic features that provide important insights into biological systems and enable biotechnologies. For example, some species are capable of converting plant biomass into valuable biofuels and bioproducts have the potential to form the backbone of the sustainable bioeconomy. Among the Alphaproteobacteria, Novosphingobium aromaticivorans, Rhodobacter sphaeroides, and Zymomonas mobilis, show particular promise as organisms that can be engineered to convert extracted plant lignin or sugars into bioproducts and biofuels. Genetic manipulation of these bacteria is needed to introduce engineered pathways and modulate expression of native genes with the goal of enhancing bioproduct output. Although recent work has expanded the genetic toolkit for Z. mobilis, N. aromaticivorans and R. sphaeroides still need facile, reliable approaches to deliver genetic payloads to the genome and to control gene expression. Here, we expand the platform of genetic tools for N. aromaticivorans and R. sphaeroides to address these issues. We demonstrate that Tn7 transposition is an effective approach for introducing engineered DNA into the chromosome of N. aromaticivorans and R. sphaeroides. We screen a synthetic promoter library to identify inducible promoters with strong, regulated activity in both organisms. Combining Tn7 integration with promoters from our library, we establish CRISPR interference systems for N. aromaticivorans and R. sphaeroides that can target essential genes and modulate engineered pathways. We anticipate that these systems will greatly facilitate both genetic engineering and gene function discovery efforts in these industrially important species and other Alphaproteobacteria.
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Affiliation(s)
- Ashley N. Hall
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Benjamin W. Hall
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kyle J. Kinney
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Gabby G. Olsen
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Amy B. Banta
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Daniel R. Noguera
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Timothy J. Donohue
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jason M. Peters
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, Wisconsin, USA
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4
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Lüking M, Elf J, Levy Y. Conformational Change of Transcription Factors from Search to Specific Binding: A lac Repressor Case Study. J Phys Chem B 2022; 126:9971-9984. [PMID: 36416228 PMCID: PMC9743208 DOI: 10.1021/acs.jpcb.2c05006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In a process known as facilitated diffusion, DNA-binding proteins find their target sites by combining three-dimensional diffusion and one-dimensional scanning of the DNA. Following the trade-off between speed and stability, agile exploration of DNA requires loose binding, whereas, at the DNA target site, the searching protein needs to establish tight interactions with the DNA. To enable both efficient search and stable binding, DNA-binding proteins and DNA often switch conformations upon recognition. Here, we study the one-dimensional diffusion and DNA binding of the dimeric lac repressor (LacI), which was reported to adopt two different conformations when binding different conformations of DNA. Using coarse-grained molecular dynamic simulations, we studied the diffusion and the sequence-specific binding of these conformations of LacI, as well as their truncated or monomeric variants, with two DNA conformations: straight and bent. The simulations were compared to experimental observables. This study supports that linear diffusion along DNA combines tight rotation-coupled groove tracking and rotation-decoupled hopping, where the protein briefly dissociates and reassociates just a few base pairs away. Tight groove tracking is crucial for target-site recognition, while hopping speeds up the overall search process. We investigated the diffusion of different LacI conformations on DNA and show how the flexibility of LacI's hinge regions ensures agility on DNA as well as faithful groove tracking. If the hinge regions instead form α-helices at the protein-DNA interface, tight groove tracking is not possible. On the contrary, the helical hinge region is essential for tight binding to bent, specific DNA, for the formation of the specific complex. Based on our study of different encounter complexes, we argue that the conformational change in LacI and DNA bending are somewhat coupled. Our findings underline the importance of two distinct protein conformations for facilitated diffusion and specific binding, respectively.
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Affiliation(s)
- Malin Lüking
- Department
of Cell- and Molecular Biology-ICM, Uppsala
University, Uppsala, Uppsala County751 24, Sweden
| | - Johan Elf
- Department
of Cell- and Molecular Biology-ICM, Uppsala
University, Uppsala, Uppsala County751 24, Sweden
| | - Yaakov Levy
- Department
of Chemical and Structural Biology, Weizmann
Institute of Science, Rehovot, Central District76100, Israel,. Tel.: 972-8-9344587
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5
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Kashchuk AV, Perederiy O, Caldini C, Gardini L, Pavone FS, Negriyko AM, Capitanio M. Particle Localization Using Local Gradients and Its Application to Nanometer Stabilization of a Microscope. ACS NANO 2022; 17:1344-1354. [PMID: 36383436 PMCID: PMC9878972 DOI: 10.1021/acsnano.2c09787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
Particle localization plays a fundamental role in advanced biological techniques such as single-molecule tracking, superresolution microscopy, and manipulation by optical and magnetic tweezers. Such techniques require fast and accurate particle localization algorithms as well as nanometer-scale stability of the microscope. Here, we present a universal method for three-dimensional localization of single labeled and unlabeled particles based on local gradient calculation of particle images. The method outperforms state-of-the-art localization techniques in high-noise conditions, and it is capable of 3D nanometer accuracy localization of nano- and microparticles with sub-millisecond calculation time. By localizing a fixed particle as fiducial mark and running a feedback loop, we demonstrate its applicability for active drift correction in sensitive nanomechanical measurements such as optical trapping and superresolution imaging. A multiplatform open software package comprising a set of tools for local gradient calculation in brightfield, darkfield, and fluorescence microscopy is shared for ready use by the scientific community.
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Affiliation(s)
- Anatolii V. Kashchuk
- Department
of Physics and Astronomy, University of
Florence, Via Sansone 1, Sesto Fiorentino, 50019, Italy
- LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
| | | | - Chiara Caldini
- LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
| | - Lucia Gardini
- LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
- National
Institute of Optics, National Research Council, Largo Fermi 6, 50125, Florence, Italy
| | - Francesco Saverio Pavone
- Department
of Physics and Astronomy, University of
Florence, Via Sansone 1, Sesto Fiorentino, 50019, Italy
- LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
- National
Institute of Optics, National Research Council, Largo Fermi 6, 50125, Florence, Italy
| | | | - Marco Capitanio
- Department
of Physics and Astronomy, University of
Florence, Via Sansone 1, Sesto Fiorentino, 50019, Italy
- LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
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6
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Mitra S, Oikawa H, Rajendran D, Kowada T, Mizukami S, Naganathan AN, Takahashi S. Flexible Target Recognition of the Intrinsically Disordered DNA-Binding Domain of CytR Monitored by Single-Molecule Fluorescence Spectroscopy. J Phys Chem B 2022; 126:6136-6147. [PMID: 35969476 PMCID: PMC9422980 DOI: 10.1021/acs.jpcb.2c02791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/03/2022] [Indexed: 11/29/2022]
Abstract
The intrinsically disordered DNA-binding domain of cytidine repressor (CytR-DBD) folds in the presence of target DNA and regulates the expression of multiple genes in E. coli. To explore the conformational rearrangements in the unbound state and the target recognition mechanisms of CytR-DBD, we carried out single-molecule Förster resonance energy transfer (smFRET) measurements. The smFRET data of CytR-DBD in the absence of DNA show one major and one minor population assignable to an expanded unfolded state and a compact folded state, respectively. The population of the folded state increases and decreases upon titration with salt and denaturant, respectively, in an apparent two-state manner. The peak FRET efficiencies of both the unfolded and folded states change continuously with denaturant concentration, demonstrating the intrinsic flexibility of the DNA-binding domain and the deviation from a strict two-state transition. Remarkably, the CytR-DBD exhibits a compact structure when bound to both the specific and nonspecific DNA; however, the peak FRET efficiencies of the two structures are slightly but consistently different. The observed conformational heterogeneity highlights the potential structural changes required for CytR to bind variably spaced operator sequences.
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Affiliation(s)
- Shrutarshi Mitra
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Hiroyuki Oikawa
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Divya Rajendran
- Department
of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Toshiyuki Kowada
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Shin Mizukami
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Athi N. Naganathan
- Department
of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Satoshi Takahashi
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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7
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α-catenin switches between a slip and an asymmetric catch bond with F-actin to cooperatively regulate cell junction fluidity. Nat Commun 2022; 13:1146. [PMID: 35241656 PMCID: PMC8894357 DOI: 10.1038/s41467-022-28779-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 02/10/2022] [Indexed: 12/11/2022] Open
Abstract
α-catenin is a crucial protein at cell junctions that provides connection between the actin cytoskeleton and the cell membrane. At adherens junctions (AJs), α-catenin forms heterodimers with β-catenin that are believed to resist force on F-actin. Outside AJs, α-catenin forms homodimers that regulates F-actin organization and directly connect the cell membrane to the actin cytoskeleton, but their mechanosensitive properties are inherently unknown. By using ultra-fast laser tweezers we found that a single α-β-catenin heterodimer does not resist force but instead slips along F-actin in the direction of force. Conversely, the action of 5 to 10 α-β-catenin heterodimers together with force applied toward F-actin pointed end engaged a molecular switch in α-catenin, which unfolded and strongly bound F-actin as a cooperative catch bond. Similarly, an α-catenin homodimer formed an asymmetric catch bond with F-actin triggered by protein unfolding under force. Our data suggest that α-catenin clustering together with intracellular tension engage a fluid-to-solid phase transition at the membrane-cytoskeleton interface.
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8
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Tripathy SK, Demidov VM, Gonchar IV, Wu S, Ataullakhanov FI, Grishchuk EL. Ultrafast Force-Clamp Spectroscopy of Microtubule-Binding Proteins. Methods Mol Biol 2022; 2478:609-650. [PMID: 36063336 PMCID: PMC9662813 DOI: 10.1007/978-1-0716-2229-2_22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Optical trapping has been instrumental for deciphering translocation mechanisms of the force-generating cytoskeletal proteins. However, studies of the dynamic interactions between microtubules (MTs) and MT-associated proteins (MAPs) with no motor activity are lagging. Investigating the motility of MAPs that can diffuse along MT walls is a particular challenge for optical-trapping assays because thermally driven motions rely on weak and highly transient interactions. Three-bead, ultrafast force-clamp (UFFC) spectroscopy has the potential to resolve static and diffusive translocations of different MAPs with sub-millisecond temporal resolution and sub-nanometer spatial precision. In this report, we present detailed procedures for implementing UFFC, including setup of the optical instrument and feedback control, immobilization and functionalization of pedestal beads, and preparation of MT dumbbells. Example results for strong static interactions were generated using the Kinesin-7 motor CENP-E in the presence of AMP-PNP. Time resolution for MAP-MT interactions in the UFFC assay is limited by the MT dumbbell relaxation time, which is significantly longer than reported for analogous experiments using actin filaments. UFFC, however, provides a unique opportunity for quantitative studies on MAPs that glide along MTs under a dragging force, as illustrated using the kinetochore-associated Ska complex.
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Affiliation(s)
- Suvranta K Tripathy
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI, USA
| | - Vladimir M Demidov
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Ivan V Gonchar
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russian Federation
| | - Shaowen Wu
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Agro-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Fazly I Ataullakhanov
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russian Federation
| | - Ekaterina L Grishchuk
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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9
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Gardini L, Woody MS, Kashchuk AV, Goldman YE, Ostap EM, Capitanio M. High-Speed Optical Traps Address Dynamics of Processive and Non-Processive Molecular Motors. Methods Mol Biol 2022; 2478:513-557. [PMID: 36063333 PMCID: PMC9987584 DOI: 10.1007/978-1-0716-2229-2_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Interactions between biological molecules occur on very different time scales, from the minutes of strong protein-protein bonds, down to below the millisecond duration of rapid biomolecular interactions. Conformational changes occurring on sub-ms time scales and their mechanical force dependence underlie the functioning of enzymes (e.g., motor proteins) that are fundamental for life. However, such rapid interactions are beyond the temporal resolution of most single-molecule methods. We developed ultrafast force-clamp spectroscopy (UFFCS), a single-molecule technique based on laser tweezers that allows us to investigate early and very fast dynamics of a variety of enzymes and their regulation by mechanical load. The technique was developed to investigate the rapid interactions between skeletal muscle myosin and actin, and then applied to the study of different biological systems, from cardiac myosin to processive myosin V, microtubule-binding proteins, transcription factors, and mechanotransducer proteins. Here, we describe two different implementations of UFFCS instrumentation and protocols using either acousto- or electro-optic laser beam deflectors, and their application to the study of processive and non-processive motor proteins.
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Affiliation(s)
- Lucia Gardini
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy
- National Institute of Optics, National Research Council (INO-CNR), Florence, Italy
| | - Michael S Woody
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Anatolii V Kashchuk
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy
- Department of Physics and Astronomy, University of Florence, Florence, Italy
| | - Yale E Goldman
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - E Michael Ostap
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - Marco Capitanio
- LENS, European Laboratory for Non-Linear Spectroscopy, Florence, Italy.
- Department of Physics and Astronomy, University of Florence, Florence, Italy.
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10
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Yang M, Sun R, Deng P, Yang Y, Wang W, Liu JJG, Chen C. Nonspecific interactions between SpCas9 and dsDNA sites located downstream of the PAM mediate facilitated diffusion to accelerate target search. Chem Sci 2021; 12:12776-12784. [PMID: 34703564 PMCID: PMC8494019 DOI: 10.1039/d1sc02633j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 08/19/2021] [Indexed: 12/27/2022] Open
Abstract
RNA-guided Streptococcus pyogenes Cas9 (SpCas9) is a sequence-specific DNA endonuclease that works as one of the most powerful genetic editing tools. However, how Cas9 locates its target among huge amounts of dsDNAs remains elusive. Here, combining biochemical and single-molecule fluorescence assays, we revealed that Cas9 uses both three-dimensional and one-dimensional diffusion to find its target with high efficiency. We further observed surprising apparent asymmetric target search regions flanking PAM sites on dsDNA under physiological salt conditions, which accelerates the target search efficiency of Cas9 by ∼10-fold. Illustrated by a cryo-EM structure of the Cas9/sgRNA/dsDNA dimer, non-specific interactions between DNA ∼8 bp downstream of the PAM site and lysines within residues 1151–1156 of Cas9, especially lys1153, are the key elements to mediate the one-dimensional diffusion of Cas9 and cause asymmetric target search regions flanking the PAM. Disrupting these non-specific interactions, such as mutating these lysines to alanines, diminishes the contribution of one-dimensional diffusion and reduces the target search rate by several times. In addition, low ionic concentrations or mutations on PAM recognition residues that modulate interactions between Cas9 and dsDNA alter apparent asymmetric target search behaviors. Together, our results reveal a unique searching mechanism of Cas9 under physiological salt conditions, and provide important guidance for both in vitro and in vivo applications of Cas9. Nonspecific interactions between DNA ∼8 bp downstream of the PAM and lysines within residues 1151–1156 of Cas9 mediate one-dimensional diffusion and cause asymmetric target search regions flanking the PAM.![]()
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Affiliation(s)
- Mengyi Yang
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China .,Laboratory of Nutrition and Development, Key Laboratory of Major Diseases in Children, Ministry of Education, Beijing Pediatric Research Institutue, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health Beijing 100045 China
| | - Ruirui Sun
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
| | - Pujuan Deng
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University Beijing China
| | - Yuzhuo Yang
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
| | - Wenjuan Wang
- School of Life Sciences, Technology Center for Protein Sciences, Tsinghua University Beijing China
| | - Jun-Jie Gogo Liu
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University Beijing China
| | - Chunlai Chen
- School of Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua University Beijing China
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11
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Ferreira RM, Ware AD, Matozel E, Price AC. Salt concentration modulates the DNA target search strategy of NdeI. Biochem Biophys Res Commun 2020; 534:1059-1063. [PMID: 33121681 DOI: 10.1016/j.bbrc.2020.10.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 10/14/2020] [Indexed: 11/29/2022]
Abstract
DNA target search is a key step in cellular transactions that access genomic information. How DNA binding proteins combine 3D diffusion, sliding and hopping into an overall search strategy remains poorly understood. Here we report the use of a single molecule DNA tethering method to characterize the target search kinetics of the type II restriction endonuclease NdeI. The measured search rate depends strongly on DNA length as well as salt concentration. Using roadblocks, we show that there are significant changes in the DNA sliding length over the salt concentrations in our study. To explain our results, we propose a model including cycles of 3D and 1D search in which salt concentration modulates the strategy by varying the length of DNA probed per 1D scan. At low salt NdeI makes a single non-specific encounter with DNA followed by an effective and complete 1D scan. At higher salt, NdeI must execute multiple cycles of target search due to the reduced efficacy of 1D search.
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Affiliation(s)
- Raquel M Ferreira
- Department of Biology, Emmanuel College, 400 the Fenway, Boston, MA, 02115, United States
| | - Anna D Ware
- Department of Biology, Emmanuel College, 400 the Fenway, Boston, MA, 02115, United States
| | - Emily Matozel
- Department of Biology, Emmanuel College, 400 the Fenway, Boston, MA, 02115, United States
| | - Allen C Price
- Department of Chemistry and Physics, Emmanuel College, 400 the Fenway, Boston, MA, 02115, United States.
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12
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Transient binding and jumping dynamics of p53 along DNA revealed by sub-millisecond resolved single-molecule fluorescence tracking. Sci Rep 2020; 10:13697. [PMID: 32792545 PMCID: PMC7426816 DOI: 10.1038/s41598-020-70763-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 08/04/2020] [Indexed: 12/14/2022] Open
Abstract
Characterization of the target search dynamics of DNA-binding proteins along DNA has been hampered by the time resolution of a standard single-molecule fluorescence microscopy. Here, we achieved the time resolution of 0.5 ms in the fluorescence microscopy measurements by optimizing the fluorescence excitation based on critical angle illumination and by utilizing the time delay integration mode of the electron-multiplying charge coupled device. We characterized the target search dynamics of the tumor suppressor p53 along nonspecific DNA at physiological salt concentrations. We identified a short-lived encounter intermediate before the formation of the long-lived p53–DNA complex. Both the jumps and the one-dimensional diffusion of p53 along DNA were accelerated at higher salt concentrations, suggesting the rotation-uncoupled movement of p53 along DNA grooves and conformational changes in the p53/DNA complex. This method can be used to clarify the unresolved dynamics of DNA-binding proteins previously hidden by time averaging.
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13
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Akpinar B, Haynes PJ, Bell NAW, Brunner K, Pyne ALB, Hoogenboom BW. PEGylated surfaces for the study of DNA-protein interactions by atomic force microscopy. NANOSCALE 2019; 11:20072-20080. [PMID: 31612171 PMCID: PMC6964798 DOI: 10.1039/c9nr07104k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Accepted: 09/22/2019] [Indexed: 05/20/2023]
Abstract
DNA-protein interactions are vital to cellular function, with key roles in the regulation of gene expression and genome maintenance. Atomic force microscopy (AFM) offers the ability to visualize DNA-protein interactions at nanometre resolution in near-physiological buffers, but it requires that the DNA be adhered to the surface of a solid substrate. This presents a problem when working in biologically relevant protein concentrations, where proteins may be present in large excess in solution; much of the biophysically relevant information can therefore be occluded by non-specific protein binding to the underlying substrate. Here we explore the use of PLLx-b-PEGy block copolymers to achieve selective adsorption of DNA on a mica surface for AFM studies. Through varying both the number of lysine and ethylene glycol residues in the block copolymers, we show selective adsorption of DNA on mica that is functionalized with a PLL10-b-PEG113/PLL1000-2000 mixture as viewed by AFM imaging in a solution containing high concentrations of streptavidin. We show - through the use of biotinylated DNA and streptavidin - that this selective adsorption extends to DNA-protein complexes and that DNA-bound streptavidin can be unambiguously distinguished in spite of an excess of unbound streptavidin in solution. Finally, we apply this to the nuclear enzyme PARP1, resolving the binding of individual PARP1 molecules to DNA by in-liquid AFM.
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Affiliation(s)
- Bernice Akpinar
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK. and Department of Chemistry, Imperial College London, SW7 2AZ, UK
| | - Philip J Haynes
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK. and Department of Chemistry, Imperial College London, SW7 2AZ, UK
| | | | - Katharina Brunner
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK and Discovery Biology, Discovery Sciences, R&D, AstraZeneca, 50F49, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG, UK
| | - Alice L B Pyne
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK. and Department of Materials Science and Engineering, University of Sheffield, S1 3JD, UK
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK. and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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14
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Munshi S, Gopi S, Asampille G, Subramanian S, Campos LA, Atreya HS, Naganathan AN. Tunable order-disorder continuum in protein-DNA interactions. Nucleic Acids Res 2019; 46:8700-8709. [PMID: 30107436 PMCID: PMC6158747 DOI: 10.1093/nar/gky732] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 07/31/2018] [Indexed: 11/23/2022] Open
Abstract
DNA-binding protein domains (DBDs) sample diverse conformations in equilibrium facilitating the search and recognition of specific sites on DNA over millions of energetically degenerate competing sites. We hypothesize that DBDs have co-evolved to sense and exploit the strong electric potential from the array of negatively charged phosphate groups on DNA. We test our hypothesis by employing the intrinsically disordered DBD of cytidine repressor (CytR) as a model system. CytR displays a graded increase in structure, stability and folding rate on increasing the osmolarity of the solution that mimics the non-specific screening by DNA phosphates. Electrostatic calculations and an Ising-like statistical mechanical model predict that CytR exhibits features of an electric potential sensor modulating its dimensions and landscape in a unique distance-dependent manner, while DNA plays the role of a non-specific macromolecular chaperone. Accordingly, CytR binds its natural half-site faster than the diffusion-controlled limit and even random DNA conforming to an electrostatic-steering binding mechanism. Our work unravels for the first time the synergistic features of a natural electrostatic potential sensor, a novel binding mechanism driven by electrostatic frustration and disorder, and the role of DNA in promoting distance-dependent protein structural transitions critical for switching between specific and non-specific DNA-binding modes.
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Affiliation(s)
- Sneha Munshi
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Soundhararajan Gopi
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | | | - Sandhyaa Subramanian
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Luis A Campos
- National Biotechnology Center, Consejo Superior de Investigaciones Científicas, Darwin 3, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Hanudatta S Atreya
- NMR Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Athi N Naganathan
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
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15
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Maffei M, Beneventi D, Canepari M, Bottinelli R, Pavone FS, Capitanio M. Ultra-fast force-clamp spectroscopy data on the interaction between skeletal muscle myosin and actin. Data Brief 2019; 25:104017. [PMID: 31223637 PMCID: PMC6565606 DOI: 10.1016/j.dib.2019.104017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/30/2019] [Accepted: 05/10/2019] [Indexed: 11/18/2022] Open
Abstract
Ultrafast force-clamp spectroscopy is a single molecule technique based on laser tweezers with sub-millisecond and sub-nanometer resolution. The technique has been successfully applied to investigate the rapid conformational changes that occur when a myosin II motor from skeletal muscle interacts with an actin filament. Here, we share data on the kinetics of such interaction and experimental records collected under different forces [1]. The data can be valuable for researchers interested in the mechanosensitive properties of myosin II, both from an experimental and modeling point of view. The data is related to the research article “ultrafast force-clamp spectroscopy of single molecules reveals load dependence of myosin working stroke” [2].
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Affiliation(s)
- Manuela Maffei
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Diego Beneventi
- LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
| | - Monica Canepari
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | | | - Francesco Saverio Pavone
- LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019 Sesto Fiorentino, Italy
- National Institute of Optics–National Research Council, Largo Fermi 6, 50125 Florence, Italy
| | - Marco Capitanio
- LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019 Sesto Fiorentino, Italy
- Corresponding author. LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
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16
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Sosa-Costa A, Piechocka IK, Gardini L, Pavone FS, Capitanio M, Garcia-Parajo MF, Manzo C. PLANT: A Method for Detecting Changes of Slope in Noisy Trajectories. Biophys J 2019; 114:2044-2051. [PMID: 29742398 DOI: 10.1016/j.bpj.2018.04.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 03/17/2018] [Accepted: 04/02/2018] [Indexed: 01/13/2023] Open
Abstract
Time traces obtained from a variety of biophysical experiments contain valuable information on underlying processes occurring at the molecular level. Accurate quantification of these data can help explain the details of the complex dynamics of biological systems. Here, we describe PLANT (Piecewise Linear Approximation of Noisy Trajectories), a segmentation algorithm that allows the reconstruction of time-trace data with constant noise as consecutive straight lines, from which changes of slopes and their respective durations can be extracted. We present a general description of the algorithm and perform extensive simulations to characterize its strengths and limitations, providing a rationale for the performance of the algorithm in the different conditions tested. We further apply the algorithm to experimental data obtained from tracking the centroid position of lymphocytes migrating under the effect of a laminar flow and from single myosin molecules interacting with actin in a dual-trap force-clamp configuration.
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Affiliation(s)
- Alberto Sosa-Costa
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain
| | - Izabela K Piechocka
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain
| | - Lucia Gardini
- LENS - European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy; National Institute of Optics-National Research Council, Florence, Italy
| | - Francesco S Pavone
- LENS - European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy; National Institute of Optics-National Research Council, Florence, Italy; Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
| | - Marco Capitanio
- LENS - European Laboratory for Non-linear Spectroscopy, Sesto Fiorentino, Italy; Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
| | - Maria F Garcia-Parajo
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain; ICREA, Barcelona, Spain
| | - Carlo Manzo
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain; Universitat de Vic - Universitat Central de Catalunya, Vic, Spain.
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17
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Monico C, Tempestini A, Gardini L, Pavone FS, Capitanio M. Data on the target search by a single protein on DNA measured with ultrafast force-clamp spectroscopy. Data Brief 2019; 24:103918. [PMID: 31193354 PMCID: PMC6526245 DOI: 10.1016/j.dib.2019.103918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 04/05/2019] [Accepted: 04/08/2019] [Indexed: 01/28/2023] Open
Abstract
The mechanism by which proteins are able to find small cognate sequences in the range from few to few tens of base pairs amongst the millions of non-specific chromosomal DNA has been puzzling researchers for decades. Single molecule techniques based on fluorescence have been successfully applied to investigate this process but are inherently limited in terms of spatial and temporal resolution. We previously showed that ultrafast force-clamp spectroscopy, a single molecule technique based on laser tweezers, can be applied to the study of protein-DNA interaction attaining sub-millisecond and few base-pair resolution. Here, we share experimental records of interactions between a single lactose repressor protein and DNA collected under different forces using our technique [1]. The data can be valuable for researchers interested in the study of protein-DNA interaction and the mechanism of DNA target search, both from an experimental and modeling point of view. The data is related to the research article "Sliding of a single lac repressor protein along DNA is tuned by DNA sequence and molecular switching" [2].
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Affiliation(s)
- Carina Monico
- LENS – European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
| | - Alessia Tempestini
- LENS – European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
| | - Lucia Gardini
- LENS – European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- National Institute of Optics–National Research Council, Largo Fermi 6, 50125, Florence, Italy
| | - Francesco Saverio Pavone
- LENS – European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019, Sesto Fiorentino, Italy
- National Institute of Optics–National Research Council, Largo Fermi 6, 50125, Florence, Italy
| | - Marco Capitanio
- LENS – European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019, Sesto Fiorentino, Italy
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18
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Abstract
Mechanical transitions in molecular motors often occur on a submillisecond time scale and rapidly follow binding of the motor with its cytoskeletal filament. Interactions of nonprocessive molecular motors with their filament can be brief and last for few milliseconds or fraction of milliseconds. The investigation of such rapid events and their load dependence requires specialized single-molecule tools. Ultrafast force-clamp spectroscopy is a constant-force optical tweezers technique that allows probing such rapid mechanical transitions and submillisecond kinetics of biomolecular interactions, which can be particularly valuable for the study of nonprocessive motors, single heads of processive motors, or stepping dynamics of processive motors. Here we describe a step-by-step protocol for the application of ultrafast force-clamp spectroscopy to myosin motors. We give indications on optimizing the optical tweezers setup, biological constructs, and data analysis to reach a temporal resolution of few tens of microseconds combined with subnanometer spatial resolution. The protocol can be easily generalized to other families of motor proteins.
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19
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Gardini L, Heissler SM, Arbore C, Yang Y, Sellers JR, Pavone FS, Capitanio M. Dissecting myosin-5B mechanosensitivity and calcium regulation at the single molecule level. Nat Commun 2018; 9:2844. [PMID: 30030431 PMCID: PMC6054644 DOI: 10.1038/s41467-018-05251-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 06/22/2018] [Indexed: 11/08/2022] Open
Abstract
Myosin-5B is one of three members of the myosin-5 family of actin-based molecular motors. Despite its fundamental role in recycling endosome trafficking and in collective actin network dynamics, the molecular mechanisms underlying its motility are inherently unknown. Here we combine single-molecule imaging and high-speed laser tweezers to dissect the mechanoenzymatic properties of myosin-5B. We show that a single myosin-5B moves processively in 36-nm steps, stalls at ~2 pN resistive forces, and reverses its directionality at forces >2 pN. Interestingly, myosin-5B mechanosensitivity differs from that of myosin-5A, while it is strikingly similar to kinesin-1. In particular, myosin-5B run length is markedly and asymmetrically sensitive to force, a property that might be central to motor ensemble coordination. Furthermore, we show that Ca2+ does not affect the enzymatic activity of the motor unit, but abolishes myosin-5B processivity through calmodulin dissociation, providing important insights into the regulation of postsynaptic cargoes trafficking in neuronal cells.
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Affiliation(s)
- Lucia Gardini
- LENS-European Laboratory for Non-linear Spectroscopy, University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- National Institute of Optics-National Research Council, Largo Fermi 6, 50125, Florence, Italy
| | - Sarah M Heissler
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892-8015, USA
| | - Claudia Arbore
- LENS-European Laboratory for Non-linear Spectroscopy, University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019, Sesto Fiorentino, Italy
| | - Yi Yang
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892-8015, USA
- Hunan Provincial Key Laboratory of Protein Engineering in Animal Vaccines, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892-8015, USA
| | - Francesco S Pavone
- LENS-European Laboratory for Non-linear Spectroscopy, University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy
- National Institute of Optics-National Research Council, Largo Fermi 6, 50125, Florence, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019, Sesto Fiorentino, Italy
| | - Marco Capitanio
- LENS-European Laboratory for Non-linear Spectroscopy, University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy.
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019, Sesto Fiorentino, Italy.
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20
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Woody MS, Capitanio M, Ostap EM, Goldman YE. Electro-optic deflectors deliver advantages over acousto-optical deflectors in a high resolution, ultra-fast force-clamp optical trap. OPTICS EXPRESS 2018; 26:11181-11193. [PMID: 29716042 PMCID: PMC6005679 DOI: 10.1364/oe.26.011181] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 03/30/2018] [Accepted: 03/30/2018] [Indexed: 06/02/2023]
Abstract
We characterized experimental artifacts arising from the non-linear response of acousto-optical deflectors (AODs) in an ultra-fast force-clamp optical trap and have shown that using electro-optical deflectors (EODs) instead eliminates these artifacts. We give an example of the effects of these artifacts in our ultra-fast force clamp studies of the interaction of myosin with actin filaments. The experimental setup, based on the concept of Capitanio et al. [Nat. Methods 9, 1013-1019 (2012)] utilizes a bead-actin-bead dumbbell held in two force-clamped optical traps which apply a load to the dumbbell to move it at a constant velocity. When myosin binds to actin, the filament motion stops quickly as the total force from the optical traps is transferred to the actomyosin attachment. We found that in our setup, AODs were unsuitable for beam steering due to non-linear variations in beam intensity and deflection angle as a function of driving frequency, likely caused by low-amplitude standing acoustic waves in the deflectors. These aberrations caused instability in the force feedback loops leading to artifactual jumps in the trap position. We demonstrate that beam steering with EODs improves the performance of our instrument. Combining the superior beam-steering capability of the EODs, force acquisition via back-focal-plane interferometry, and dual high-speed FPGA-based feedback loops, we apply precise and constant loads to study the dynamics of interactions between actin and myosin. The same concept applies to studies of other biomolecular interactions.
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Affiliation(s)
- Michael S. Woody
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
| | - Marco Capitanio
- LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Via Sansone 1, 50019 Sesto Fiorentino, Italy
| | - E. Michael Ostap
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
| | - Yale E. Goldman
- University of Pennsylvania, Pennsylvania Muscle Institute and Department of Physiology, 415 Curie Blvd, Philadelphia, Pennsylvania, USA 19104
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