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Fineberg A, Takagi Y, Thirumurugan K, Andrecka J, Billington N, Young G, Cole D, Burgess SA, Curd AP, Hammer JA, Sellers JR, Kukura P, Knight PJ. Myosin-5 varies its step length to carry cargo straight along the irregular F-actin track. Proc Natl Acad Sci U S A 2024; 121:e2401625121. [PMID: 38507449 PMCID: PMC10990141 DOI: 10.1073/pnas.2401625121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 02/15/2024] [Indexed: 03/22/2024] Open
Abstract
Molecular motors employ chemical energy to generate unidirectional mechanical output against a track while navigating a chaotic cellular environment, potential disorder on the track, and against Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.
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Affiliation(s)
- Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
- Laboratory of Single Molecule Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Kavitha Thirumurugan
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Neil Billington
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Daniel Cole
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Stan A. Burgess
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - Alistair P. Curd
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - John A. Hammer
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - James R. Sellers
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
- The Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, University of Oxford, OxfordOX1 3QU, United Kingdom
| | - Peter J. Knight
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
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2
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Fineberg A, Takagi Y, Thirumurugan K, Andrecka J, Billington N, Young G, Cole D, Burgess SA, Curd AP, Hammer JA, Sellers JR, Kukura P, Knight PJ. Myosin-5 varies its steps along the irregular F-actin track. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.16.549178. [PMID: 37503193 PMCID: PMC10370000 DOI: 10.1101/2023.07.16.549178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Molecular motors employ chemical energy to generate unidirectional mechanical output against a track. By contrast to the majority of macroscopic machines, they need to navigate a chaotic cellular environment, potential disorder in the track and Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering (iSCAT) microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably-spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.
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Affiliation(s)
- Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
- Laboratory of Single Molecule Biophysics, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, U.S.A
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, U.S.A
| | - Kavitha Thirumurugan
- Astbury Centre for Structural Molecular Biology, and Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, U.K
- Present address: Structural Biology Lab, Pearl Research Park, SBST, Vellore Institute of Technology, Vellore-632 014, India
| | - Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
- Present address: Human Technopole, Viale Rita Levi-Montalcini 1, 20157, Milan, Italy
| | - Neil Billington
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, U.S.A
- Present address: Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV, U.S.A
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
- Present address: Refeyn Ltd., Unit 9, Trade City, Sandy Ln W, Littlemore, Oxford OX4 6FF, U.K
| | - Daniel Cole
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
- Present address: Refeyn Ltd., Unit 9, Trade City, Sandy Ln W, Littlemore, Oxford OX4 6FF, U.K
| | - Stan A. Burgess
- Astbury Centre for Structural Molecular Biology, and Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, U.K
| | - Alistair P. Curd
- Astbury Centre for Structural Molecular Biology, and Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, U.K
| | - John A. Hammer
- Cell and Developmental Biology Center, NHLBI, National Institutes of Health, Bethesda, MD 20892, U.S.A
| | - James R. Sellers
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, U.S.A
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
- The Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, University of Oxford, South Parks Rd, Oxford OX1 3QU, U.K
| | - Peter J. Knight
- Astbury Centre for Structural Molecular Biology, and Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, U.K
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3
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Discovery of ultrafast myosin, its amino acid sequence, and structural features. Proc Natl Acad Sci U S A 2022; 119:2120962119. [PMID: 35173046 PMCID: PMC8872768 DOI: 10.1073/pnas.2120962119] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2022] [Indexed: 11/18/2022] Open
Abstract
Cytoplasmic streaming with extremely high velocity (∼70 μm s-1) occurs in cells of the characean algae (Chara). Because cytoplasmic streaming is caused by myosin XI, it has been suggested that a myosin XI with a velocity of 70 μm s-1, the fastest myosin measured so far, exists in Chara cells. However, the velocity of the previously cloned Chara corallina myosin XI (CcXI) was about 20 μm s-1, one-third of the cytoplasmic streaming velocity in Chara Recently, the genome sequence of Chara braunii has been published, revealing that this alga has four myosin XI genes. We cloned these four myosin XI (CbXI-1, 2, 3, and 4) and measured their velocities. While the velocities of CbXI-3 and CbXI-4 motor domains (MDs) were similar to that of CcXI MD, the velocities of CbXI-1 and CbXI-2 MDs were 3.2 times and 2.8 times faster than that of CcXI MD, respectively. The velocity of chimeric CbXI-1, a functional, full-length CbXI-1 construct, was 60 μm s-1 These results suggest that CbXI-1 and CbXI-2 would be the main contributors to cytoplasmic streaming in Chara cells and show that these myosins are ultrafast myosins with a velocity 10 times faster than fast skeletal muscle myosins in animals. We also report an atomic structure (2.8-Å resolution) of myosin XI using X-ray crystallography. Based on this crystal structure and the recently published cryo-electron microscopy structure of acto-myosin XI at low resolution (4.3-Å), it appears that the actin-binding region contributes to the fast movement of Chara myosin XI. Mutation experiments of actin-binding surface loops support this hypothesis.
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4
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Michalek AJ, Ali MY. Cargo properties play a critical role in myosin Va-driven cargo transport along actin filaments. Biochem Biophys Rep 2022; 29:101194. [PMID: 35024461 PMCID: PMC8733175 DOI: 10.1016/j.bbrep.2021.101194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 11/29/2022] Open
Abstract
High-resolution experiments revealed that a single myosin-Va motor can transport micron-sized cargo on actin filaments in a stepwise manner. However, intracellular cargo transport is mediated through the dense actin meshwork by a team of myosin Va motors. The mechanism of how motors interact mechanically to bring about efficient cargo transport is still poorly understood. This study describes a stochastic model where a quantitative understanding of the collective behaviors of myosin Va motors is developed based on cargo stiffness. To understand how cargo properties affect the overall cargo transport, we have designed a model in which two myosin Va motors were coupled by wormlike chain tethers with persistence length ranging from 10 to 80 nm and contour length from 100 to 200 nm, and predicted distributions of velocity, run length, and tether force. Our analysis showed that these parameters are sensitive to both the contour and persistence length of cargo. While the velocity of two couple motors is decreased compared to a single motor (from 531 ± 251 nm/s to as low as 318 ± 287 nm/s), the run length (716 ± 563 nm for a single motor) decreased for short, rigid tethers (to as low as 377 ± 187 μm) and increased for long, flexible tethers (to as high as 1.74 ± 1.50 μm). The sensitivity of processive properties to tether rigidity (persistence length) was greatest for short tethers, which caused the motors to exhibit close, yet anti-cooperative coordination. Motors coupled by longer tethers stepped more independently regardless of tether rigidity. Therefore, the properties of the cargo or linkage must play an essential role in motor-motor communication and cargo transport.
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Affiliation(s)
- Arthur J Michalek
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - M Yusuf Ali
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05403, USA
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5
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Fukuda S, Ando T. Faster high-speed atomic force microscopy for imaging of biomolecular processes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:033705. [PMID: 33820001 DOI: 10.1063/5.0032948] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/20/2021] [Indexed: 06/12/2023]
Abstract
High-speed atomic force microscopy (HS-AFM) has enabled observing protein molecules during their functional activity at rates of 1-12.5 frames per second (fps), depending on the imaging conditions, sample height, and fragility. To meet the increasing demand for the great expansion of observable dynamic molecular processes, faster HS-AFM with less disturbance is imperatively needed. However, even a 50% improvement in the speed performance imposes tremendous challenges, as the optimization of major rate-limiting components for their fast response is nearly matured. This paper proposes an alternative method that can lower the feedback control error and thereby enhance the imaging rate. This method can be implemented in any HS-AFM system by minor modifications of the software and hardware. The resulting faster and less-disturbing imaging capabilities are demonstrated by the imaging of relatively fragile actin filaments and microtubules near the video rate, and of actin polymerization that occurs through weak intermolecular interactions, at ∼8 fps.
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Affiliation(s)
- Shingo Fukuda
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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6
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Ando T. Studies on the impellers generating force in muscle. Biophys Rev 2020; 12:767-769. [PMID: 32529598 DOI: 10.1007/s12551-020-00705-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 06/05/2020] [Indexed: 02/01/2023] Open
Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan.
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7
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Single-Molecule Biophysical Techniques to Study Actomyosin Force Transduction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020. [PMID: 32451857 DOI: 10.1007/978-3-030-38062-5_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Inside the cellular environment, molecular motors can work in concert to conduct a variety of important physiological functions and processes that are vital for the survival of a cell. However, in order to decipher the mechanism of how these molecular motors work, single-molecule microscopy techniques have been popular methods to understand the molecular basis of the emerging ensemble behavior of these motor proteins.In this chapter, we discuss various single-molecule biophysical imaging techniques that have been used to expose the mechanics and kinetics of myosins. The chapter should be taken as a general overview and introductory guide to the many existing techniques; however, since other chapters will discuss some of these techniques more thoroughly, the readership should refer to those chapters for further details and discussions. In particular, we will focus on scattering-based single-molecule microscopy methods, some of which have become more popular in the recent years and around which the work in our laboratories has been centered.
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8
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Kodera N, Ando T. High-Speed Atomic Force Microscopy to Study Myosin Motility. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:127-152. [PMID: 32451858 DOI: 10.1007/978-3-030-38062-5_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
High-speed atomic force microscopy (HS-AFM) is a unique tool that enables imaging of protein molecules during their functional activity at sub-100 ms temporal and submolecular spatial resolution. HS-AFM is suited for the study of highly dynamic proteins, including myosin motors. HS-AFM images of myosin V walking on actin filaments provide irrefutable evidence for the swinging lever arm motion propelling the molecule forward. Moreover, molecular behaviors that have not been noticed before are also displayed on the AFM movies. This chapter describes the principle, underlying techniques and performance of HS-AFM, filmed images of myosin V, and mechanistic insights into myosin motility provided from the filmed images.
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Affiliation(s)
- Noriyuki Kodera
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan.
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9
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Venkatesh K, Mathew A, Koushika SP. Role of actin in organelle trafficking in neurons. Cytoskeleton (Hoboken) 2020; 77:97-109. [DOI: 10.1002/cm.21580] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/14/2019] [Accepted: 11/05/2019] [Indexed: 01/29/2023]
Affiliation(s)
- Keertana Venkatesh
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
| | - Amal Mathew
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
| | - Sandhya P. Koushika
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
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10
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Ando T. Biophysics in Kanazawa University. Biophys Rev 2020; 12:249-251. [PMID: 32060734 DOI: 10.1007/s12551-020-00635-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 02/03/2020] [Indexed: 11/24/2022] Open
Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan.
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11
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Hathcock D, Tehver R, Hinczewski M, Thirumalai D. Myosin V executes steps of variable length via structurally constrained diffusion. eLife 2020; 9:51569. [PMID: 31939739 PMCID: PMC7054003 DOI: 10.7554/elife.51569] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 01/14/2020] [Indexed: 11/16/2022] Open
Abstract
The molecular motor myosin V transports cargo by stepping on actin filaments, executing a random diffusive search for actin binding sites at each step. A recent experiment suggests that the joint between the myosin lever arms may not rotate freely, as assumed in earlier studies, but instead has a preferred angle giving rise to structurally constrained diffusion. We address this controversy through comprehensive analytical and numerical modeling of myosin V diffusion and stepping. When the joint is constrained, our model reproduces the experimentally observed diffusion, allowing us to estimate bounds on the constraint energy. We also test the consistency between the constrained diffusion model and previous measurements of step size distributions and the load dependence of various observable quantities. The theory lets us address the biological significance of the constrained joint and provides testable predictions of new myosin behaviors, including the stomp distribution and the run length under off-axis force.
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Affiliation(s)
- David Hathcock
- Department of Physics, Cornell University, Ithaca, United States
| | - Riina Tehver
- Department of Physics and Astronomy, Denison University, Granville, United States
| | - Michael Hinczewski
- Department of Physics, Case Western Reserve University, Cleveland, United States
| | - D Thirumalai
- Department of Chemistry, University of Texas, Austin, United States
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12
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Sellers JR, Takagi Y. How Myosin 5 Walks Deduced from Single-Molecule Biophysical Approaches. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:153-181. [PMID: 32451859 DOI: 10.1007/978-3-030-38062-5_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Myosin 5a is a two-headed myosin that functions as a cargo transporter in cells. To accomplish this task it has evolved several unique structural and kinetic features that allow it to move processively as a single molecule along actin filaments. A plethora of biophysical techniques have been used to elucidate the detailed mechanism of its movement along actin filaments in vitro. This chapter describes how this mechanism was deduced.
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Affiliation(s)
- James R Sellers
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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13
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Watanabe S, Kitazawa S, Sun L, Kodera N, Ando T. Development of high-speed ion conductance microscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:123704. [PMID: 31893861 DOI: 10.1063/1.5118360] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Scanning ion conductance microscopy (SICM) can image the surface topography of specimens in ionic solutions without mechanical probe-sample contact. This unique capability is advantageous for imaging fragile biological samples but its highest possible imaging rate is far lower than the level desired in biological studies. Here, we present the development of high-speed SICM. The fast imaging capability is attained by a fast Z-scanner with active vibration control and pipette probes with enhanced ion conductance. By the former, the delay of probe Z-positioning is minimized to sub-10 µs, while its maximum stroke is secured at 6 μm. The enhanced ion conductance lowers a noise floor in ion current detection, increasing the detection bandwidth up to 100 kHz. Thus, temporal resolution 100-fold higher than that of conventional systems is achieved, together with spatial resolution around 20 nm.
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Affiliation(s)
- Shinji Watanabe
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Satoko Kitazawa
- Department of Physics, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Linhao Sun
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Noriyuki Kodera
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Toshio Ando
- WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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14
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Zhang JP, Liu Y, Sun W, Zhao XY, Ta L, Guo WS. Characteristics of Myosin V Processivity. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2019; 16:1302-1308. [PMID: 28212094 DOI: 10.1109/tcbb.2017.2669311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Myosin V is a processive doubled-headed biomolecular motor involved in many intracellular organelle and vesicle transport. The unidirectional movement is coupled with the adenosine triphosphate (ATP) hydrolysis and product release cycle. With the progress of experimental techniques and the enhancement of measuring directness, detailed knowledge of the motility of myosin V has been obtained. Following the ATPase cycle, the 4-state mechanochemical model of the myosin V's processive movement is used. The transitions between various states take place in a stochastic manner. We can use the master equation to analyze and calculate quantitatively. Meanwhile, the effect of the reverse reaction is taken fully into account. We fit the mean velocity, the mean dwell time, the mean run length, and the ratio of forward/backward steps as a functionof ATP, ADP, and Pi concertration. The theoretical curves are generally in line with the experimental data. This work provides a new insight for the characteristic of myosin V.
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15
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Kodera N, Ando T. Direct Imaging of Walking Myosin V by High-Speed Atomic Force Microscopy. Methods Mol Biol 2019; 1805:103-122. [PMID: 29971715 DOI: 10.1007/978-1-4939-8556-2_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
High-speed atomic force microscopy allows for directly observing biological molecules in dynamic action at submolecular and sub-100 ms spatiotemporal resolution, without disturbing their function. This microscopy has recently been applied to various proteins with great success. Here, we describe methods to image myosin V molecules walking on actin filaments with high-speed atomic force microscopy.
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Affiliation(s)
- Noriyuki Kodera
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan.
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16
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Sasaki K, Kaya M, Higuchi H. A Unified Walking Model for Dimeric Motor Proteins. Biophys J 2018; 115:1981-1992. [PMID: 30396511 DOI: 10.1016/j.bpj.2018.09.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 08/29/2018] [Accepted: 09/24/2018] [Indexed: 01/17/2023] Open
Abstract
Dimeric motor proteins, kinesin-1, cytoplasmic dynein-1, and myosin-V, move stepwise along microtubules and actin filaments with a regular step size. The motors take backward as well as forward steps. The step ratio r and dwell time τ, which are the ratio of the number of backward steps to the number of forward steps and the time between consecutive steps, respectively, were observed to change with the load. To understand the movement of motor proteins, we constructed a unified and simple mathematical model to explain the load dependencies of r and of τ measured for the above three types of motors quantitatively. Our model consists of three states, and the forward and backward steps are represented by the cycles of transitions visiting different pairs of states among the three, implying that a backward step is not the reversal of a forward step. Each of r and τ is given by a simple expression containing two exponential functions. The experimental data for r and τ for dynein available in the literature are not sufficient for a quantitative analysis, which is in contrast to those for kinesin and myosin-V. We reanalyze the data to obtain r and τ of native dynein to make up the insufficient data to fit them to the model. Our model successfully describes the behavior of r and τ for all of the motors in a wide range of loads from large assisting loads to superstall loads.
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Affiliation(s)
- Kazuo Sasaki
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, Japan.
| | - Motoshi Kaya
- Department of Physics, University of Tokyo, Hongo Bunkyo-ku, Tokyo, Japan
| | - Hideo Higuchi
- Department of Physics, University of Tokyo, Hongo Bunkyo-ku, Tokyo, Japan; Universal Biology Institute, Graduate School of Science, University of Tokyo, Hongo Bunkyo-ku, Tokyo, Japan.
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17
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Sumi T. Myosin V: Chemomechanical-coupling ratchet with load-induced mechanical slip. Sci Rep 2017; 7:13489. [PMID: 29044145 PMCID: PMC5647391 DOI: 10.1038/s41598-017-13661-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 09/27/2017] [Indexed: 11/22/2022] Open
Abstract
A chemomechanical-network model for myosin V is presented on the basis of both the nucleotide-dependent binding affinity of the head to an actin filament (AF) and asymmetries and similarity relations among the chemical transitions due to an intramolecular strain of the leading and trailing heads. The model allows for branched chemomechanical cycles and takes into account not only two different force-generating mechanical transitions between states wherein the leading head is strongly bound and the trailing head is weakly bound to the AF but also load-induced mechanical-slip transitions between states in which both heads are strongly bound. The latter is supported by the fact that ATP-independent high-speed backward stepping has been observed for myosin V, although such motility has never been for kinesin. The network model appears as follows: (1) the high chemomechanical-coupling ratio between forward step and ATP hydrolysis is achieved even at low ATP concentrations by the dual mechanical transitions; (2) the forward stepping at high ATP concentrations is explained by the front head-gating mechanism wherein the power stroke is triggered by the inorganic-phosphate (Pi) release from the leading head; (3) the ATP-binding or hydrolyzed ADP.Pi-binding leading head produces a stable binding to the AF, especially against backward loading.
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Affiliation(s)
- Tomonari Sumi
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama, 700-8530, Japan. .,Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama, 700-8530, Japan.
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18
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Yamada Y, Konno H, Shimabukuro K. Demonstration of correlative atomic force and transmission electron microscopy using actin cytoskeleton. Biophys Physicobiol 2017; 14:111-117. [PMID: 28828286 PMCID: PMC5551270 DOI: 10.2142/biophysico.14.0_111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 06/29/2017] [Indexed: 12/01/2022] Open
Abstract
In this study, we present a new technique called correlative atomic force and transmission electron microscopy (correlative AFM/TEM) in which a targeted region of a sample can be observed under AFM and TEM. The ultimate goal of developing this new technique is to provide a technical platform to expand the fields of AFM application to complex biological systems such as cell extracts. Recent advances in the time resolution of AFM have enabled detailed observation of the dynamic nature of biomolecules. However, specifying molecular species, by AFM alone, remains a challenge. Here, we demonstrate correlative AFM/TEM, using actin filaments as a test sample, and further show that immuno-electron microscopy (immuno-EM), to specify molecules, can be integrated into this technique. Therefore, it is now possible to specify molecules, captured under AFM, by subsequent observation using immuno-EM. In conclusion, correlative AFM/TEM can be a versatile method to investigate complex biological systems at the molecular level.
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Affiliation(s)
- Yutaro Yamada
- Department of Chemical and Biological Engineering, National College of Technology, Ube College, Ube, Yamaguchi 755-8555, Japan
| | - Hiroki Konno
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Katsuya Shimabukuro
- Department of Chemical and Biological Engineering, National College of Technology, Ube College, Ube, Yamaguchi 755-8555, Japan
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19
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Ali MY, Vilfan A, Trybus KM, Warshaw DM. Cargo Transport by Two Coupled Myosin Va Motors on Actin Filaments and Bundles. Biophys J 2017; 111:2228-2240. [PMID: 27851945 DOI: 10.1016/j.bpj.2016.09.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 08/18/2016] [Accepted: 09/28/2016] [Indexed: 01/17/2023] Open
Abstract
Myosin Va (myoVa) is a processive, actin-based molecular motor essential for intracellular cargo transport. When a cargo is transported by an ensemble of myoVa motors, each motor faces significant physical barriers and directional challenges created by the complex actin cytoskeleton, a network of actin filaments and actin bundles. The principles that govern the interaction of multiple motors attached to the same cargo are still poorly understood. To understand the mechanical interactions between multiple motors, we developed a simple in vitro model in which two individual myoVa motors labeled with different-colored Qdots are linked via a third Qdot that acts as a cargo. The velocity of this two-motor complex was reduced by 27% as compared to a single motor, whereas run length was increased by only 37%, much less than expected from multimotor transport models. Therefore, at low ATP, which allowed us to identify individual motor steps, we investigated the intermotor dynamics within the two-motor complex. The randomness of stepping leads to a buildup of tension in the linkage between motors-which in turn slows down the leading motor-and increases the frequency of backward steps and the detachment rate. We establish a direct relationship between the velocity reduction and the distribution of intermotor distances. The analysis of run lengths and dwell times for the two-motor complex, which has only one motor engaged with the actin track, reveals that half of the runs are terminated by almost simultaneous detachment of both motors. This finding challenges the assumptions of conventional multimotor models based on consecutive motor detachment. Similar, but even more drastic, results were observed with two-motor complexes on actin bundles, which showed a run length that was even shorter than that of a single motor.
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Affiliation(s)
- M Yusuf Ali
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont.
| | | | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont
| | - David M Warshaw
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont
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20
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Andrecka J, Takagi Y, Mickolajczyk KJ, Lippert LG, Sellers JR, Hancock WO, Goldman YE, Kukura P. Interferometric Scattering Microscopy for the Study of Molecular Motors. Methods Enzymol 2016; 581:517-539. [PMID: 27793291 DOI: 10.1016/bs.mie.2016.08.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Our understanding of molecular motor function has been greatly improved by the development of imaging modalities, which enable real-time observation of their motion at the single-molecule level. Here, we describe the use of a new method, interferometric scattering microscopy, for the investigation of motor protein dynamics by attaching and tracking the motion of metallic nanoparticle labels as small as 20nm diameter. Using myosin-5, kinesin-1, and dynein as examples, we describe the basic assays, labeling strategies, and principles of data analysis. Our approach is relevant not only for motor protein dynamics but also provides a general tool for single-particle tracking with high spatiotemporal precision, which overcomes the limitations of single-molecule fluorescence methods.
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Affiliation(s)
- J Andrecka
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, United Kingdom
| | - Y Takagi
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - K J Mickolajczyk
- Pennsylvania State University, University Park, PA, United States; Intercollege Graduate Degree Program in Bioengineering, Pennsylvania State University, University Park, PA, United States
| | - L G Lippert
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - J R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - W O Hancock
- Pennsylvania State University, University Park, PA, United States; Intercollege Graduate Degree Program in Bioengineering, Pennsylvania State University, University Park, PA, United States
| | - Y E Goldman
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - P Kukura
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, United Kingdom.
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21
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Mazzocca A, Ferraro G, Misciagna G, Carr BI. A systemic evolutionary approach to cancer: Hepatocarcinogenesis as a paradigm. Med Hypotheses 2016; 93:132-7. [PMID: 27372872 DOI: 10.1016/j.mehy.2016.05.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 05/21/2016] [Indexed: 12/20/2022]
Abstract
The systemic evolutionary theory of cancer pathogenesis posits that cancer is generated by the de-emergence of the eukaryotic cell system and by the re-emergence of its archaea (genetic material and cytoplasm) and prokaryotic (mitochondria) subsystems with an uncoordinated behavior. This decreased coordination can be caused by a change in the organization of the eukaryote environment (mainly chronic inflammation), damage to mitochondrial DNA and/or to its membrane composition by many agents (e.g. viruses, chemicals, hydrogenated fatty acids in foods) or damage to nuclear DNA that controls mitochondrial energy production or metabolic pathways, including glycolysis. Here, we postulate that the two subsystems (the evolutionarily inherited archaea and the prokaryote) in a eukaryotic differentiated cell are well integrated, and produce the amount of clean energy that is constantly required to maintain the differentiated status. Conversely, when protracted injuries impair cell or tissue organization, the amount of energy necessary to maintain cell differentiation can be restricted, and this may cause gradual de-differentiation of the eukaryotic cell over time. In cirrhotic liver, for example, this process can be favored by reduced oxygen availability to the organ due to an altered vasculature and the fibrotic barrier caused by the disease. Thus, hepatocarcinogenesis is an ideal example to support our hypothesis. When cancer arises, the pre-eukaryote subsystems become predominant, as shown by the metabolic alterations of cancer cells (anaerobic glycolysis and glutamine utilization), and by their capacity for proliferation and invasion, resembling the primitive symbiotic components of the eukaryotic cell.
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Affiliation(s)
- Antonio Mazzocca
- Interdisciplinary Department of Medicine, University of Bari School of Medicine, Piazza G. Cesare, 11, 70124 Bari, Italy.
| | - Giovanni Ferraro
- Interuniversity Department of Physics, Polytechnic of Bari, Via Orabona, 4, 70126 Bari, Italy
| | - Giovanni Misciagna
- Scientific and Ethical Committee, University Hospital Policlinico, Piazza G. Cesare, 11, 70124 Bari, Italy
| | - Brian I Carr
- Izmir Biomedicine and Genome Center, Dokuz Eylul University, 35340 Balcova, Izmir, Turkey
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22
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Flexural Stiffness of Myosin Va Subdomains as Measured from Tethered Particle Motion. JOURNAL OF BIOPHYSICS 2015; 2015:465693. [PMID: 26770194 PMCID: PMC4685436 DOI: 10.1155/2015/465693] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/29/2015] [Accepted: 11/08/2015] [Indexed: 11/18/2022]
Abstract
Myosin Va (MyoVa) is a processive molecular motor involved in intracellular cargo transport on the actin cytoskeleton. The motor's processivity and ability to navigate actin intersections are believed to be governed by the stiffness of various parts of the motor's structure. Specifically, changes in calcium may regulate motor processivity by altering the motor's lever arm stiffness and thus its interhead communication. In order to measure the flexural stiffness of MyoVa subdomains, we use tethered particle microscopy, which relates the Brownian motion of fluorescent quantum dots, which are attached to various single- and double-headed MyoVa constructs bound to actin in rigor, to the motor's flexural stiffness. Based on these measurements, the MyoVa lever arm and coiled-coil rod domain have comparable flexural stiffness (0.034 pN/nm). Upon addition of calcium, the lever arm stiffness is reduced 40% as a result of calmodulins potentially dissociating from the lever arm. In addition, the flexural stiffness of the full-length MyoVa construct is an order of magnitude less stiff than both a single lever arm and the coiled-coil rod. This suggests that the MyoVa lever arm-rod junction provides a flexible hinge that would allow the motor to maneuver cargo through the complex intracellular actin network.
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23
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Toepfer C, Sellers JR. Use of fluorescent techniques to study the in vitro movement of myosins. EXPERIENTIA SUPPLEMENTUM (2012) 2014; 105:193-210. [PMID: 25095996 PMCID: PMC4178934 DOI: 10.1007/978-3-0348-0856-9_9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Myosins are a large superfamily of actin-dependent molecule motors that carry out many functions in cells. Some myosins are cargo carriers that move processively along actin which means that a single molecule of myosin can take many ATP-dependent steps on actin per initial encounter. Other myosins are designed to work in large ensembles such as myosin thick filaments. In vitro motility assays are a powerful method for studying the function of myosins. These assays in general use small amounts of protein, are simple to implement, and can be done on microscopes commonly found in many laboratories. There are two basic versions of the assay which involve different geometries. In the sliding actin in vitro motility assay, myosin molecules are bound to a coverslip surface in a simply constructed microscopic flow chamber. Fluorescently labeled actin filaments are added to the flow chamber in the presence of ATP, and the movement of these actin filaments powered by the surface-bound myosins is observed. This assay has been used widely for a variety of myosins including both processive and non-processive ones. From this assay, one can easily measure the rate at which myosin is translocating actin. The single-molecule motility assay uses an inverted geometry compared to the sliding actin in vitro motility assay. It is most useful for processive myosins. Here, actin filaments are affixed to the coverslip surface. Fluorescently labeled single molecules of myosins (usually ones with processive kinetics) are introduced, and the movement of single molecules along the actin filaments is observed. This assay typically uses total internal reflection fluorescent (TIRF) microscopy to reduce the background signal arising from myosins in solution. From this assay, one can measure the velocity of movement, the frequency of movement, and the run length. If sufficient photons can be collected, one can use Gaussian fitting of the point spread function to determine the position of the labeled myosin to within a few nanometers which allows for measurement of the step size and the stepping kinetics. Together, these two assays are powerful tools to elucidate myosin function.
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Affiliation(s)
- Christopher Toepfer
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - James R. Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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24
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Kodera N, Ando T. The path to visualization of walking myosin V by high-speed atomic force microscopy. Biophys Rev 2014; 6:237-260. [PMID: 25505494 PMCID: PMC4256461 DOI: 10.1007/s12551-014-0141-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 05/07/2014] [Indexed: 01/14/2023] Open
Abstract
The quest for understanding the mechanism of myosin-based motility started with studies on muscle contraction. From numerous studies, the basic frameworks for this mechanism were constructed and brilliant hypotheses were put forward. However, the argument about the most crucial issue of how the actin-myosin interaction generates contractile force and shortening has not been definitive. To increase the "directness of measurement", in vitro motility assays and single-molecule optical techniques were created and used. Consequently, detailed knowledge of the motility of muscle myosin evolved, which resulted in provoking more arguments to a higher level. In parallel with technical progress, advances in cell biology led to the discovery of many classes of myosins. Myosin V was discovered to be a processive motor, unlike myosin II. The processivity reduced experimental difficulties because it allowed continuous tracing of the motor action of single myosin V molecules. Extensive studies of myosin V were expected to resolve arguments and build a consensus but did not necessarily do so. The directness of measurement was further enhanced by the recent advent of high-speed atomic force microscopy capable of directly visualizing biological molecules in action at high spatiotemporal resolution. This microscopy clearly visualized myosin V molecules walking on actin filaments and at last provided irrefutable evidence for the swinging lever-arm motion propelling the molecules. However, a peculiar foot stomp behavior also appeared in the AFM movie, raising new questions of the chemo-mechanical coupling in this motor and myosin motors in general. This article reviews these changes in the research of myosin motility and proposes new ideas to resolve the newly raised questions.
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Affiliation(s)
- Noriyuki Kodera
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, 920-1192 Japan
- PREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, 332-0012 Japan
| | - Toshio Ando
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, 920-1192 Japan
- Department of Physics, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192 Japan
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, 332-0012 Japan
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25
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Belyy V, Yildiz A. Processive cytoskeletal motors studied with single-molecule fluorescence techniques. FEBS Lett 2014; 588:3520-5. [PMID: 24882363 DOI: 10.1016/j.febslet.2014.05.040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 05/19/2014] [Indexed: 11/18/2022]
Abstract
Processive cytoskeletal motors from the myosin, kinesin, and dynein families walk on actin filaments and microtubules to drive cellular transport and organization in eukaryotic cells. These remarkable molecular machines are able to take hundreds of successive steps at speeds of up to several microns per second, allowing them to effectively move vesicles and organelles throughout the cytoplasm. Here, we focus on single-molecule fluorescence techniques and discuss their wide-ranging applications to the field of cytoskeletal motor research. We cover both traditional fluorescence and sub-diffraction imaging of motors, providing examples of how fluorescence data can be used to measure biophysical parameters of motors such as coordination, stepping mechanism, gating, and processivity. We also outline some remaining challenges in the field and suggest future directions.
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Affiliation(s)
- Vladislav Belyy
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | - Ahmet Yildiz
- Department of Physics, University of California, Berkeley, CA 94720, USA; Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720, USA.
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26
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Wang N, Lo Presti L, Zhu YH, Kang M, Wu Z, Martin SG, Wu JQ. The novel proteins Rng8 and Rng9 regulate the myosin-V Myo51 during fission yeast cytokinesis. ACTA ACUST UNITED AC 2014; 205:357-75. [PMID: 24798735 PMCID: PMC4018781 DOI: 10.1083/jcb.201308146] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The myosin-V family of molecular motors is known to be under sophisticated regulation, but our knowledge of the roles and regulation of myosin-Vs in cytokinesis is limited. Here, we report that the myosin-V Myo51 affects contractile ring assembly and stability during fission yeast cytokinesis, and is regulated by two novel coiled-coil proteins, Rng8 and Rng9. Both rng8Δ and rng9Δ cells display similar defects as myo51Δ in cytokinesis. Rng8 and Rng9 are required for Myo51's localizations to cytoplasmic puncta, actin cables, and the contractile ring. Myo51 puncta contain multiple Myo51 molecules and walk continuously on actin filaments in rng8(+) cells, whereas Myo51 forms speckles containing only one dimer and does not move efficiently on actin tracks in rng8Δ. Consistently, Myo51 transports artificial cargos efficiently in vivo, and this activity is regulated by Rng8. Purified Rng8 and Rng9 form stable higher-order complexes. Collectively, we propose that Rng8 and Rng9 form oligomers and cluster multiple Myo51 dimers to regulate Myo51 localization and functions.
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Affiliation(s)
- Ning Wang
- Department of Molecular Genetics, 2 Department of Molecular and Cellular Biochemistry, and 3 Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
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27
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Ando T, Uchihashi T, Scheuring S. Filming biomolecular processes by high-speed atomic force microscopy. Chem Rev 2014; 114:3120-88. [PMID: 24476364 PMCID: PMC4076042 DOI: 10.1021/cr4003837] [Citation(s) in RCA: 250] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Toshio Ando
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Takayuki Uchihashi
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Simon Scheuring
- U1006
INSERM/Aix-Marseille Université, Parc Scientifique et Technologique
de Luminy Bâtiment Inserm TPR2 bloc 5, 163 avenue de Luminy, 13288 Marseille Cedex 9, France
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28
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Batters C, Veigel C, Homsher E, Sellers JR. To understand muscle you must take it apart. Front Physiol 2014; 5:90. [PMID: 24653704 PMCID: PMC3949407 DOI: 10.3389/fphys.2014.00090] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 02/16/2014] [Indexed: 01/08/2023] Open
Abstract
Striated muscle is an elegant system for study at many levels. Much has been learned about the mechanism of contraction from studying the mechanical properties of intact and permeabilized (or skinned) muscle fibers. Structural studies using electron microscopy, X-ray diffraction or spectroscopic probes attached to various contractile proteins were possible because of the highly ordered sarcomeric arrangement of actin and myosin. However, to understand the mechanism of force generation at a molecular level, it is necessary to take the system apart and study the interaction of myosin with actin using in vitro assays. This reductionist approach has lead to many fundamental insights into how myosin powers muscle contraction. In addition, nature has provided scientists with an array of muscles with different mechanical properties and with a superfamily of myosin molecules. Taking advantage of this diversity in myosin structure and function has lead to additional insights into common properties of force generation. This review will highlight the development of the major assays and methods that have allowed this combined reductionist and comparative approach to be so fruitful. This review highlights the history of biochemical and biophysical studies of myosin and demonstrates how a broad comparative approach combined with reductionist studies have led to a detailed understanding of how myosin interacts with actin and uses chemical energy to generate force and movement in muscle contraction and motility in general.
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Affiliation(s)
- Christopher Batters
- Department of Cellular Physiology and Centre for Nanosciences (CeNS), Ludwig-Maximilians-Universität München München, Germany
| | - Claudia Veigel
- Department of Cellular Physiology and Centre for Nanosciences (CeNS), Ludwig-Maximilians-Universität München München, Germany
| | - Earl Homsher
- Physiology Department, University of California Los Angeles Los Angeles, CA, USA
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
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29
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Fujita K, Iwaki M. Myosin V is a biological Brownian machine. Biophysics (Nagoya-shi) 2014; 10:69-75. [PMID: 27493501 PMCID: PMC4629658 DOI: 10.2142/biophysics.10.69] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 10/08/2014] [Indexed: 12/01/2022] Open
Abstract
Myosin V is a vesicle transporter that unidirectionally walks along cytoskeletal actin filaments by converting the chemical energy of ATP into mechanical work. Recently, it was found that myosin V force generation is a composition of two processes: a lever-arm swing, which involves a conformational change in the myosin molecule, and a Brownian search-and-catch, which involves a diffusive “search” by the motor domain that is followed by an asymmetric “catch” in the forward actin target such that Brownian motion is rectified. Here we developed a system that combines optical tweezers with DNA nano-material to show that the Brownian search-and-catch mechanism is the energetically dominant process at near stall force, providing 13 kBT of work compared to just 3 kBT by the lever-arm swing. Our result significantly reconsiders the lever-arm swinging model, which assumes the swing dominantly produces work (>10 kBT), and sheds light on the Brownian search-and-catch as a driving process.
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Affiliation(s)
- Keisuke Fujita
- Quantitative Biology Center, RIKEN, Suita, Osaka 565-0874, Japan
| | - Mitsuhiro Iwaki
- Quantitative Biology Center, RIKEN, Suita, Osaka 565-0874, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
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30
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Abstract
The molecular motor myosin V (MyoV) exhibits a wide repertoire of pathways during the stepping process, which is intimately connected to its biological function. The best understood of these is the hand-over-hand stepping by a swinging lever arm movement toward the plus end of actin filaments. Single-molecule experiments have also shown that the motor "foot stomps," with one hand detaching and rebinding to the same site, and back-steps under sufficient load. The complete taxonomy of MyoV's load-dependent stepping pathways, and the extent to which these are constrained by motor structure and mechanochemistry, are not understood. Using a polymer model, we develop an analytical theory to describe the minimal physical properties that govern motor dynamics. We solve the first-passage problem of the head reaching the target-binding site, investigating the competing effects of backward load, strain in the leading head biasing the diffusion in the direction of the target, and the possibility of preferential binding to the forward site due to the recovery stroke. The theory reproduces a variety of experimental data, including the power stroke and slow diffusive search regimes in the mean trajectory of the detached head, and the force dependence of the forward-to-backward step ratio, run length, and velocity. We derive a stall force formula, determined by lever arm compliance and chemical cycle rates. By exploring the MyoV design space, we predict that it is a robust motor whose dynamical behavior is not compromised by reasonable perturbations to the reaction cycle and changes in the architecture of the lever arm.
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31
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Bao J, Huck D, Gunther LK, Sellers JR, Sakamoto T. Actin structure-dependent stepping of myosin 5a and 10 during processive movement. PLoS One 2013; 8:e74936. [PMID: 24069366 PMCID: PMC3777900 DOI: 10.1371/journal.pone.0074936] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 08/07/2013] [Indexed: 11/22/2022] Open
Abstract
How myosin 10, an unconventional myosin, walks processively along actin is still controversial. Here, we used single molecule fluorescence techniques, TIRF and FIONA, to study the motility and the stepping mechanism of dimerized myosin 10 heavy-meromyosin-like fragment on both single actin filaments and two-dimensional F-actin rafts cross-linked by fascin or α-actinin. As a control, we also tracked and analyzed the stepping behavior of the well characterized processive motor myosin 5a. We have shown that myosin 10 moves processively along both single actin filaments and F-actin rafts with a step size of 31 nm. Moreover, myosin 10 moves more processively on fascin-F-actin rafts than on α-actinin-F-actin rafts, whereas myosin 5a shows no such selectivity. Finally, on fascin-F-actin rafts, myosin 10 has more frequent side steps to adjacent actin filaments than myosin 5a in the F-actin rafts. Together, these results reveal further single molecule features of myosin 10 on various actin structures, which may help to understand its cellular functions.
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Affiliation(s)
- Jianjun Bao
- Department of Physics and Astronomy, Wayne State University, Detroit, Michigan, United States of America
| | - Daniel Huck
- Department of Physics and Astronomy, Wayne State University, Detroit, Michigan, United States of America
| | - Laura K. Gunther
- Department of Physics and Astronomy, Wayne State University, Detroit, Michigan, United States of America
| | - James R. Sellers
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Takeshi Sakamoto
- Department of Physics and Astronomy, Wayne State University, Detroit, Michigan, United States of America
- Department of Physiology, School of Medicine, Wayne State University, Detroit, Michigan, United States of America
- * E-mail:
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32
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Abstract
Directly observing individual protein molecules in action at high spatiotemporal resolution has long been a holy grail for biological science. This is because we long have had to infer how proteins function from the static snapshots of their structures and dynamic behavior of optical makers attached to the molecules. This limitation has recently been removed to a large extent by the materialization of high-speed atomic force microscopy (HS-AFM). HS-AFM allows us to directly visualize the structure dynamics and dynamic processes of biological molecules in physiological solutions, at subsecond to sub-100-ms temporal resolution, without disturbing their function. In fact, dynamically acting molecules such as myosin V walking on an actin filament and bacteriorhodopsin in response to light are successfully visualized. In this review, we first describe theoretical considerations for the highest possible imaging rate of this new microscope, and then highlight recent imaging studies. Finally, the current limitation and future challenges to explore are described.
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Affiliation(s)
- Toshio Ando
- Department of Physics, Kanazawa University, Kanazawa 920-1192, Japan.
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33
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Tilting and wobble of myosin V by high-speed single-molecule polarized fluorescence microscopy. Biophys J 2013; 104:1263-73. [PMID: 23528086 DOI: 10.1016/j.bpj.2013.01.057] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 12/23/2012] [Accepted: 01/28/2013] [Indexed: 01/07/2023] Open
Abstract
Myosin V is biomolecular motor with two actin-binding domains (heads) that take multiple steps along actin by a hand-over-hand mechanism. We used high-speed polarized total internal reflection fluorescence (polTIRF) microscopy to study the structural dynamics of single myosin V molecules that had been labeled with bifunctional rhodamine linked to one of the calmodulins along the lever arm. With the use of time-correlated single-photon counting technology, the temporal resolution of the polTIRF microscope was improved ~50-fold relative to earlier studies, and a maximum-likelihood, multitrace change-point algorithm was used to objectively determine the times when structural changes occurred. Short-lived substeps that displayed an abrupt increase in rotational mobility were detected during stepping, likely corresponding to random thermal fluctuations of the stepping head while it searched for its next actin-binding site. Thus, myosin V harnesses its fluctuating environment to extend its reach. Additional, less frequent angle changes, probably not directly associated with steps, were detected in both leading and trailing heads. The high-speed polTIRF method and change-point analysis may be applicable to single-molecule studies of other biological systems.
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34
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Elting MW, Spudich JA. Future challenges in single-molecule fluorescence and laser trap approaches to studies of molecular motors. Dev Cell 2013; 23:1084-91. [PMID: 23237942 DOI: 10.1016/j.devcel.2012.10.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Single-molecule analysis is a powerful modern form of biochemistry, in which individual kinetic steps of a catalytic cycle of an enzyme can be explored in exquisite detail. Both single-molecule fluorescence and single-molecule force techniques have been widely used to characterize a number of protein systems. We focus here on molecular motors as a paradigm. We describe two areas where we expect to see exciting developments in the near future: first, characterizing the coupling of force production to chemical and mechanical changes in motors, and second, understanding how multiple motors work together in the environment of the cell.
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35
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Molecular machines directly observed by high-speed atomic force microscopy. FEBS Lett 2013; 587:997-1007. [PMID: 23318713 DOI: 10.1016/j.febslet.2012.12.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/15/2012] [Accepted: 12/17/2012] [Indexed: 11/22/2022]
Abstract
Molecular machines made of proteins are highly dynamic and carry out sophisticated biological functions. The direct and dynamic high-resolution visualization of molecular machines in action is considered to be the most straightforward approach to understanding how they function but this has long been infeasible until recently. High-speed atomic force microscopy has recently been realized, making such visualization possible. The captured images of myosin V, F1-ATPase, and bacteriorhodopsin have enabled their dynamic processes and structure dynamics to be revealed in great detail, giving unique and deep insights into their functional mechanisms.
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Schroeder HW, Hendricks AG, Ikeda K, Shuman H, Rodionov V, Ikebe M, Goldman YE, Holzbaur ELF. Force-dependent detachment of kinesin-2 biases track switching at cytoskeletal filament intersections. Biophys J 2012; 103:48-58. [PMID: 22828331 DOI: 10.1016/j.bpj.2012.05.037] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 05/11/2012] [Accepted: 05/22/2012] [Indexed: 12/20/2022] Open
Abstract
Intracellular trafficking of organelles often involves cytoskeletal track switching. Organelles such as melanosomes are transported by multiple motors including kinesin-2, dynein, and myosin-V, which drive switching between microtubules and actin filaments during dispersion and aggregation. Here, we used optical trapping to determine the unitary and ensemble forces of kinesin-2, and to reconstitute cargo switching at cytoskeletal intersections in a minimal system with kinesin-2 and myosin-V motors bound to beads. Single kinesin-2 motors exerted forces up to ∼5 pN, similar to kinesin-1. However, kinesin-2 motors were more likely to detach at submaximal forces, and the duration of force maintenance was short as compared to kinesin-1. In multimotor assays, force increased with kinesin-2 density but was not affected by the presence of myosin-V. In crossed filament assays, switching frequencies of motor-bound beads were dependent on the starting track. At equal average forces, beads tended to switch from microtubules onto overlying actin filaments consistent with the relatively faster detachment of kinesin-2 at near-maximal forces. Thus, in addition to relative force, switching probability at filament intersections is determined by the dynamics of motor-filament interaction, such as the quick detachment of kinesin-2 under load. This may enable fine-tuning of filament switching in the cell.
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Affiliation(s)
- Harry W Schroeder
- Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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37
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Switching of myosin-V motion between the lever-arm swing and brownian search-and-catch. Nat Commun 2012; 3:956. [PMID: 22805563 DOI: 10.1038/ncomms1934] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 05/30/2012] [Indexed: 01/26/2023] Open
Abstract
Motor proteins are force-generating nanomachines that are highly adaptable to their ever-changing biological environments and have a high energy conversion efficiency. Here we constructed an imaging system that uses optical tweezers and a DNA handle to visualize elementary mechanical processes of a nanomachine under load. We apply our system to myosin-V, a well-known motor protein that takes 72 nm 'hand-over-hand' steps composed of a 'lever-arm swing' and a 'brownian search-and-catch'. We find that the lever-arm swing generates a large proportion of the force at low load (<0.5 pN), resulting in 3 k(B)T of work. At high load (1.9 pN), however, the contribution of the brownian search-and-catch increases to dominate, reaching 13 k(B)T of work. We believe the ability to switch between these two force-generation modes facilitates myosin-V function at high efficiency while operating in a dynamic intracellular environment.
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38
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Guide to video recording of structure dynamics and dynamic processes of proteins by high-speed atomic force microscopy. Nat Protoc 2012; 7:1193-206. [DOI: 10.1038/nprot.2012.047] [Citation(s) in RCA: 192] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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39
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Coarse-grained simulation of myosin-V movement. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2012; 2012:781456. [PMID: 22675402 PMCID: PMC3366208 DOI: 10.1155/2012/781456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 03/01/2012] [Accepted: 03/14/2012] [Indexed: 11/22/2022]
Abstract
We describe the development of a hierarchic modelling method applied to simulating the processive movement of the myosin-V molecular motor protein along an actin filament track. In the hierarchic model, three different levels of protein structure resolution are represented: secondary structure, domain, and protein, with the level of detail changing according to the degree of interaction among the molecules. The integrity of the system is maintained using a tree of spatially organised bounding volumes and distance constraints. Although applied to an actin-myosin system, the hierarchic framework is general enough so that it may easily be adapted to a number of other large biomolecular systems containing in the order of 100 proteins. We compared the simulation results with biophysical data, and despite the lack of atomic detail in our model, we find good agreement and can even suggest some refinements to the current model of myosin-V motion.
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Lewis JH, Beausang JF, Sweeney HL, Goldman YE. The azimuthal path of myosin V and its dependence on lever-arm length. ACTA ACUST UNITED AC 2012; 139:101-20. [PMID: 22291144 PMCID: PMC3269788 DOI: 10.1085/jgp.201110715] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Myosin V (myoV) is a two-headed myosin capable of taking many successive steps along actin per diffusional encounter, enabling it to transport vesicular and ribonucleoprotein cargos in the dense and complex environment within cells. To better understand how myoV navigates along actin, we used polarized total internal reflection fluorescence microscopy to examine angular changes of bifunctional rhodamine probes on the lever arms of single myoV molecules in vitro. With a newly developed analysis technique, the rotational motions of the lever arm and the local orientation of each probe relative to the lever arm were estimated from the probe’s measured orientation. This type of analysis could be applied to similar studies on other motor proteins, as well as other proteins with domains that undergo significant rotational motions. The experiments were performed on recombinant constructs of myoV that had either the native-length (six IQ motifs and calmodulins [CaMs]) or truncated (four IQ motifs and CaMs) lever arms. Native-length myoV-6IQ mainly took straight steps along actin, with occasional small azimuthal tilts around the actin filament. Truncated myoV-4IQ showed an increased frequency of azimuthal steps, but the magnitudes of these steps were nearly identical to those of myoV-6IQ. The results show that the azimuthal deflections of myoV on actin are more common for the truncated lever arm, but the range of these deflections is relatively independent of its lever-arm length.
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Affiliation(s)
- John H Lewis
- The Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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41
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Wynne DJ, Rog O, Carlton PM, Dernburg AF. Dynein-dependent processive chromosome motions promote homologous pairing in C. elegans meiosis. ACTA ACUST UNITED AC 2012; 196:47-64. [PMID: 22232701 PMCID: PMC3255982 DOI: 10.1083/jcb.201106022] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Meiotic chromosome segregation requires homologue pairing, synapsis, and crossover recombination, which occur during meiotic prophase. Telomere-led chromosome motion has been observed or inferred to occur during this stage in diverse species, but its mechanism and function remain enigmatic. In Caenorhabditis elegans, special chromosome regions known as pairing centers (PCs), rather than telomeres, associate with the nuclear envelope (NE) and the microtubule cytoskeleton. In this paper, we investigate chromosome dynamics in living animals through high-resolution four-dimensional fluorescence imaging and quantitative motion analysis. We find that chromosome movement is constrained before meiosis. Upon prophase onset, constraints are relaxed, and PCs initiate saltatory, processive, dynein-dependent motions along the NE. These dramatic motions are dispensable for homologous pairing and continue until synapsis is completed. These observations are consistent with the idea that motions facilitate pairing by enhancing the search rate but that their primary function is to trigger synapsis. This quantitative analysis of chromosome dynamics in a living animal extends our understanding of the mechanisms governing faithful genome inheritance.
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Affiliation(s)
- David J Wynne
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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42
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Abstract
High-speed atomic force microscopy (HS-AFM) is now materialized. It allows direct visualization of dynamic structural changes and dynamic processes of functioning biological molecules in physiological solutions, at high spatiotemporal resolution. Dynamic molecular events unselectively appear in detail in an AFM movie, facilitating our understanding of how biological molecules operate to function. This review describes a historical overview of technical development towards HS-AFM, summarizes elementary devices and techniques used in the current HS-AFM, and then highlights recent imaging studies. Finally, future challenges of HS-AFM studies are briefly discussed.
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Affiliation(s)
- Toshio Ando
- Department of Physics and Bio-AFM Frontier Research Center, Kanazawa University, Kakuma-machi, Kanazawa, Japan
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43
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Full-length myosin Va exhibits altered gating during processive movement on actin. Proc Natl Acad Sci U S A 2012; 109:E218-24. [PMID: 22228305 DOI: 10.1073/pnas.1109709109] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myosin Va (myoV) is a processive molecular motor that transports intracellular cargo along actin tracks with each head taking multiple 72-nm hand-over-hand steps. This stepping behavior was observed with a constitutively active, truncated myoV, in which the autoinhibitory interactions between the globular tail and motor domains (i.e., heads) that regulate the full-length molecule no longer exist. Without cargo at near physiologic ionic strength (100 mM KCl), full-length myoV adopts a folded (approximately 15 S), enzymatically-inhibited state that unfolds to an extended (approximately 11 S), active conformation at higher salt (250 mM). Under conditions favoring the folded, inhibited state, we show that Quantum-dot-labeled myoV exhibits two types of interaction with actin in the presence of MgATP. Most motors bind to actin and remain stationary, but surprisingly, approximately 20% are processive. The moving motors transition between a strictly gated and hand-over-hand stepping pattern typical of a constitutively active motor, and a new mode with a highly variable stepping pattern suggestive of altered gating. Each head of this partially inhibited motor takes longer-lived, short forward (35 nm) and backward (28 nm) steps, presumably due to globular tail-head interactions that modify the gating of the individual heads. This unique mechanical state may be an intermediate in the pathway between the inhibited and active states of the motor.
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44
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Abstract
Cells use molecular motors, such as myosins, to move, position and segregate their organelles. Class V myosins possess biochemical and structural properties that should make them ideal actin-based cargo transporters. Indeed, studies show that class V myosins function as cargo transporters in yeast, moving a range of organelles, such as the vacuole, peroxisomes and secretory vesicles. There is also increasing evidence in vertebrate cells that class V myosins not only tether organelles to actin but also can serve as short-range, point-to-point organelle transporters, usually following long-range, microtubule-dependent organelle transport.
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45
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Abstract
The myosin superfamily is diverse in its structure, kinetic mechanisms and cellular function. The enzymatic activities of most myosins are regulated by some means such as Ca2+ ion binding, phosphorylation or binding of other proteins. In the present review, we discuss the structural basis for the regulation of mammalian myosin 5a and Drosophila myosin 7a. We show that, although both myosins have a folded inactive state in which domains in the myosin tail interact with the motor domain, the details of the regulation of these two myosins differ greatly.
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46
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Purcell TJ, Naber N, Sutton S, Cooke R, Pate E. EPR spectra and molecular dynamics agree that the nucleotide pocket of myosin V is closed and that it opens on binding actin. J Mol Biol 2011; 411:16-26. [PMID: 21640122 PMCID: PMC3143297 DOI: 10.1016/j.jmb.2011.05.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 05/11/2011] [Accepted: 05/11/2011] [Indexed: 10/18/2022]
Abstract
We have used EPR spectroscopy and computational modeling of nucleotide-analog spin probes to investigate conformational changes at the nucleotide site of myosin V. We find that, in the absence of actin, the mobility of a spin-labeled diphosphate analog [spin-labeled ADP (SLADP)] bound at the active site is strongly hindered, suggesting a closed nucleotide pocket. The mobility of the analog increases when the MV·SLADP complex (MV=myosin V) binds to actin, implying an opening of the active site in the A·MV·SLADP complex (A=actin). The probe mobilities are similar to those seen with myosin II, despite the fact that myosin V has dramatically altered kinetics. Molecular dynamics (MD) simulation was used to understand the EPR spectra in terms of the X-ray database. The X-ray structure of MV·ADP·BeFx shows a closed nucleotide site and has been proposed to be the detached state. The MV·ADP structure shows an open nucleotide site and has been proposed to be the A·MV·ADP state at the end of the working powerstroke. MD simulation of SLADP docked in the closed conformation gave a probe mobility comparable to that seen in the EPR spectrum of the MV·SLADP complex. The simulation of the open conformation gave a probe mobility that was 35-40° greater than that observed experimentally for the A·MV·SLADP state. Thus, EPR, X-ray diffraction, and computational analysis support the closed conformation as a myosin V state that is detached from actin. The MD results indicate that the MV·ADP crystal structure, which may correspond to the strained actin-bound post-powerstroke conformation resulting from head-head interaction in the dimeric processive motor, is superopened.
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Affiliation(s)
- Thomas J. Purcell
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Nariman Naber
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Shirley Sutton
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305
| | - Roger Cooke
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158
| | - Edward Pate
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164
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47
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Abstract
Over the past few decades, single molecule investigations employing optical tweezers, AFM and TIRF microscopy have revealed that molecular behaviors are typically characterized by discrete steps or events that follow changes in protein conformation. These events, that manifest as steps or jumps, are short-lived transitions between otherwise more stable molecular states. A major limiting factor in determining the size and timing of the steps is the noise introduced by the measurement system. To address this impediment to the analysis of single molecule behaviors, step detection algorithms incorporate large records of data and provide objective analysis. However, existing algorithms are mostly based on heuristics that are not reliable and lack objectivity. Most of these step detection methods require the user to supply parameters that inform the search for steps. They work well, only when the signal to noise ratio (SNR) is high and stepping speed is low. In this report, we have developed a novel step detection method that performs an objective analysis on the data without input parameters, and based only on the noise statistics. The noise levels and characteristics can be estimated from the data providing reliable results for much smaller SNR and higher stepping speeds. An iterative learning process drives the optimization of step-size distributions for data that has unimodal step-size distribution, and produces extremely low false positive outcomes and high accuracy in finding true steps. Our novel methodology, also uniquely incorporates compensation for the smoothing affects of probe dynamics. A mechanical measurement probe typically takes a finite time to respond to step changes, and when steps occur faster than the probe response time, the sharp step transitions are smoothed out and can obscure the step events. To address probe dynamics we accept a model for the dynamic behavior of the probe and invert it to reveal the steps. No other existing method addresses the impact of probe dynamics on step detection. Importantly, we have also developed a comprehensive set of tools to evaluate various existing step detection techniques. We quantify the performance and limitations of various step detection methods using novel evaluation scales. We show that under these scales, our method provides much better overall performance. The method is validated on different simulated test cases, as well as experimental data.
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48
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Shiroguchi K, Chin HF, Hannemann DE, Muneyuki E, De La Cruz EM, Kinosita K. Direct observation of the myosin Va recovery stroke that contributes to unidirectional stepping along actin. PLoS Biol 2011; 9:e1001031. [PMID: 21532738 PMCID: PMC3075224 DOI: 10.1371/journal.pbio.1001031] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 02/09/2011] [Indexed: 11/22/2022] Open
Abstract
Myosins are ATP-driven linear molecular motors that work as cellular force generators, transporters, and force sensors. These functions are driven by large-scale nucleotide-dependent conformational changes, termed "strokes"; the "power stroke" is the force-generating swinging of the myosin light chain-binding "neck" domain relative to the motor domain "head" while bound to actin; the "recovery stroke" is the necessary initial motion that primes, or "cocks," myosin while detached from actin. Myosin Va is a processive dimer that steps unidirectionally along actin following a "hand over hand" mechanism in which the trailing head detaches and steps forward ∼72 nm. Despite large rotational Brownian motion of the detached head about a free joint adjoining the two necks, unidirectional stepping is achieved, in part by the power stroke of the attached head that moves the joint forward. However, the power stroke alone cannot fully account for preferential forward site binding since the orientation and angle stability of the detached head, which is determined by the properties of the recovery stroke, dictate actin binding site accessibility. Here, we directly observe the recovery stroke dynamics and fluctuations of myosin Va using a novel, transient caged ATP-controlling system that maintains constant ATP levels through stepwise UV-pulse sequences of varying intensity. We immobilized the neck of monomeric myosin Va on a surface and observed real time motions of bead(s) attached site-specifically to the head. ATP induces a transient swing of the neck to the post-recovery stroke conformation, where it remains for ∼40 s, until ATP hydrolysis products are released. Angle distributions indicate that the post-recovery stroke conformation is stabilized by ≥ 5 k(B)T of energy. The high kinetic and energetic stability of the post-recovery stroke conformation favors preferential binding of the detached head to a forward site 72 nm away. Thus, the recovery stroke contributes to unidirectional stepping of myosin Va.
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Affiliation(s)
- Katsuyuki Shiroguchi
- Department of Physics, Faculty of Science and Engineering, Waseda
University, Tokyo, Japan
| | - Harvey F. Chin
- Department of Molecular Biophysics and Biochemistry, Yale University, New
Haven, Connecticut, United States of America
| | - Diane E. Hannemann
- Department of Molecular Biophysics and Biochemistry, Yale University, New
Haven, Connecticut, United States of America
| | - Eiro Muneyuki
- Department of Physics, Faculty of Science and Technology, Chuo
University, Tokyo, Japan
| | - Enrique M. De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New
Haven, Connecticut, United States of America
| | - Kazuhiko Kinosita
- Department of Physics, Faculty of Science and Engineering, Waseda
University, Tokyo, Japan
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49
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Video imaging of walking myosin V by high-speed atomic force microscopy. Nature 2010; 468:72-6. [PMID: 20935627 DOI: 10.1038/nature09450] [Citation(s) in RCA: 535] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 08/24/2010] [Indexed: 11/08/2022]
Abstract
The dynamic behaviour of myosin V molecules translocating along actin filaments has been mainly studied by optical microscopy. The processive hand-over-hand movement coupled with hydrolysis of adenosine triphosphate was thereby demonstrated. However, the protein molecules themselves are invisible in the observations and have therefore been visualized by electron microscopy in the stationary states. The concomitant assessment of structure and dynamics has been unfeasible, a situation prevailing throughout biological research. Here we directly visualize myosin V molecules walking along actin tracks, using high-speed atomic force microscopy. The high-resolution movies not only provide corroborative 'visual evidence' for previously speculated or demonstrated molecular behaviours, including lever-arm swing, but also reveal more detailed behaviours of the molecules, leading to a comprehensive understanding of the motor mechanism. Our direct and dynamic high-resolution visualization is a powerful new approach to studying the structure and dynamics of biomolecules in action.
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50
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Norstrom MF, Smithback PA, Rock RS. Unconventional processive mechanics of non-muscle myosin IIB. J Biol Chem 2010; 285:26326-34. [PMID: 20511646 DOI: 10.1074/jbc.m110.123851] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Proper tension maintenance in the cytoskeleton is essential for regulated cell polarity, cell motility, and division. Non-muscle myosin IIB (NMIIB) generates tension along actin filaments in many cell types, including neuronal, cardiac, and smooth muscle cells. Using a three-bead optical trapping assay, we recorded NMIIB interactions with actin filaments to determine if a NMIIB dimer cycles along an actin filament in a processive manner. Our results show that NMIIB is the first myosin II to exhibit evidence of processive stepping behavior. Analysis of these data reveals a forward displacement of 5.4 nm and, surprisingly, frequent backward steps of -5.9 nm. Processive stepping along the long pitch helix of actin may provide a mechanism for disassembly of fascin-actin bundles. Forward steps and detachment are weakly force-dependent at all forces, consistent with rate-limiting and force-dependent ADP release. However, backward steps are nearly force-independent. Our data support a model in which NMIIB can readily move in both directions at stall, which may be important for a general regulator of cytoskeleton tension.
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Affiliation(s)
- Melanie F Norstrom
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, USA
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