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Abstract
Directed movements on actin filaments within the cell are powered by molecular motors of the myosin superfamily. On actin filaments, myosin motors convert the energy from ATP into force and movement. Myosin motors power such diverse cellular functions as cytokinesis, membrane trafficking, organelle movements, and cellular migration. Myosin generates force and movement via a number of structural changes associated with hydrolysis of ATP, binding to actin, and release of the ATP hydrolysis products while bound to actin. Herein we provide an overview of those structural changes and how they relate to the actin-myosin ATPase cycle. These structural changes are the basis of chemo-mechanical transduction by myosin motors.
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2
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Katayama E, Kodera N. Unconventional Imaging Methods to Capture Transient Structures during Actomyosin Interaction. Int J Mol Sci 2018; 19:ijms19051402. [PMID: 29738465 PMCID: PMC5983842 DOI: 10.3390/ijms19051402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/04/2018] [Accepted: 05/05/2018] [Indexed: 11/30/2022] Open
Abstract
Half a century has passed since the cross-bridge structure was recognized as the molecular machine that generates muscle tension. Despite various approaches by a number of scientists, information on the structural changes in the myosin heads, particularly its transient configurations, remains scant even now, in part because of their small size and rapid stochastic movements during the power stroke. Though progress in cryo-electron microscopy is eagerly awaited as the ultimate means to elucidate structural details, the introduction of some unconventional methods that provide high-contrast raw images of the target protein assemblies is quite useful, if available, to break the current impasse. Quick-freeze deep–etch–replica electron microscopy coupled with dedicated image analysis procedures, and high-speed atomic-force microscopy are two such candidates. We have applied the former to visualize actin-associated myosin heads under in vitro motility assay conditions, and found that they take novel configurations similar to the SH1–SH2-crosslinked myosin that we characterized recently. By incorporating biochemical and biophysical results, we have revised the cross-bridge mechanism to involve the new conformer as an important main player. The latter “microscopy” is unique and advantageous enabling continuous observation of various protein assemblies as they function. Direct observation of myosin-V’s movement along actin filaments revealed several unexpected behaviors such as foot-stomping of the leading head and unwinding of the coiled-coil tail. The potential contribution of these methods with intermediate spatial resolution is discussed.
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Affiliation(s)
- Eisaku Katayama
- Waseda Research Institute for Science and Engineering, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
| | - Noriyuki Kodera
- WPI Nano Life Science Institute, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
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3
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Mariam J, Anand R. Fluorescence Quenching Studies of γ-Butyrolactone-Binding Protein (CprB) from Streptomyces coelicolor A3(2). Methods Mol Biol 2018; 1673:131-143. [PMID: 29130170 DOI: 10.1007/978-1-4939-7309-5_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fluorescence spectroscopy is an important analytical tool which is widely employed to study biological systems. This technique can be applied to qualitatively and quantitatively probe protein-ligand interactions primarily because of its sensitivity, selectivity, nondestructive and rapid form of analysis. In this chapter we describe the utility of this technique to establish a label-free, universal screening protocol for putative γ-butyrolactone (GBL) receptors by exploiting the intrinsic fluorescence of a highly conserved tryptophan residue that constitutes the hydrophobic pocket for GBL binding, a unique feature possessed by this family of receptors. Here we demonstrate this technique using a combination of steady-state fluorescence quenching methods and fluorescence lifetime decay kinetics using CprB protein from Streptomyces coelicolor A3(2) as a model system. Interaction data between CprB and two chemically synthesized GBLs involved in quorum sensing, Cp1 and Cp2, have been used as example.
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Affiliation(s)
- Jessy Mariam
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra, 400076, India
| | - Ruchi Anand
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra, 400076, India.
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4
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Zhang Y, Tang ZY, Kohama K, Lin Y. Interaction between myosin and a trace amount of caldesmon. J Biochem 2011; 150:267-70. [DOI: 10.1093/jb/mvr084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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5
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Andrade FK, Silva JP, Carvalho M, Castanheira EMS, Soares R, Gama M. Studies on the hemocompatibility of bacterial cellulose. J Biomed Mater Res A 2011; 98:554-66. [DOI: 10.1002/jbm.a.33148] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 04/01/2011] [Accepted: 04/15/2011] [Indexed: 01/10/2023]
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6
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Takács B, O'Neall-Hennessey E, Hetényi C, Kardos J, Szent-Györgyi AG, Kovács M. Myosin cleft closure determines the energetics of the actomyosin interaction. FASEB J 2010; 25:111-21. [PMID: 20837775 DOI: 10.1096/fj.10-164871] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Formation of the strong binding interaction between actin and myosin is essential for force generation in muscle and in cytoskeletal motor systems. To clarify the role of the closure of myosin's actin-binding cleft in the actomyosin interaction, we performed rapid kinetic, spectroscopic, and calorimetric experiments and atomic-level energetic calculations on a variety of myosin isoforms for which atomic structures are available. Surprisingly, we found that the endothermic actin-binding profile of vertebrate skeletal muscle myosin subfragment-1 is unique among studied myosins. We show that the diverse propensity of myosins for cleft closure determines different energetic profiles as well as structural and kinetic pathways of actin binding. Depending on the type of myosin, strong actin binding may occur via induced-fit or conformational preselection mechanisms. However, cleft closure does not directly determine the kinetics and affinity of actin binding. We also show that cleft closure is enthalpically unfavorable, reflecting the development of an internal strain within myosin in order to adopt precise steric complementarity to the actin filament. We propose that cleft closure leads to an increase in the torsional strain of myosin's central β-sheet that has been proposed to serve as an allosteric energy-transducing spring during force generation.
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Affiliation(s)
- Balázs Takács
- Department of Biochemistry, Eötvös University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary
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7
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Abstract
The general structural features of the motor region of myosin superfamily members are now well established, as is a subset of the structural and kinetic transitions of the actin-myosin catalytic cycle. Not yet visualized are the structural rearrangements triggered by actin binding that are coupled to force generation and product release. In this review we describe the recent progress in understanding these missing components of the mechanism of chemomechanical transduction by myosin motors. These insights come from a combination of kinetic and single-molecule studies on multiple classes of myosins, with additional insights from contracting muscle fibers. These recent studies have explored the effects of intermediate and high loads on the kinetics of the actin-bound myosin state transitions. We also describe studies that delineate how some classes of myosin motors are adapted for processive movement on actin.
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Affiliation(s)
- H Lee Sweeney
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6085, USA.
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8
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Guo B, Guilford WH. Mechanics of actomyosin bonds in different nucleotide states are tuned to muscle contraction. Proc Natl Acad Sci U S A 2006; 103:9844-9. [PMID: 16785439 PMCID: PMC1502541 DOI: 10.1073/pnas.0601255103] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Muscle contraction and many other cell movements are driven by cyclic interactions between actin filaments and the motor enzyme myosin. Conformational changes in the actin-myosin binding interface occur in concert with the binding of ATP, binding to actin, and loss of hydrolytic by-products, but the effects of these conformational changes on the strength of the actomyosin bond are unknown. The force-dependent kinetics of the actomyosin bond may be particularly important at high loads, where myosin may detach from actin before achieving its full power stroke. Here we show that over a physiological range of rapidly applied loads, actomyosin behaves as a "catch" bond, characterized by increasing lifetimes with increasing loads up to a maximum at approximately 6 pN. Surprisingly, we found that the myosin-ADP bond is possessed of longer lifetimes under load than rigor bonds, although the load at which bond lifetime is maximal remains unchanged. We also found that actomyosin bond lifetime is ultimately dependent not only on load, but loading history as well. These data suggest a complex relationship between the rate of actomyosin dissociation and muscle force and shortening velocity. The 6-pN load for maximum bond lifetime is near the force generated by a single myosin molecule during isometric contraction. This raises the possibility that all catch bonds between load-bearing molecules are "mechanokinetically" tuned to their physiological environment.
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Affiliation(s)
- Bin Guo
- Department of Biomedical Engineering, University of Virginia, Box 800759, Charlottesville, VA 22908
| | - William H. Guilford
- Department of Biomedical Engineering, University of Virginia, Box 800759, Charlottesville, VA 22908
- To whom correspondence should be addressed. E-mail:
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9
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Kambara T, Ikebe M. A unique ATP hydrolysis mechanism of single-headed processive myosin, myosin IX. J Biol Chem 2005; 281:4949-57. [PMID: 16338935 DOI: 10.1074/jbc.m509141200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent studies have revealed that myosin IX is a single-headed processive myosin, yet it is unclear how myosin IX can achieve the processive movement. Here we studied the mechanism of ATP hydrolysis cycle of actomyosin IXb. We found that myosin IXb has a rate-limiting ATP hydrolysis step unlike other known myosins, thus populating the prehydrolysis intermediate (M.ATP). M.ATP has a high affinity for actin, and, unlike other myosins, the dissociation of M.ATP from actin was extremely slow, thus preventing myosin from dissociating away from actin. The ADP dissociation step was 10-fold faster than the overall ATP hydrolysis cycle rate and thus not rate-limiting. We propose the following model for single-headed processive myosin. Upon the formation of the M.ATP intermediate, the tight binding of actomyosin IX at the interface is weakened. However, the head is kept in close proximity to actin due to the tethering role of loop 2/large unique insertion of myosin IX. There is enough freedom for the myosin head to find the next location of the binding site along with the actin filament before complete dissociation from the filament. After ATP hydrolysis, Pi is quickly released to form a strong actin binding form, and a power stroke takes place.
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Affiliation(s)
- Taketoshi Kambara
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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10
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van Duffelen M, Chrin LR, Berger CL. Kinetics of structural changes in the relay loop and SH3 domain of myosin. Biochem Biophys Res Commun 2005; 329:563-72. [PMID: 15737623 DOI: 10.1016/j.bbrc.2005.01.152] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Indexed: 11/27/2022]
Abstract
The intrinsic fluorescence of smooth muscle myosin signals conformational changes associated with different catalytic states of the ATPase cycle. To elucidate this relationship, we have examined the pre-steady-state kinetics of nucleotide binding, hydrolysis, and product release in motor domain-essential light chain mutants containing a single endogenous tryptophan, either residue 512 in the rigid relay loop or residue 29 adjacent to the SH3 domain. The intrinsic fluorescence of W512 is sensitive to both nucleotide binding and hydrolysis, and appears to report structural changes at the active site, presumably through a direct connection with switch II. The intrinsic fluorescence of W29 is sensitive to nucleotide binding but not hydrolysis, and does not appear to be tightly linked with structural changes occurring at the active site. We propose that the SH3 domain may be sensitive to conformational changes in the lever arm through contacts with the essential light chain.
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Affiliation(s)
- Marilyn van Duffelen
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, VT 05405-0075, USA
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11
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Spivak V, Lin A, Beebe P, Stoll L, Gentile L. Identification of a neurosteroid binding site contained within the GluR2-S1S2 domain. Lipids 2005; 39:811-9. [PMID: 15638252 DOI: 10.1007/s11745-004-1301-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glutamate receptors play a major role in neural cell plasticity, growth, and maturation. The degree to which ionotropic glutamate receptors (iGluR) conduct current is dependent on binding of extracellular ligands, of which glutamate is the native agonist. Although the glutamate binding site of the GluR2 class of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) iGluR has been structurally characterized, the allosteric sites attributed to neurosteroid binding have yet to be localized. Here, using intrinsic tryptophan fluorescence spectroscopy, we show that the extracellular glutamate binding core of the GluR2 class of AMPA receptors also binds to two neurosteroids, pregnenolone sulfate (PS) and 3alpha-hydroxy-5beta-pregnan-20-one sulfate, both of which negatively modulate its activity. Interest in these sulfated neurosteroids stems from their differential modulation of other members of the iGluR family and their potential use as endogeneous agents for stroke therapy. In particular, whereas PS inhibits AMPA and other non-N-methyl-D-aspartate (NMDA) family members, it activates the NMDA receptor. In addition to providing evidence for binding of these neurosteroids to the glutamate binding core of the GluR2 class of AMPA receptors, our data suggests that both neurosteroids bind in a similar manner, consistent with their modulation of activity of this class of iGluR. Interestingly, the conformational change induced upon binding of these neurosteroids is distinct from that induced upon glutamate binding.
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Affiliation(s)
- Vlad Spivak
- Department of Chemistry, Western Washington University, Bellingham, Washington 98225-9150, USA
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12
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Patchell VB, Gallon CE, Evans JS, Gao Y, Perry SV, Levine BA. The regulatory effects of tropomyosin and troponin-I on the interaction of myosin loop regions with F-actin. J Biol Chem 2005; 280:14469-75. [PMID: 15695827 DOI: 10.1074/jbc.m414202200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The N terminus of skeletal myosin light chain 1 and the cardiomyopathy loop of human cardiac myosin have been shown previously to bind to actin in the presence and absence of tropomyosin (Patchell, V. B., Gallon, C. E., Hodgkin, M. A., Fattoum, A., Perry, S. V., and Levine, B. A. (2002) Eur. J. Biochem. 269, 5088-5100). We have extended this work and have shown that segments corresponding to other regions of human cardiac beta-myosin, presumed to be sites of interaction with F-actin (residues 554-584, 622-646, and 633-660), likewise bind independently to actin under similar conditions. The binding to F-actin of a peptide spanning the minimal inhibitory segment of human cardiac troponin I (residues 134-147) resulted in the dissociation from F-actin of all the myosin peptides bound to it either individually or in combination. Troponin C neutralized the effect of the inhibitory peptide on the binding of the myosin peptides to F-actin. We conclude that the binding of the inhibitory region of troponin I to actin, which occurs during relaxation in muscle when the calcium concentration is low, imposes conformational changes that are propagated to different locations on the surface of actin. We suggest that the role of tropomyosin is to facilitate the transmission of structural changes along the F-actin filament so that the monomers within a structural unit are able to interact with myosin.
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Affiliation(s)
- Valerie B Patchell
- Division of Medical Sciences, School of Medicine, University of Birmingham, Birmingham B15 2TT, United Kingdom
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13
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Sweeney HL, Houdusse A. The motor mechanism of myosin V: insights for muscle contraction. Philos Trans R Soc Lond B Biol Sci 2005; 359:1829-41. [PMID: 15647159 PMCID: PMC1693472 DOI: 10.1098/rstb.2004.1576] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
It is 50 years since the sliding of actin and myosin filaments was proposed as the basis of force generation and shortening in striated muscle. Although this is now generally accepted, the detailed molecular mechanism of how myosin uses adenosine triphosphate to generate force during its cyclic interaction with actin is only now being unravelled. New insights have come from the unconventional myosins, especially myosin V. Myosin V is kinetically tuned to allow movement on actin filaments as a single molecule, which has led to new kinetic, mechanical and structural data that have filled in missing pieces of the actomyosin-chemo-mechanical transduction puzzle.
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Affiliation(s)
- H Lee Sweeney
- Department of Physiology, University of Pennsylvania School of Medicine, A700 Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104-6085, USA.
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14
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Wakelin S, Conibear PB, Woolley RJ, Floyd DN, Bagshaw CR, Kovács M, Málnási-Csizmadia A. Engineering Dictyostelium discoideum myosin II for the introduction of site-specific fluorescence probes. J Muscle Res Cell Motil 2003; 23:673-83. [PMID: 12952066 DOI: 10.1023/a:1024411208497] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Dictyostelium discoideum is a useful host for the production of constructs for the analysis of structure-function relationships of myosin. Here we describe the use of myosin II constructs containing a single tryptophan residue, at different locations, for probing events at the nucleotide binding site, the relay loop and the communication path between them. GFP fusions have also been expressed at the N- and C-termini of the myosin motor to provide sensitive probes of the actomyosin dissociation reaction in microscope-based kinetic assays. We report on the fluorescence anisotropy of these constructs in the context of their use as resonance energy transfer probes.
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Affiliation(s)
- Stuart Wakelin
- Department of Biochemistry, University of Leicester, Leicester LE1 7RH, United Kingdom
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15
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Kovacs M, Malnasi-Csizmadia A, Woolley RJ, Bagshaw CR. Analysis of nucleotide binding to Dictyostelium myosin II motor domains containing a single tryptophan near the active site. J Biol Chem 2002; 277:28459-67. [PMID: 11971905 DOI: 10.1074/jbc.m202180200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dictyostelium myosin II motor domain constructs containing a single tryptophan residue near the active sites were prepared in order to characterize the process of nucleotide binding. Tryptophan was introduced at positions 113 and 131, which correspond to those naturally present in vertebrate skeletal muscle myosin, as well as position 129 that is also close to the adenine binding site. Nucleotide (ATP and ADP) binding was accompanied by a large quench in protein fluorescence in the case of the tryptophans at 129 and 131 but a small enhancement for that at 113. None of these residues was sensitive to the subsequent open-closed transition that is coupled to hydrolysis (i.e. ADP and ATP induced similar fluorescence changes). The kinetics of the fluorescence change with the F129W mutant revealed at least a three-step nucleotide binding mechanism, together with formation of a weakly competitive off-line intermediate that may represent a nonproductive mode of nucleotide binding. Overall, we conclude that the local and global conformational changes in myosin IIs induced by nucleotide binding are similar in myosins from different species, but the sign and magnitude of the tryptophan fluorescence changes reflect nonconserved residues in the immediate vicinity of each tryptophan. The nucleotide binding process is at least three-step, involving conformational changes that are quite distinct from the open-closed transition sensed by the tryptophan Trp(501) in the relay loop.
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Affiliation(s)
- Mihaly Kovacs
- Department of Biochemistry, University of Leicester, Leicester LE1 7RH, United Kingdom
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16
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Yengo CM, De La Cruz EM, Chrin LR, Gaffney DP, Berger CL. Actin-induced closure of the actin-binding cleft of smooth muscle myosin. J Biol Chem 2002; 277:24114-9. [PMID: 11959853 DOI: 10.1074/jbc.m111253200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The putative actin-binding interface of myosin is separated by a large cleft that extends into the base of the nucleotide binding pocket, suggesting that it may be important for mediating the nucleotide-dependent changes in the affinity for myosin on actin. We have genetically engineered a truncated version of smooth muscle myosin containing the motor domain and the essential light chain-binding region (MDE), with a single tryptophan residue at position 425 (F425W-MDE) in the actin-binding cleft. Steady-state fluorescence of F425W-MDE demonstrates that Trp-425 is in a more solvent-exposed conformation in the presence of MgATP than in the presence of MgADP or absence of nucleotide, consistent with closure of the actin-binding cleft in the strongly bound states of MgATPase cycle for myosin. Transient kinetic experiments demonstrate a direct correlation between the rates of strong actin binding and the conformation of Trp-425 in the actin-binding cleft, and suggest the existence of a novel conformation of myosin not previously seen in solution or by x-ray crystallography. Thus, these results directly demonstrate that: 1) the conformation of the actin-binding cleft mediates the affinity of myosin for actin in a nucleotide-dependent manner, and 2) actin induces conformational changes in myosin required to generate force and motion during muscle contraction.
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Affiliation(s)
- Christopher M Yengo
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, Vermont 05405-0075, USA
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17
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Kollmar M, Dürrwang U, Kliche W, Manstein DJ, Kull FJ. Crystal structure of the motor domain of a class-I myosin. EMBO J 2002; 21:2517-25. [PMID: 12032065 PMCID: PMC126035 DOI: 10.1093/emboj/21.11.2517] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The crystal structure of the motor domain of Dictyostelium discoideum myosin-IE, a monomeric unconventional myosin, was determined. The crystallographic asymmetric unit contains four independently resolved molecules, highlighting regions that undergo large conformational changes. Differences are particularly pronounced in the actin binding region and the converter domain. The changes in position of the converter domain reflect movements both parallel to and perpendicular to the actin axis. The orientation of the converter domain is approximately 30 degrees further up than in other myosin structures, indicating that MyoE can produce a larger power stroke by rotating its lever arm through a larger angle. The role of extended loops near the actin-binding site is discussed in the context of cellular localization. The core regions of the motor domain are similar, and the structure reveals how that core is stabilized in the absence of an N-terminal SH3-like domain.
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Affiliation(s)
- Martin Kollmar
- Department of Biophysics, Max Planck Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Germany
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18
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Shutova T, Deikus G, Irrgang KD, Klimov VV, Renger G. Origin and properties of fluorescence emission from the extrinsic 33 kDa manganese stabilizing protein of higher plant water oxidizing complex. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1504:371-8. [PMID: 11245801 DOI: 10.1016/s0005-2728(00)00267-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fluorescence properties of the isolated extrinsic 33 kDa subunit acting as 'manganese stabilizing protein' (MSP) of the water oxidizing complex in photosynthesis was analyzed in buffer solution. Measurements of the emission spectra as a function of excitation wavelength, pH and temperature led to the following results: (a) under all experimental conditions the spectra monitored were found to be the composite of two contributions referred to as '306 nm band' and 'long-wavelength band', (b) the excitation spectra of these two bands closely resemble those of tyrosine and tryptophan in solution, respectively, (c) the spectral shape of the '306 nm band' is virtually independent on pH but its amplitude drastically decreases in the alkaline with a pK of 11.7, (d) the amplitude of the 'long-wavelength' emission band at alkaline pH slightly increases when the pH rises from 7.2 to about 11.3 followed by a sharp decline at higher pH, and (e) the shape of the overall spectrum at pH 7.2 is only slightly changed upon heating to 90 degrees C whereas the amplitude significantly declines. Based on these findings the two distinct fluorescence bands are ascribed to tyrosine(s) ('306 nm band') and the only tryptophan residue W241 of MSP from higher plants ('long-wavelength band') as emitters which are both embedded into a rather hydrophobic environment.
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Affiliation(s)
- T Shutova
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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19
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Abstract
High-resolution structures of the motor domain of myosin II and lower resolution actin-myosin structures have led to the "swinging lever arm" model for myosin force generation. The available kinetic data are not all easily reconciled with this model and understanding the final details of the myosin motor mechanism must await actin-myosin co-crystals. The observation that myosin can populate multiple states in the absence of actin has nonetheless led to significant insights. The currently known myosin structures correspond to defined kinetic states that bind weakly (K(d)>microM) to actin. It is possible that the myosin lever arm could complete its swing before strong binding to actin and force generation--a process that would correspond, in the absence of load, to a Brownian ratchet. We further suggest that, under load, internal springs within the myosin head could decouple force generation and lever arm movement.
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Affiliation(s)
- A Houdusse
- Structural Motility, Institut Curie CNRS, UMR 144, 26 rue d'Ulm, 75248 05 Paris Cedex, France.
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Abstract
Actin contains four tryptophan residues, W79, W86, W340, and W356, all located in subdomain 1 of the protein. Replacement of each of these residues with either tyrosine (W79Y and W356Y) or phenylalanine (W86F and W340F) generated viable proteins in the yeast Saccharomyces cerevisiae, which, when purified, allowed the analysis of the contribution of these residues to the overall tryptophan fluorescence of actin. The sum of the relative contributions of these tryptophans was found to account for the intrinsic fluorescence of wild-type actin, indicating that energy transfer between the tryptophans is not the main determinant of their quantum yield, and that these mutations induce little conformational change to the protein. This was borne out by virtually identical polymerization rates and similar myosin interactions of each of the mutants and the wild-type actin. In addition, these mutants allowed the dissection of the microenvironment of each tryptophan as actin undergoes conformational changes upon metal cation exchange and polymerization. Based on the relative tryptophan contributions determined from single mutants, a triple mutant of yeast actin (W79) was generated that showed small intrinsic fluorescence and should be useful for studies of actin interactions with actin-binding proteins.
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Affiliation(s)
- T C Doyle
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095, USA
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21
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The Chemistry of Movement. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50022-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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22
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Ullrich B, Laberge M, Tölgyesi F, Szeltner Z, Polgár L, Fidy J. Trp42 rotamers report reduced flexibility when the inhibitor acetyl-pepstatin is bound to HIV-1 protease. Protein Sci 2000; 9:2232-45. [PMID: 11152134 PMCID: PMC2144495 DOI: 10.1110/ps.9.11.2232] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The Q7K/L331/L631 HIV-1 protease mutant was expressed in Escherichia coli and the effect of binding a substrate-analog inhibitor, acetyl-pepstatin, was investigated by fluorescence spectroscopy and molecular dynamics. The dimeric enzyme has four intrinsic tryptophans, located at positions 6 and 42 in each monomer. Fluorescence spectra and acrylamide quenching experiments show two differently accessible Trp populations in the apoenzyme with k(q1) = 6.85 x 10(9) M(-1) s(-1) and k(q2) = 1.88 x 10(9) M(-1) s(-1), that merge into one in the complex with k(q) = 1.78 x 10(9) M(-1) s(-1). 500 ps trajectory analysis of Trp X1/X2 rotameric interconversions suggest a model to account for the observed Trp fluorescence. In the simulations, Trp6/Trp6B rotameric interconversions do not occur on this timescale for both HIV forms. In the apoenzyme simulations, however, both Trp42s and Trp42Bs are flipping between X1/X2 states; in the complexed form, no such interconverions occur. A detailed investigation of the local Trp environments sampled during the molecular dynamics simulation suggests that one of the apoenzyme Trp42B rotameric interconversions would allow indole-quencher contact, such as with nearby Tyr59. This could account for the short lifetime component. The model thus interprets the experimental data on the basis of the conformational fluctuations of Trp42s alone. It suggests that the rotameric interconversions of these Trps, located relatively far from the active site and at the very start of the flap region, becomes restrained when the apoenzyme binds the inhibitor. The model is thus consistent with associating components of the fluorescence decay in HIV-1 protease to ground state conformational heterogeneity.
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Affiliation(s)
- B Ullrich
- Institute of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
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Yamashita H, Tyska MJ, Warshaw DM, Lowey S, Trybus KM. Functional consequences of mutations in the smooth muscle myosin heavy chain at sites implicated in familial hypertrophic cardiomyopathy. J Biol Chem 2000; 275:28045-52. [PMID: 10882745 DOI: 10.1074/jbc.m005485200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Familial hypertrophic cardiomyopathy (FHC) is frequently associated with mutations in the beta-cardiac myosin heavy chain. Many of the implicated residues are located in highly conserved regions of the myosin II class, suggesting that these mutations may impair the basic functions of the molecular motor. To test this hypothesis, we have prepared recombinant smooth muscle heavy meromyosin with mutations at sites homologous to those associated with FHC by using a baculovirus/insect cell expression system. Several of the heavy meromyosin mutants, in particular R403Q, showed an increase in actin filament velocity in a motility assay and an enhanced actin-activated ATPase activity. Single molecule mechanics, using a laser trap, gave unitary displacements and forces for the mutants that were similar to wild type, but the attachment times to actin following a unitary displacement were markedly reduced. These results suggest that the increases in activity are due to a change in kinetics and not due to a change in the intrinsic mechanical properties of the motor. In contrast to earlier reports, we find that mutations in residues implicated in FHC affect motor function by enhancing myosin activity rather than by a loss of function.
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MESH Headings
- Actins/metabolism
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Binding Sites
- Cardiomyopathy, Hypertrophic/genetics
- Cardiomyopathy, Hypertrophic/metabolism
- Chickens
- Conserved Sequence
- Crystallography, X-Ray
- Gizzard, Avian
- Humans
- Kinetics
- Models, Molecular
- Muscle, Smooth/metabolism
- Muscle, Smooth, Vascular/metabolism
- Mutagenesis, Site-Directed
- Myocardium/metabolism
- Myosin Heavy Chains/chemistry
- Myosin Heavy Chains/genetics
- Myosin Heavy Chains/metabolism
- Myosins/chemistry
- Myosins/genetics
- Myosins/metabolism
- Point Mutation
- Protein Conformation
- Protein Structure, Secondary
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Affiliation(s)
- H Yamashita
- Department of Cardiovascular Medicine, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan
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24
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Yengo CM, Chrin LR, Berger CL. Interaction of myosin LYS-553 with the C-terminus and DNase I-binding loop of actin examined by fluorescence resonance energy transfer. J Struct Biol 2000; 131:187-96. [PMID: 11052891 DOI: 10.1006/jsbi.2000.4296] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fluorescence resonance energy transfer (FRET) experiments were carried out in the absence of nucleotide (rigor) or in the presence of MgADP between fluorescent donor probes (IAEDANS (5((((2-iodoacetyl)amino)ethyl)amino)-naphthalene-1-sulfonic acid) at Cys-374 or DANSYL (5-dimethylamino naphthalene-1-(N-(5-aminopentyl))sulfonamide) at Gln-41 of actin and acceptor molecules (FHS (6-[fluorescein-5(and 6)-carboxamido] hexanoic acid succinimidyl ester) at Lys-553 of skeletal muscle myosin subfragment 1. The critical Förster distance (R(0)) was determined to be 44 and 38 A for the IAEDANS-FHS and DANSYL-FHS donor-acceptor pairs, respectively. The efficiency of energy transfer between the acceptor molecules at Lys-553 of myosin and donor probes at Cys-374 or Gln-41 of actin was calculated to be 0.78 +/- 0.01 or 0.94 +/- 0.01, respectively, corresponding to distances of 35.6 +/- 0.4 A and 24.0 +/- 1.6 A, respectively. MgADP had no significant effect on the distances observed in rigor. Thus, rearrangements in the acto-myosin interface are likely to occur elsewhere than in the lower 50-kDa subdomain of myosin as its affinity for actin is weakened by MgADP binding.
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Affiliation(s)
- C M Yengo
- Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA
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25
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MacLean JJ, Chrin LR, Berger CL. Dynamics at Lys-553 of the acto-myosin interface in the weakly and strongly bound states. Biophys J 2000; 78:1441-8. [PMID: 10692329 PMCID: PMC1300742 DOI: 10.1016/s0006-3495(00)76697-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Lys-553 of skeletal muscle myosin subfragment 1 (S1) was specifically labeled with the fluorescent probe FHS (6-[fluorescein-5(and 6)-carboxamido]hexanoic acid succinimidyl ester) and fluorescence quenching experiments were carried out to determine the accessibility of this probe at Lys-553 in both the strongly and weakly actin-bound states of the MgATPase cycle. Solvent quenchers of varying charge [nitromethane, (2,2,6, 6-tetramethyl-1-piperinyloxy) (TEMPO), iodide (I(-)), and thallium (Tl(+))] were used to assess both the steric and electrostatic accessibilities of the FHS probe at Lys-553. In the strongly bound rigor (nucleotide-free) and MgADP states, actin offered no protection from solvent quenching of FHS by nitromethane, TEMPO, or thallium, but did decrease the Stern-Volmer constant by almost a factor of two when iodide was used as the quencher. The protection from iodide quenching was almost fully reversed with the addition of 150 mM KCl, suggesting this effect is ionic in nature rather than steric. Conversely, actin offered no protection from iodide quenching at low ionic strength during steady-state ATP hydrolysis, even with a significant fraction of the myosin heads bound to actin. Thus, the lower 50 kD subdomain of myosin containing Lys-553 appears to interact differently with actin in the weakly and strongly bound states.
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Affiliation(s)
- J J MacLean
- Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA
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Cooper WC, Chrin LR, Berger CL. Detection of fluorescently labeled actin-bound cross-bridges in actively contracting myofibrils. Biophys J 2000; 78:1449-57. [PMID: 10692330 PMCID: PMC1300743 DOI: 10.1016/s0006-3495(00)76698-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Myosin subfragment 1 (S1) can be specifically modified at Lys-553 with the fluorescent probe FHS (6-[fluorescein-5(and 6)-carboxamido]hexanoic acid succinimidyl ester) (Bertrand, R., J. Derancourt, and R. Kassab. 1995. Biochemistry. 34:9500-9507), and solvent quenching of FHS-S1 with iodide has been shown to be sensitive to actin binding at low ionic strength (MacLean, Chrin, and Berger, 2000. Biophys. J. 000-000). In order to extend these results and examine the fraction of actin-bound myosin heads within the myofilament lattice during calcium activation, we have modified skeletal muscle myofibrils, mildly cross-linked with EDC (1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide) to prevent shortening, with FHS. The myosin heavy chain appears to be the predominant site of labeling, and the iodide quenching patterns are consistent with those obtained for myosin S1 in solution, suggesting that Lys-553 is indeed the primary site of FHS incorporation in skeletal muscle myofibrils. The iodide quenching results from calcium-activated FHS-myofibrils indicate that during isometric contraction 29% of the myosin heads are strongly bound to actin within the myofilament lattice at low ionic strength. These results suggest that myosin can be specifically modified with FHS in more complex and physiologically relevant preparations, allowing the real time examination of cross-bridge interactions with actin in in vitro motility assays and during isometric and isotonic contractions within single muscle fibers.
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Affiliation(s)
- W C Cooper
- Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA
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27
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Abstract
The crystal structures of smooth muscle and scallop striated muscle myosin have both been completed in the past 18 months. Structural studies of unconventional myosins, in particular the stunning discovery that myosin VI moves backwards on actin, are starting to have deep impact on the field and have induced new ways of thinking about actin-based motility. Sophisticated genetic, biochemical and biophysical studies were used to test and refine hypotheses of the molecular mechanism of motility that were developed in the past. Although all these studies confirmed some aspects of these hypotheses, they also raised many new unresolved questions. Much of the evidence points to the importance of the actin-myosin binding process and an associated disorder-to-order transition.
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Affiliation(s)
- N Volkmann
- The Burnham Institute, La Jolla, 92037, USA.
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