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Szikora S, Görög P, Mihály J. The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:5306. [PMID: 35628117 PMCID: PMC9140763 DOI: 10.3390/ijms23105306] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
The actin containing tropomyosin and troponin decorated thin filaments form one of the crucial components of the contractile apparatus in muscles. The thin filaments are organized into densely packed lattices interdigitated with myosin-based thick filaments. The crossbridge interactions between these myofilaments drive muscle contraction, and the degree of myofilament overlap is a key factor of contractile force determination. As such, the optimal length of the thin filaments is critical for efficient activity, therefore, this parameter is precisely controlled according to the workload of a given muscle. Thin filament length is thought to be regulated by two major, but only partially understood mechanisms: it is set by (i) factors that mediate the assembly of filaments from monomers and catalyze their elongation, and (ii) by factors that specify their length and uniformity. Mutations affecting these factors can alter the length of thin filaments, and in human cases, many of them are linked to debilitating diseases such as nemaline myopathy and dilated cardiomyopathy.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
| | - Péter Görög
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Doctoral School of Multidisciplinary Medical Science, Faculty of Medicine, University of Szeged, H-6725 Szeged, Hungary
| | - József Mihály
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Department of Genetics, University of Szeged, H-6726 Szeged, Hungary
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Daneshparvar N, Taylor DW, O'Leary TS, Rahmani H, Abbasiyeganeh F, Previs MJ, Taylor KA. CryoEM structure of Drosophila flight muscle thick filaments at 7 Å resolution. Life Sci Alliance 2020; 3:3/8/e202000823. [PMID: 32718994 PMCID: PMC7391215 DOI: 10.26508/lsa.202000823] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 06/30/2020] [Accepted: 06/30/2020] [Indexed: 11/24/2022] Open
Abstract
Striated muscle thick filaments are composed of myosin II and several non-myosin proteins. Myosin II's long α-helical coiled-coil tail forms the dense protein backbone of filaments, whereas its N-terminal globular head containing the catalytic and actin-binding activities extends outward from the backbone. Here, we report the structure of thick filaments of the flight muscle of the fruit fly Drosophila melanogaster at 7 Å resolution. Its myosin tails are arranged in curved molecular crystalline layers identical to flight muscles of the giant water bug Lethocerus indicus Four non-myosin densities are observed, three of which correspond to ones found in Lethocerus; one new density, possibly stretchin-mlck, is found on the backbone outer surface. Surprisingly, the myosin heads are disordered rather than ordered along the filament backbone. Our results show striking myosin tail similarity within flight muscle filaments of two insect orders separated by several hundred million years of evolution.
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Affiliation(s)
- Nadia Daneshparvar
- Department of Physics, Florida State University, Tallahassee, FL, USA.,Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, USA
| | - Dianne W Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, USA
| | - Thomas S O'Leary
- Department of Molecular Physiology & Biophysics, University of Vermont College of Medicine, Burlington, VT, USA
| | - Hamidreza Rahmani
- Department of Physics, Florida State University, Tallahassee, FL, USA.,Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, USA
| | | | - Michael J Previs
- Department of Molecular Physiology & Biophysics, University of Vermont College of Medicine, Burlington, VT, USA
| | - Kenneth A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, USA
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3
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Szikora S, Gajdos T, Novák T, Farkas D, Földi I, Lenart P, Erdélyi M, Mihály J. Nanoscopy reveals the layered organization of the sarcomeric H-zone and I-band complexes. J Cell Biol 2020; 219:132617. [PMID: 31816054 PMCID: PMC7039190 DOI: 10.1083/jcb.201907026] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/04/2019] [Accepted: 10/22/2019] [Indexed: 01/18/2023] Open
Abstract
Sarcomeres are extremely highly ordered macromolecular assemblies where structural organization is intimately linked to their functionality as contractile units. Although the structural basis of actin and Myosin interaction is revealed at a quasiatomic resolution, much less is known about the molecular organization of the I-band and H-zone. We report the development of a powerful nanoscopic approach, combined with a structure-averaging algorithm, that allowed us to determine the position of 27 sarcomeric proteins in Drosophila melanogaster flight muscles with a quasimolecular, ∼5- to 10-nm localization precision. With this protein localization atlas and template-based protein structure modeling, we have assembled refined I-band and H-zone models with unparalleled scope and resolution. In addition, we found that actin regulatory proteins of the H-zone are organized into two distinct layers, suggesting that the major place of thin filament assembly is an M-line-centered narrow domain where short actin oligomers can form and subsequently anneal to the pointed end.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Tamás Gajdos
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Tibor Novák
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Dávid Farkas
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary.,Doctoral School in Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - István Földi
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Peter Lenart
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Miklós Erdélyi
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - József Mihály
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
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4
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Through thick and thin: dual regulation of insect flight muscle and cardiac muscle compared. J Muscle Res Cell Motil 2019; 40:99-110. [PMID: 31292801 PMCID: PMC6726838 DOI: 10.1007/s10974-019-09536-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 07/02/2019] [Indexed: 01/15/2023]
Abstract
Both insect flight muscle and cardiac muscle contract rhythmically, but the way in which repetitive contractions are controlled is different in the two types of muscle. We have compared the flight muscle of the water bug, Lethocerus, with cardiac muscle. Both have relatively high resting elasticity and are activated by an increase in sarcomere length or a quick stretch. The larger response of flight muscle is attributed to the highly ordered lattice of thick and thin filaments and to an isoform of troponin C that has no exchangeable Ca2+-binding site. The Ca2+ sensitivity of cardiac muscle and flight muscle can be manipulated so that cardiac muscle responds to Ca2+ like flight muscle, and flight muscle responds like cardiac muscle, showing the malleability of regulation. The interactions of the subunits in flight muscle troponin are described; a model of the complex, using the structure of cardiac troponin as a template, shows an overall similarity of cardiac and flight muscle troponin complexes. The dual regulation by thick and thin filaments in skeletal and cardiac muscle is thought to operate in flight muscle. The structure of inhibited myosin heads folded back on the thick filament in relaxed Lethocerus fibres has not been seen in other species and may be an adaptation to the rapid contractions of flight muscle. A scheme for regulation by thick and thin filaments during oscillatory contraction is described. Cardiac and flight muscle have much in common, but the differing mechanical requirements mean that regulation by both thick and thin filaments is adapted to the particular muscle.
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Taylor KA, Rahmani H, Edwards RJ, Reedy MK. Insights into Actin-Myosin Interactions within Muscle from 3D Electron Microscopy. Int J Mol Sci 2019; 20:ijms20071703. [PMID: 30959804 PMCID: PMC6479483 DOI: 10.3390/ijms20071703] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/31/2019] [Accepted: 04/01/2019] [Indexed: 01/12/2023] Open
Abstract
Much has been learned about the interaction between myosin and actin through biochemistry, in vitro motility assays and cryo-electron microscopy (cryoEM) of F-actin, decorated with myosin heads. Comparatively less is known about actin-myosin interactions within the filament lattice of muscle, where myosin heads function as independent force generators and thus most measurements report an average signal from multiple biochemical and mechanical states. All of the 3D imaging by electron microscopy (EM) that has revealed the interplay of the regular array of actin subunits and myosin heads within the filament lattice has been accomplished using the flight muscle of the large water bug Lethocerus sp. The Lethocerus flight muscle possesses a particularly favorable filament arrangement that enables all the myosin cross-bridges contacting the actin filament to be visualized in a thin section. This review covers the history of this effort and the progress toward visualizing the complex set of conformational changes that myosin heads make when binding to actin in several static states, as well as the fast frozen actively contracting muscle. The efforts have revealed a consistent pattern of changes to the myosin head structures as determined by X-ray crystallography needed to explain the structure of the different actomyosin interactions observed in situ.
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Affiliation(s)
- Kenneth A Taylor
- Florida State University, Institute of Molecular Biophysics, Tallahassee, FL 32306-4380, USA.
| | - Hamidreza Rahmani
- Florida State University, Institute of Molecular Biophysics, Tallahassee, FL 32306-4380, USA.
| | - Robert J Edwards
- Duke University Medical Center, Department of Cell Biology, Durham, NC 27607, USA.
| | - Michael K Reedy
- Duke University Medical Center, Department of Cell Biology, Durham, NC 27607, USA.
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Hu Z, Taylor DW, Reedy MK, Edwards RJ, Taylor KA. Structure of myosin filaments from relaxed Lethocerus flight muscle by cryo-EM at 6 Å resolution. SCIENCE ADVANCES 2016; 2:e1600058. [PMID: 27704041 PMCID: PMC5045269 DOI: 10.1126/sciadv.1600058] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 08/23/2016] [Indexed: 05/09/2023]
Abstract
We describe a cryo-electron microscopy three-dimensional image reconstruction of relaxed myosin II-containing thick filaments from the flight muscle of the giant water bug Lethocerus indicus. The relaxed thick filament structure is a key element of muscle physiology because it facilitates the reextension process following contraction. Conversely, the myosin heads must disrupt their relaxed arrangement to drive contraction. Previous models predicted that Lethocerus myosin was unique in having an intermolecular head-head interaction, as opposed to the intramolecular head-head interaction observed in all other species. In contrast to the predicted model, we find an intramolecular head-head interaction, which is similar to that of other thick filaments but oriented in a distinctly different way. The arrangement of myosin's long α-helical coiled-coil rod domain has been hypothesized as either curved layers or helical subfilaments. Our reconstruction is the first report having sufficient resolution to track the rod α helices in their native environment at resolutions ~5.5 Å, and it shows that the layer arrangement is correct for Lethocerus. Threading separate paths through the forest of myosin coiled coils are four nonmyosin peptides. We suggest that the unusual position of the heads and the rod arrangement separated by nonmyosin peptides are adaptations for mechanical signal transduction whereby applied tension disrupts the myosin heads as a component of stretch activation.
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Affiliation(s)
- Zhongjun Hu
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306–4380, USA
| | - Dianne W. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306–4380, USA
| | - Michael K. Reedy
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27607, USA
| | - Robert J. Edwards
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27607, USA
| | - Kenneth A. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306–4380, USA
- Corresponding author.
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Wang Q, Newhard CS, Ramanath S, Sheppard D, Swank DM. An embryonic myosin converter domain influences Drosophila indirect flight muscle stretch activation, power generation and flight. ACTA ACUST UNITED AC 2013; 217:290-8. [PMID: 24115062 DOI: 10.1242/jeb.091769] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stretch activation (SA) is critical to the flight ability of insects powered by asynchronous, indirect flight muscles (IFMs). An essential muscle protein component for SA and power generation is myosin. Which structural domains of myosin are significant for setting SA properties and power generation levels is poorly understood. We made use of the transgenic techniques and unique single muscle myosin heavy chain gene of Drosophila to test the influence of the myosin converter domain on IFM SA and power generation. Replacing the endogenous converter with an embryonic version decreased SA tension and the rate of SA tension generation. The alterations in SA properties and myosin kinetics from the converter exchange caused power generation to drop to 10% of control fiber power when the optimal conditions for control fibers - 1% muscle length (ML) amplitude and 150 Hz oscillation frequency - were applied to fibers expressing the embryonic converter (IFI-EC). Optimizing conditions for IFI-EC fiber power production, by doubling ML amplitude and decreasing oscillation frequency by 60%, improved power output to 60% of optimized control fiber power. IFI-EC flies altered their aerodynamic flight characteristics to better match optimal fiber power generation conditions as wing beat frequency decreased and wing stroke amplitude increased. This enabled flight in spite of the drastic changes to fiber mechanical performance.
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Affiliation(s)
- Qian Wang
- Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA
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Craig R. Isolation, electron microscopy and 3D reconstruction of invertebrate muscle myofilaments. Methods 2011; 56:33-43. [PMID: 22155190 DOI: 10.1016/j.ymeth.2011.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/22/2011] [Accepted: 11/26/2011] [Indexed: 10/14/2022] Open
Abstract
Understanding the molecular mechanism of muscle contraction and its regulation has been greatly influenced and aided by studies of myofilament structure in invertebrate muscles. Invertebrates are easily obtained and cover a broad spectrum of species and functional specializations. The thick (myosin-containing) filaments from some invertebrates are especially stable and simple in structure and thus much more amenable to structural analysis than those of vertebrates. Comparative studies of invertebrate filaments by electron microscopy and image processing have provided important generalizations of muscle molecular structure and function. This article reviews methods for preparing thick and thin filaments from invertebrate muscle, for imaging filaments by electron microscopy, and for determining their three dimensional structure by image processing. It also highlights some of the key insights into filament function that have come from these studies.
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Affiliation(s)
- Roger Craig
- Department of Cell Biology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
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9
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Regulating the contraction of insect flight muscle. J Muscle Res Cell Motil 2011; 32:303-13. [PMID: 22105701 DOI: 10.1007/s10974-011-9278-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Accepted: 11/11/2011] [Indexed: 10/15/2022]
Abstract
The rapid movement of the wings in small insects is powered by the indirect flight muscles. These muscles are capable of contracting at up to 1,000 Hz because they are activated mechanically by stretching. The mechanism is so efficient that it is also used in larger insects like the waterbug, Lethocerus. The oscillatory activity of the muscles occurs a low concentration of Ca(2+), which stays constant as the muscles contract and relax. Activation by stretch requires particular isoforms of tropomyosin and the troponin complex on the thin filament. We compare the tropomyosin and troponin of Lethocerus and Drosophila with that of vertebrates. The characteristics of the flight muscle regulatory proteins suggest ways in which stretch-activation works. There is evidence for bridges between troponin on thin filaments and myosin crossbridges on the thick filaments. Recent X-ray fibre diffraction results suggest that a pull on the bridges activates the thin filament by shifting tropomyosin from a blocking position on actin. The troponin bridges are likely to contain extended sequences of tropomyosin or troponin I (TnI). Flight muscle has two isoforms of TnC with different Ca(2+)-binding properties: F1 TnC is needed for stretch-activation and F2 TnC for isometric contractions. In this review, we describe the structural changes in both isoforms on binding Ca(2+) and TnI, and discuss how the steric model of muscle regulation can apply to insect flight muscle.
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10
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X-ray diffraction evidence for myosin-troponin connections and tropomyosin movement during stretch activation of insect flight muscle. Proc Natl Acad Sci U S A 2010; 108:120-5. [PMID: 21148419 DOI: 10.1073/pnas.1014599107] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Stretch activation is important in the mechanical properties of vertebrate cardiac muscle and essential to the flight muscles of most insects. Despite decades of investigation, the underlying molecular mechanism of stretch activation is unknown. We investigated the role of recently observed connections between myosin and troponin, called "troponin bridges," by analyzing real-time X-ray diffraction "movies" from sinusoidally stretch-activated Lethocerus muscles. Observed changes in X-ray reflections arising from myosin heads, actin filaments, troponin, and tropomyosin were consistent with the hypothesis that troponin bridges are the key agent of mechanical signal transduction. The time-resolved sequence of molecular changes suggests a mechanism for stretch activation, in which troponin bridges mechanically tug tropomyosin aside to relieve tropomyosin's steric blocking of myosin-actin binding. This enables subsequent force production, with cross-bridge targeting further enhanced by stretch-induced lattice compression and thick-filament twisting. Similar linkages may operate in other muscle systems, such as mammalian cardiac muscle, where stretch activation is thought to aid in cardiac ejection.
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Krzic U, Rybin V, Leonard KR, Linke WA, Bullard B. Regulation of oscillatory contraction in insect flight muscle by troponin. J Mol Biol 2010; 397:110-8. [PMID: 20100491 DOI: 10.1016/j.jmb.2010.01.039] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 01/06/2010] [Accepted: 01/18/2010] [Indexed: 11/25/2022]
Abstract
Insect indirect flight muscle is activated by sinusoidal length change, which enables the muscle to work at high frequencies, and contracts isometrically in response to Ca(2+). Indirect flight muscle has two TnC isoforms: F1 binding a single Ca(2+) in the C-domain, and F2 binding Ca(2+) in the N- and C-domains. Fibres substituted with F1 produce delayed force in response to a single rapid stretch, and those with F2 produce isometric force in response to Ca(2+). We have studied the effect of TnC isoforms on oscillatory work. In native Lethocerus indicus fibres, oscillatory work was superimposed on a level of isometric force that depended on Ca(2+) concentration. Maximum work was produced at pCa 6.1; at higher concentrations, work decreased as isometric force increased. In fibres substituted with F1 alone, work continued to rise as Ca(2+) was increased up to pCa 4.7. Fibres substituted with various F1:F2 ratios produced maximal work at a ratio of 100:1 or 50:1; a higher proportion of F2 increased isometric force at the expense of oscillatory work. The F1:F2 ratio was 9.8:1 in native fibres, as measured by immunofluorescence, using isoform-specific antibodies. The small amount of F2 needed to restore work to levels obtained for the native fibre is likely to be due to the relative affinity of F1 and F2 for TnH, the Lethocerus homologue of TnI. Affinity of TnC isoforms for a TnI fragment of TnH was measured by isothermal titration calorimetry. The K(d) was 1.01 muM for F1 binding and 22.7 nM for F2. The higher affinity of F2 can be attributed to two TnH binding sites on F2 and a single site on F1. Stretch may be sensed by an extended C-terminal domain of TnH, resulting in reversible dissociation of the inhibitory sequence from actin during the oscillatory cycle.
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Affiliation(s)
- Uros Krzic
- EMBL, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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12
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Wu S, Liu J, Reedy MC, Winkler H, Reedy MK, Taylor KA. Methods for identifying and averaging variable molecular conformations in tomograms of actively contracting insect flight muscle. J Struct Biol 2009; 168:485-502. [PMID: 19698791 PMCID: PMC2805068 DOI: 10.1016/j.jsb.2009.08.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 08/12/2009] [Accepted: 08/15/2009] [Indexed: 11/26/2022]
Abstract
During active muscle contraction, tension is generated through many simultaneous, independent interactions between the molecular motor myosin and the actin filaments. The ensemble of myosin motors displays heterogeneous conformations reflecting different mechanochemical steps of the ATPase pathway. We used electron tomography of actively contracting insect flight muscle fast-frozen, freeze substituted, Araldite embedded, thin-sectioned and stained, to obtain 3D snapshots of the multiplicity of actin-attached myosin structures. We describe procedures for alignment of the repeating lattice of sub-volumes (38.7 nm cross-bridge repeats bounded by troponin) and multivariate data analysis to identify self-similar repeats for computing class averages. Improvements in alignment and classification of repeat sub-volumes reveals (for the first time in active muscle images) the helix of actin subunits in the thin filament and the troponin density with sufficient clarity that a quasiatomic model of the thin filament can be built into the class averages independent of the myosin cross-bridges. We show how quasiatomic model building can identify both strong and weak myosin attachments to actin. We evaluate the accuracy of image classification to enumerate the different types of actin-myosin attachments.
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Affiliation(s)
- Shenping Wu
- Institute of Molecular Biophysics, Florida State University, Florida 32306-4380, USA
| | - Jun Liu
- Institute of Molecular Biophysics, Florida State University, Florida 32306-4380, USA
| | - Mary C. Reedy
- Dept of Cell Biology, Duke University Medical Center, Durham, NC 27710 USA
| | - Hanspeter Winkler
- Institute of Molecular Biophysics, Florida State University, Florida 32306-4380, USA
| | - Michael K. Reedy
- Dept of Cell Biology, Duke University Medical Center, Durham, NC 27710 USA
| | - Kenneth A. Taylor
- Institute of Molecular Biophysics, Florida State University, Florida 32306-4380, USA
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Hooper SL, Hobbs KH, Thuma JB. Invertebrate muscles: thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle. Prog Neurobiol 2008; 86:72-127. [PMID: 18616971 PMCID: PMC2650078 DOI: 10.1016/j.pneurobio.2008.06.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 05/08/2008] [Accepted: 06/12/2008] [Indexed: 11/26/2022]
Abstract
This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vertebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca(++) binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.
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Affiliation(s)
- Scott L. Hooper
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
| | - Kevin H. Hobbs
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
| | - Jeffrey B. Thuma
- Neuroscience Program Department of Biological Sciences Ohio University Athens, OH 45701 614 593-0679 (voice) 614 593-0687 (FAX)
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14
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Affiliation(s)
- Kenneth A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA
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15
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Squire JM, Bekyarova T, Farman G, Gore D, Rajkumar G, Knupp C, Lucaveche C, Reedy MC, Reedy MK, Irving TC. The myosin filament superlattice in the flight muscles of flies: A-band lattice optimisation for stretch-activation? J Mol Biol 2006; 361:823-38. [PMID: 16887144 DOI: 10.1016/j.jmb.2006.06.072] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2006] [Revised: 06/29/2006] [Accepted: 06/29/2006] [Indexed: 11/28/2022]
Abstract
Low-angle X-ray diffraction patterns from relaxed fruitfly (Drosophila) flight muscle recorded on the BioCat beamline at the Argonne Advanced Photon Source (APS) show many features similar to such patterns from the "classic" insect flight muscle in Lethocerus, the giant water bug, but there is a characteristically different pattern of sampling of the myosin filament layer-lines, which indicates the presence of a superlattice of myosin filaments in the Drosophila A-band. We show from analysis of the structure factor for this lattice that the sampling pattern is exactly as expected if adjacent four-stranded myosin filaments, of repeat 116 nm, are axially shifted in the hexagonal A-band lattice by one-third of the 14.5 nm axial spacing between crowns of myosin heads. In addition, electron micrographs of Drosophila and other flies (e.g. the house fly (Musca) and the flesh fly (Sarcophaga)) combined with image processing confirm that the same A-band superlattice occurs in all of these flies; it may be a general property of the Diptera. The different A-band organisation in flies compared with Lethocerus, which operates at a much lower wing beat frequency (approximately 30 Hz) and requires a warm-up period, may be a way of optimising the myosin and actin filament geometry needed both for stretch activation at the higher wing beat frequencies (50 Hz to 1000 Hz) of flies and their need for a rapid escape response.
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Affiliation(s)
- John M Squire
- Biological Structure & Function Section, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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Squire JM, Al-Khayat HA, Knupp C, Luther PK. Molecular Architecture in Muscle Contractile Assemblies. ADVANCES IN PROTEIN CHEMISTRY 2005; 71:17-87. [PMID: 16230109 DOI: 10.1016/s0065-3233(04)71002-5] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- John M Squire
- Biological Structure and Function Section, Biomedical Sciences Division, Imperial College London, London SW7 2AZ, United Kindom
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Tregear RT, Reedy MC, Goldman YE, Taylor KA, Winkler H, Franzini-Armstrong C, Sasaki H, Lucaveche C, Reedy MK. Cross-bridge number, position, and angle in target zones of cryofixed isometrically active insect flight muscle. Biophys J 2004; 86:3009-19. [PMID: 15111415 PMCID: PMC1304167 DOI: 10.1016/s0006-3495(04)74350-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Electron micrographic tomograms of isometrically active insect flight muscle, freeze substituted after rapid freezing, show binding of single myosin heads at varying angles that is largely restricted to actin target zones every 38.7 nm. To quantify the parameters that govern this pattern, we measured the number and position of attached myosin heads by tracing cross-bridges through the three-dimensional tomogram from their origins on 14.5-nm-spaced shelves along the thick filament to their thin filament attachments in the target zones. The relationship between the probability of cross-bridge formation and axial offset between the shelf and target zone center was well fitted by a Gaussian distribution. One head of each myosin whose origin is close to an actin target zone forms a cross-bridge most of the time. The probability of cross-bridge formation remains high for myosin heads originating within 8 nm axially of the target zone center and is low outside 12 nm. We infer that most target zone cross-bridges are nearly perpendicular to the filaments (60% within 11 degrees ). The results suggest that in isometric contraction, most cross-bridges maintain tension near the beginning of their working stroke at angles near perpendicular to the filament axis. Moreover, in the absence of filament sliding, cross-bridges cannot change tilt angle while attached nor reach other target zones while detached, so may cycle repeatedly on and off the same actin target monomer.
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Affiliation(s)
- Richard T Tregear
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom.
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AL-Khayat HA, Hudson L, Reedy MK, Irving TC, Squire JM. Myosin head configuration in relaxed insect flight muscle: x-ray modeled resting cross-bridges in a pre-powerstroke state are poised for actin binding. Biophys J 2003; 85:1063-79. [PMID: 12885653 PMCID: PMC1303227 DOI: 10.1016/s0006-3495(03)74545-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2003] [Accepted: 04/14/2003] [Indexed: 10/21/2022] Open
Abstract
Low-angle x-ray diffraction patterns from relaxed insect flight muscle recorded on the BioCAT beamline at the Argonne APS have been modeled to 6.5 nm resolution (R-factor 9.7%, 65 reflections) using the known myosin head atomic coordinates, a hinge between the motor (catalytic) domain and the light chain-binding (neck) region (lever arm), together with a simulated annealing procedure. The best head conformation angles around the hinge gave a head shape that was close to that typical of relaxed M*ADP*Pi heads, a head shape never before demonstrated in intact muscle. The best packing constrained the eight heads per crown within a compact crown shelf projecting at approximately 90 degrees to the filament axis. The two heads of each myosin molecule assume nonequivalent positions, one head projecting outward while the other curves round the thick filament surface to nose against the proximal neck of the projecting head of the neighboring molecule. The projecting heads immediately suggest a possible cross-bridge cycle. The relaxed projecting head, oriented almost as needed for actin attachment, will attach, then release Pi followed by ADP, as the lever arm with a purely axial change in tilt drives approximately 10 nm of actin filament sliding on the way to the nucleotide-free limit of its working stroke. The overall arrangement appears well designed to support precision cycling for the myogenic oscillatory mode of contraction with its enhanced stretch-activation response used in flight by insects equipped with asynchronous fibrillar flight muscles.
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Affiliation(s)
- Hind A AL-Khayat
- Biological Structure and Function Section, Biomedical Sciences Division, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
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Squire JM, Al-Khayat HA, Harford JJ, Hudson L, Irving T, Knupp C, Reedy MK. Modelling muscle motor conformations using low-angle X-ray diffraction. ACTA ACUST UNITED AC 2003; 150:103-10. [PMID: 16468939 DOI: 10.1049/ip-nbt:20031094] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
New results on myosin head organization using analysis of low-angle X-ray diffraction patterns from relaxed insect flight muscle (IFM) from a giant waterbug, building on previous studies of myosin filaments in bony fish skeletal muscle (BFM), show that the information content of such low-angle diffraction patterns is very high despite the 'crystallographically low' resolution limit (65 A) of the spacings of the Bragg diffraction peaks being used. This high information content and high structural sensitivity arises because: (i) the atomic structures of the domains of the myosin head are known from protein crystallography; and (ii) myosin head action appears to consist mainly of pivoting between domains which themselves stay rather constant in structure, thus (iii) the intensity distribution among diffraction peaks in even the low resolution diffraction pattern is highly determined by the high-resolution distribution of atomically modelled domain mass. A single model was selected among 5000+ computer-generated variations as giving the best fit for the 65 reflections recorded within the selected resolution limit of 65 A. Clear evidence for a change in shape of the insect flight muscle myosin motor between the resting (probably like the pre-powerstroke) state and the rigor state (considered to mimic the end-of-powerstroke conformation) has been obtained. This illustrates the power of the low-angle X-ray diffraction method. The implications of these new results about myosin motor action during muscle contraction are discussed.
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Affiliation(s)
- J M Squire
- Imperial College London, Biological Structure & Function Section, Biomedical Sciences Division, Faculty of Medicine, London, UKIllinois Institute of Technology, BioCAT, Dept. Biological, Chemical and Physical Sciences, Chicago, USADuke University, Dept of Cell Biology, Durham, USA
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20
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Nyland LR, Maughan DW. Morphology and transverse stiffness of Drosophila myofibrils measured by atomic force microscopy. Biophys J 2000; 78:1490-7. [PMID: 10692334 PMCID: PMC1300747 DOI: 10.1016/s0006-3495(00)76702-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Atomic force microscopy was used to investigate the surface morphology and transverse stiffness of myofibrils from Drosophila indirect flight muscle exposed to different physiologic solutions. I- and A-bands were clearly observed, and thick filaments were resolved along the periphery of the myofibril. Interfilament spacings correlated well with estimates from previous x-ray diffraction studies. Transverse stiffness was measured by using a blunt tip to indent a small section of the myofibrillar surface in the region of myofilament overlap. At 10 nm indention, the effective transverse stiffness (K( perpendicular)) of myofibrils in rigor solution (ATP-free, pCa 4.5) was 10.3 +/- 5.0 pN nm(-1) (mean +/- SEM, n = 8); in activating solution (pCa 4.5), 5.9 +/- 3.1 pN nm(-1); and in relaxing solution (pCa 8), 4.4 +/- 2.0 pN nm(-1). The apparent transverse Young's modulus (E( perpendicular)) was 94 +/- 41 kPa in the rigor state and 40 +/- 17 kPa in the relaxed state. The value of E( perpendicular) for calcium-activated myofibrils (55 +/- 29 kPa) was approximately a tenth that of Young's modulus in the longitudinal direction, a difference that at least partly reflects the transverse flexibility of the myosin molecule.
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Affiliation(s)
- L R Nyland
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405, USA
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van Straaten M, Goulding D, Kolmerer B, Labeit S, Clayton J, Leonard K, Bullard B. Association of kettin with actin in the Z-disc of insect flight muscle. J Mol Biol 1999; 285:1549-62. [PMID: 9917396 DOI: 10.1006/jmbi.1998.2386] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Z-discs of insect muscle contain kettin, a modular protein of 500-700 kDa. The Drosophila protein is made up of a chain of immunoglobulin (Ig) domains separated by linker sequences. Kettin differs from other modular muscle proteins of the Ig superfamily in binding to thin filaments rather than thick filaments. Kettin isolated from Lethocerus (waterbug) muscle is an elongated molecule 180 nm long, which binds to F-actin with high affinity (Kd=1.2 nM) and a stoichiometry of one Ig domain per actin protomer. Competition between kettin and tropomyosin for binding to actin excludes tropomyosin from the Z-disc. In contrast, kettin and alpha-actinin bind simultaneously to actin, which would reinforce the Z-disc lattice. In vitro, kettin promotes the antiparallel association of actin filaments, and a similar process may occur in the developing sarcomere: actin filaments interdigitate in an antiparallel fashion in the Z-disc with the N terminus of kettin within the Z-disc, and the C terminus some way outside. We propose a model for the association of kettin with actin in which the molecule follows the genetic helix of actin and Ig domains, separated by linker sequences, bind to each actin protomer.
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Affiliation(s)
- M van Straaten
- European Molecular Biology Laboratory, Heidelberg, 69012, Germany
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Ruiz T, Bullard B, Lepault J. Effects of calcium and nucleotides on the structure of insect flight muscle thin filaments. J Muscle Res Cell Motil 1998; 19:353-64. [PMID: 9635278 DOI: 10.1023/a:1005341502973] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The structure of the insect flight muscle thin filament has been studied using a Drosophila mutant (Ifm(2)2) which does not contain thick filaments. Thin filaments that are biochemically identical to those of the wild type can be isolated free from thick filament contamination. We show that isolated thin filaments have different symmetries depending upon the calcium concentration. While the filaments mainly contain 13 subunits in six turns of the 5.9 nm genetic helix in the absence of calcium, 50% of the filaments have 28 subunits in 13 turns of the genetic helix at calcium concentrations equivalent to those present during muscle contraction. We also show that the structure (mainly the helical order) of the thin filaments depends on the nature of the nucleotide bound to the actin monomers. Three-dimensional reconstructions of the thin filaments in the presence and absence of calcium show that tropomyosin moves between two different positions on the actin filament. However, in Drosophila the amplitude of the movement as well as the disorder in the positions of the components (tropomyosin, troponin complex) are larger than those generally observed in other species.
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Affiliation(s)
- T Ruiz
- Centre de Genetique Moleculaire, Centre National de la Recherche Scientifique, Gif sur Yvette, France
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Myosin Crossbridge Configurations in Equilibrium States of Vertebrate Skeletal Muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998. [DOI: 10.1007/978-1-4684-6039-1_35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Affiliation(s)
- T A Fassel
- Muscle Biology Laboratory, University of Wisconsin-Madison 53706, USA
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Abstract
A survey of skeletal muscles throughout craniates shows basic kinds of myosin filament arrangement, simple-lattice and superlattice, within the A-band of each sarcomere. Distribution of simple- and superlattice arrangements across a phylogeny of craniates suggests that the superlattice arrangement is primitive and that Amia and teleosts are derived in showing simple-lattice arrangements. Two taxa examined (Scyliorhinus and Acipenser) show both lattice types within the same organism implying that there is not a simple evolutionary transformation of one to the other fiber arrangement. We discuss the possible functional significance of the different lattice types. We believe that the crossbridges may have greater competition for actin binding sites in simple-lattice muscles compared to the superlattice types.
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Affiliation(s)
- P K Luther
- Blackett Laboratory, Imperial College, London, United Kingdom
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Winkler H, Taylor KA. Three-dimensional distortion correction applied to tomographic reconstructions of sectioned crystals. Ultramicroscopy 1996; 63:125-32. [PMID: 8875811 DOI: 10.1016/0304-3991(96)00024-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Unaveraged tomograms of embedded and sectioned insect flight muscle show not only structural variation within the individual unit cells but also defects in the filament lattice such as lack of straightness of the filaments and wrinkling of the sections. Adaptation of conventional 2D crystal image processing methods usually average out these structural variations and lattice defects thereby reducing the resolution and information content of the 3D reconstructions. We present here a computational method to correct the reconstructed 3D object for these distortions to make it suitable for further analysis. The correction is an extension of conventional 2D cross-correlation techniques applied to a 3D image. These procedures determine the unit cell positions of the distorted crystal and use a spline-fitting approach to calculate a mapping function from the observed positions that is subsequently used to reinterpolate the image onto a regular grid. The resulting reinterpolated image is corrected for both filament straightening as well as section wrinkling.
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Affiliation(s)
- H Winkler
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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