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Wu S, Liu J, Reedy MC, Tregear RT, Winkler H, Franzini-Armstrong C, Sasaki H, Lucaveche C, Goldman YE, Reedy MK, Taylor KA. Electron tomography of cryofixed, isometrically contracting insect flight muscle reveals novel actin-myosin interactions. PLoS One 2010; 5. [PMID: 20844746 PMCID: PMC2936580 DOI: 10.1371/journal.pone.0012643] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 07/29/2010] [Indexed: 11/18/2022] Open
Abstract
Background Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ. Methodology We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the “target zone”, situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77°/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127° range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening. Conclusion We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very different from strong binding attachments.
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Affiliation(s)
- Shenping Wu
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Jun Liu
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Mary C. Reedy
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Richard T. Tregear
- Medical Research Council Laboratory of Molecular Biology, Cambridge, England
| | - Hanspeter Winkler
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Clara Franzini-Armstrong
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Hiroyuki Sasaki
- Division of Fine Morphology, Core Research Facilities, Jikei University School of Medicine, Tokyo, Japan
| | - Carmen Lucaveche
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Yale E. Goldman
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Michael K. Reedy
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Kenneth A. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
- * E-mail:
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Haigh SE, Salvi SS, Sevdali M, Stark M, Goulding D, Clayton JD, Bullard B, Sparrow JC, Nongthomba U. Drosophila indirect flight muscle specific Act88F actin mutants as a model system for studying congenital myopathies of the human ACTA1 skeletal muscle actin gene. Neuromuscul Disord 2010; 20:363-74. [DOI: 10.1016/j.nmd.2010.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 02/01/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022]
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Grintsevich EE, Galkin VE, Orlova A, Ytterberg AJ, Mikati MM, Kudryashov DS, Loo JA, Egelman EH, Reisler E. Mapping of drebrin binding site on F-actin. J Mol Biol 2010; 398:542-54. [PMID: 20347847 DOI: 10.1016/j.jmb.2010.03.039] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 01/09/2023]
Abstract
Drebrin is a filament-binding protein involved in organizing the dendritic pool of actin. Previous in vivo studies identified the actin-binding domain of drebrin (DrABD), which causes the same rearrangements in the cytoskeleton as the full-length protein. Site-directed mutagenesis, electron microscopic reconstruction, and chemical cross-linking combined with mass spectrometry analysis were employed here to map the DrABD binding interface on actin filaments. DrABD could be simultaneously attached to two adjacent actin protomers using the combination of 2-iminothiolane (Traut's reagent) and MTS1 [1,1-methanediyl bis(methanethiosulfonate)]. Site-directed mutagenesis combined with chemical cross-linking revealed that residue 238 of DrABD is located within 5.4 A from C374 of actin protomer 1 and that native cysteine 308 of drebrin is near C374 of actin protomer 2. Mass spectrometry analysis revealed that a zero-length cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, can link the N-terminal G-S extension of the recombinant DrABD to E99 and/or E100 on actin. Efficient cross-linking of drebrin residues 238, 248, 252, 270, and 271 to actin residue 51 was achieved with reagents of different lengths (5.4-19 A). These results suggest that the "core" DrABD is centered on actin subdomain 2 and may adopt a folded conformation upon binding to F-actin. The results of electron microscopic reconstruction, which are in a good agreement with the cross-linking data, revealed polymorphism in DrABD binding to F-actin and suggested the existence of two binding sites. These results provide new structural insight into the previously observed competition between drebrin and several other F-actin-binding proteins.
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Affiliation(s)
- Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
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4
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Egelman EH. The iterative helical real space reconstruction method: surmounting the problems posed by real polymers. J Struct Biol 2007; 157:83-94. [PMID: 16919474 DOI: 10.1016/j.jsb.2006.05.015] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 05/02/2006] [Accepted: 05/16/2006] [Indexed: 11/20/2022]
Abstract
Many important biological macromolecules exist as helical polymers. Examples are actin, tubulin, myosin, RecA, Rad51, flagellin, pili, and filamentous bacteriophage. The first application of three-dimensional reconstruction from electron microscopic images was to a helical polymer, and a number of laboratories today are using helical tubes of integral membrane proteins for solving the structure of these proteins in the electron microscope at near atomic resolution. We have developed a method to analyze and reconstruct electron microscopic images of macromolecular helical polymers, the iterative helical real space reconstruction (IHRSR) algorithm. We can show that when there is disorder or heterogeneity, when the specimens diffract weakly, or when Bessel functions overlap, we can do far better with our method than can be done using traditional Fourier-Bessel approaches. In many cases, structures that were not even amenable to analysis can be solved at fairly high resolution using our method. The problems inherent in the traditional approach are discussed, and examples are presented illustrating how the IHRSR approach surmounts these problems.
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Affiliation(s)
- Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences, P.O. Box 800733, Charlottesville, VA 22908-0733, USA.
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5
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Abstract
This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.
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Affiliation(s)
- Scott L Hooper
- Neuroscience Program, Department of Biological Sciences, Irvine Hall, Ohio University, Athens, Ohio 45701, USA.
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6
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Trachtenberg S, Galkin VE, Egelman EH. Refining the structure of the Halobacterium salinarum flagellar filament using the iterative helical real space reconstruction method: insights into polymorphism. J Mol Biol 2005; 346:665-76. [PMID: 15713454 DOI: 10.1016/j.jmb.2004.12.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Revised: 11/30/2004] [Accepted: 12/07/2004] [Indexed: 11/20/2022]
Abstract
The eubacterial flagellar filament is an external, self-assembling, helical polymer approximately 220 A in diameter constructed from a highly conserved monomer, flagellin, which polymerizes externally at the distal end. The archaeal filament is only approximately 100 A in diameter, assembles at the proximal end and is constructed from different, glycosylated flagellins. Although the phenomenology of swimming is similar to that of eubacteria, the symmetry of the archebacterial filament is entirely different. Here, we extend our previous study on the flagellar coiled filament structure of strain R1M1 of Halobacterium salinarum. We use strain M175 of H.salinarum, which forms poly-flagellar bundles at high yield which, under conditions of relatively low ionic-strength (0.8 M versus 5 M) and low pH ( approximately 2.5 versus approximately 6.8), form straight filaments. We demonstrated previously that a single-particle approach to helical reconstruction has many advantages over conventional Fourier-Bessel methods when dealing with variable helical symmetry and heterogeneity. We show here that when this method is applied to the ordered helical structure of the archebacterial uncoiled flagellar filament, significant extensions in resolution can be obtained readily when compared to applying traditional helical techniques. The filament population can be separated into classes of different morphologies, which may represent polymorphic states. Using cryo-negatively stained images, a resolution of approximately 10-15 A has been achieved. Single alpha-helices can be fit into the reconstruction, supporting the proposed similarity of the structure to that of type IV bacterial pili.
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Affiliation(s)
- Shlomo Trachtenberg
- Department of Membrane and Ultrastructural Research, The Hebrew University of Jerusalem-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel.
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7
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Schmid MF, Sherman MB, Matsudaira P, Chiu W. Structure of the acrosomal bundle. Nature 2004; 431:104-7. [PMID: 15343340 DOI: 10.1038/nature02881] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Accepted: 07/20/2004] [Indexed: 11/08/2022]
Abstract
In the unactivated Limulus sperm, a 60- micro m-long bundle of actin filaments crosslinked by the protein scruin is bent and twisted into a coil around the base of the nucleus. At fertilization, the bundle uncoils and fully extends in five seconds to support a finger of membrane known as the acrosomal process. This biological spring is powered by stored elastic energy and does not require the action of motor proteins or actin polymerization. In a 9.5-A electron cryomicroscopic structure of the extended bundle, we show that twist, tilt and rotation of actin-scruin subunits deviate widely from a 'standard' F-actin filament. This variability in structural organization allows filaments to pack into a highly ordered and rigid bundle in the extended state and suggests a mechanism for storing and releasing energy between coiled and extended states without disassembly.
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Affiliation(s)
- Michael F Schmid
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Burgess S, Walker M, Knight PJ, Sparrow J, Schmitz S, Offer G, Bullard B, Leonard K, Holt J, Trinick J. Structural Studies of Arthrin: Monoubiquitinated Actin. J Mol Biol 2004; 341:1161-73. [PMID: 15321713 DOI: 10.1016/j.jmb.2004.06.077] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Revised: 06/07/2004] [Accepted: 06/10/2004] [Indexed: 11/17/2022]
Abstract
Here, we report on the structure and in situ location of arthrin (monoubiquitinated actin). Labelling of insect muscle thin filaments with a ubiquitin antibody reveals that every seventh subunit along the filament long-pitch helices is ubiquitinated. A three-dimensional reconstruction of frozen-hydrated arthrin filaments was produced. This was based on a novel algorithm that divides filament images into short segments that are used for single-particle image processing. Difference maps with an actin filament reconstruction locate ubiquitin at the side of actin sub-domain 1 opposite where myosin binds. Consistent with the reconstructions, peptide mapping places the ubiquitin linkage on lysine 118 in actin. Molecular modelling was used to generate arthrin monomers from ubiquitin and actin crystal structures. Filament models constructed from these monomers were compared with the arthrin reconstruction. The reconstruction suggests ubiquitin attached to Lys118 adopts one or a few conformers, stabilized by a small interface with actin. The function of actin ubiquitination is not known, but may involve regulation of muscle contractile activity.
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Affiliation(s)
- Stan Burgess
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
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Bajo AM, Prieto JC, Valenzuela P, Martínez P, Menor C, Marina A, Vázquez J, Guijarro LG. Association of adenylate cyclase with an actin-like protein in the human myometrium. Gynecol Endocrinol 2004; 18:89-96. [PMID: 15195500 DOI: 10.1080/09513590310001652964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Regulation of muscle contraction by second messengers such as cAMP and regulation of the adenylate cyclase enzyme by the cytoskeleton have been previously described. However, the physical association of both effector and structural elements is still unknown. In this context, we have co-purified a human myometrial adenylate cyclase with an actin-like protein in a two-step purification protocol. The adenylate cyclase catalytic unit was solubilized with Lubrol-PX, submitted to anionic exchange chromatography and purified about 7-fold. The eluate was applied to a forskolin-agarose column obtaining an adenylate cyclase extract enriched 257-fold (enzymatic activity of 1390 pmol/30 min per mg protein) that co-eluted with a 74.6-kDa protein that possessed the 18-27 amino-acid fragment from the N-terminal region of human actin. Under non-reducing conditions, the apparent molecular weight of this protein decreased to 54 kDa, which has been previously described for arthrin. These results provide the first demonstration of the physical association of human myometrial adenylate cyclase with a cytoskeleton-related protein, supporting the hypothesis that adenylate cyclase is regulated by mechanical stimuli.
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Affiliation(s)
- A M Bajo
- Department of Biochemistry and Molecular Biology, University of Alcalá, Alcalá de Henares, Spain
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VanLoock MS, Yu X, Yang S, Galkin VE, Huang H, Rajan SS, Anderson WF, Stohl EA, Seifert HS, Egelman EH. Complexes of RecA with LexA and RecX differentiate between active and inactive RecA nucleoprotein filaments. J Mol Biol 2003; 333:345-54. [PMID: 14529621 DOI: 10.1016/j.jmb.2003.08.053] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The bacterial RecA protein has been the dominant model system for understanding homologous genetic recombination. Although a crystal structure of RecA was solved ten years ago, we still do not have a detailed understanding of how the helical filament formed by RecA on DNA catalyzes the recognition of homology and the exchange of strands between two DNA molecules. Recent structural and spectroscopic studies have suggested that subunits in the helical filament formed in the RecA crystal are rotated when compared to the active RecA-ATP-DNA filament. We examine RecA-DNA-ATP filaments complexed with LexA and RecX to shed more light on the active RecA filament. The LexA repressor and RecX, an inhibitor of RecA, both bind within the deep helical groove of the RecA filament. Residues on RecA that interact with LexA cannot be explained by the crystal filament, but can be properly positioned in an existing model for the active filament. We show that the strand exchange activity of RecA, which can be inhibited when RecX is present at very low stoichiometry, is due to RecX forming a block across the deep helical groove of the RecA filament, where strand exchange occurs. It has previously been shown that changes in the nucleotide bound to RecA are associated with large motions of RecA's C-terminal domain. Since RecX binds from the C-terminal domain of one subunit to the nucleotide-binding core of another subunit, a stabilization of RecA's C-terminal domain by RecX can likely explain the inhibition of RecA's ATPase activity by RecX.
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Affiliation(s)
- Margaret S VanLoock
- Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Charlottesville, VA 22908-0733, USA
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Galkin VE, Orlova A, VanLoock MS, Egelman EH. Do the utrophin tandem calponin homology domains bind F-actin in a compact or extended conformation? J Mol Biol 2003; 331:967-72. [PMID: 12927533 DOI: 10.1016/s0022-2836(03)00842-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Tandem calponin-homology (CH) domains play an important role in the actin-binding function of many spectrin superfamily proteins. Crystal structures from several of these proteins have suggested a flexibility between these domains, and the manner in which these domains bind to F-actin has been the subject of some controversy. A recent paper has used electron microscopy and three-dimensional reconstruction to examine the complex of the utrophin tandem CH domain with F-actin. In contrast to our previously published study, a closed conformation of the two calponin-homology domains was suggested in the new work. We show here that the new results can be explained by incomplete binding of utrophin to actin, heterogeneity in the mode of binding, and angular disorder in F-actin. We conclude that helical averaging applied to disordered filaments is responsible for their results, and that approaches designed to separate out homogeneous subsets within such filamentous complexes offer many advantages.
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Affiliation(s)
- Vitold E Galkin
- Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Jordan Hill Box 800773, Charlottesville, VA 22908-0733, USA
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