Abstract
Azimuthal movement of tropomyosin around the F-actin thin filament is responsible for muscle activation and relaxation. Recently a model of αα-tropomyosin, derived from molecular-mechanics and electron microscopy of different contractile states, showed that tropomyosin is rather stiff and pre-bent to present one specific face to F-actin during azimuthal transitions. However, a new model based on cryo-EM of troponin- and myosin-free filaments proposes that the interacting-face of tropomyosin can differ significantly from that in the original model. Because resolution was insufficient to assign tropomyosin side-chains, the interacting-face could not be unambiguously determined. Here, we use structural analysis and energy landscapes to further examine the proposed models. The observed bend in seven crystal structures of tropomyosin is much closer in direction and extent to the original model than to the new model. Additionally, we computed the interaction map for repositioning tropomyosin over the F-actin surface, but now extended over a much larger surface than previously (using the original interacting-face). This map shows two energy minima—one corresponding to the “blocked-state” as in the original model, and the other related by a simple 24 Å translation of tropomyosin parallel to the F-actin axis. The tropomyosin-actin complex defined by the second minimum fits perfectly into the recent cryo-EM density, without requiring any change in the interacting-face. Together, these data suggest that movement of tropomyosin between regulatory states does not require interacting-face rotation. Further, they imply that thin filament assembly may involve an interplay between initially seeded tropomyosin molecules growing from distinct binding-site regions on actin.
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References
Behrmann E, Müller M, Penczek PA, Mannherz HG, Manstein DJ, Raunser S (2012) Structure of the rigor actin–tropomyosin–myosin complex. Cell 150:327–338
Brooks BR, Brooks CL, MacKerell AD, Nilsson L, Petrella RJ, Roux B et al (2009) CHARMM: the biomolecular simulation program. J Comput Chem 30:1545–1614
Brown JH, Kim KH, Jun G, Greenfield NJ, Dominguez R, Volkmann N, Hitchcock-DeGregori SE, Cohen C (2001) Deciphering the design of the tropomyosin molecule. Proc Natl Acad Sci USA 98:8496–8501
Brown JH, Zhou Z, Reshetnikova L, Robinson H, Yammani RD, Tobacman LS, Cohen C (2005) Structure of the mid-region of tropomyosin: bending and binding sites for actin. Proc Natl Acad Sci USA 102:18878–18883
Galińska-Rakoczy A, Engel P, Xu C, Jung H, Craig R, Tobacman LS, Lehman W (2008) Structural basis for the regulation of muscle contraction by troponin and tropomyosin. J Mol Biol 379:929–935
Gordon AM, Homsher E, Regnier M (2000) Regulation of contraction in striated muscle. Physiol Rev 80:853–924
Gunning PW, Hardeman EC, Lappalanien P, Mulvihill DP (2015) Tropomyosin—master regulator of actin filament function in the cytoskeleton. J Cell Sci (in press). doi:10.1242/jcs.172502
Hitchcock-DeGregori SE (2008) Tropomyosin: function follows form. Tropomyosin and the steric mechanism of muscle regulation. Adv Exp Med Biol 644:60–67
Holmes KC, Lehman W (2008) Gestalt-binding of tropomyosin to actin filaments. J Muscle Res Cell Motil 29:213–219
Humphrey W, Dalke A, Schulten K (1996) VMD: visual molecular dynamics. J Mol Graph 14:33–38
Hsiao JY, Goins LM, Petek NA, Mullins RD (2015) Arp2/3 complex and cofilin modulate binding of tropomyosin to branched actin filaments. Curr Biol 25:1573–1582
Johnson M, East DA, Mulvihill DP (2014) Formins determine the functional properties of actin filaments in yeast. Curr Biol 24:1525–1530
Lehman W, Craig R, Vibert P (1994) Ca2+-induced tropomyosin movement in Limulus thin filaments revealed by three- dimensional reconstruction. Nature 368:65–67
Lehman W, Galińska-Rakoczy A, Hatch V, Tobacman LS, Craig R (2009) Structural basis for the activation of muscle contraction by troponin and tropomyosin. J Mol Biol 388:673–681
Lehman W, Hatch V, Korman V, Rosol M, Thomas L, Maytum R, Geeves MA, Van Eyk JE, Tobacman LS, Craig R (2000) Tropomyosin and actin isoforms modulate the localization of tropomyosin strands on actin filaments. J Mol Biol 302:593–606
Lehman W, Orzechowski M, Li XE, Fischer S, Raunser S (2013) Gestalt-binding of tropomyosin on actin during thin filament activation. J Muscle Res Cell Motil 34:155–163
Li XE, Holmes KC, Lehman W, Jung H-S, Fischer S (2010) The shape and flexibility of tropomyosin coiled-coils: implications for actin filament assembly and regulation. J Mol Biol 395:327–399
Li XE, Tobacman LS, Mun JY, Craig R, Fischer S, Lehman W (2011) Tropomyosin position on F-actin revealed by EM reconstruction and computational chemistry. Biophys J 100:1005–1013
Li XE, Orzechowski M, Lehman W, Fischer S (2014) Structure and flexibility of the tropomyosin overlap junction. Biochem Biophys Res Commun 446:304–308
Li Y, Mui S, Brown JH, Strand J, Reshetnikova L, Tobacman LS, Cohen C (2002) The crystal structure of the C-terminal fragment of striated-muscle alpha-tropomyosin reveals a key troponin T recognition site. Proc Natl Acad Sci USA 99:7378–7383
Lorenz M, Poole KJV, Popp D, Rosenbaum G, Holmes KC (1995) An atomic model of the unregulated thin filament obtained by X-ray fiber diffraction on oriented actin-tropomyosin gels. J Mol Biol 246:108–119
Maytum R, Hatch V, Konrad M, Lehman W, Geeves MA (2008) Ultra short yeast tropomyosins show novel myosin regulation. J Biol Chem 283:1902–1910
McKillop DFA, Geeves MA (1993) Regulation of the interaction between actin and myosin subfragment-1: evidence for three states of the thin filament. Biophys J 65:693–701
Meshcheryakov VA, Krieger I, Kostyukova AS, Samatey FA (2011) Structure of a tropomyosin N-terminal fragment at 0.98 Å resolution. Acta Crystallogr D 67:822–825
Monteiro PB, Lataro RC, Ferro JA, Reinach Fde C (1994) Functional alpha-tropomyosin produced in Escherichia coli. A dipeptide extension can substitute the amino-terminal acetyl group. J Biol Chem 269:10461–10466
Nitanai Y, Minakata S, Maeda K, Oda N, Maéda Y (2007) Crystal structures of tropomyosin: flexible coiled-coil. Adv Exp Med Biol 592:137–151
Oda T, Iwasa M, Aihara T, Maéda Y, Narita A (2009) The nature of the globular- to fibrous-actin transition. Nature 457:441–445
Orzechowski M, Li XE, Fischer S, Lehman W (2014a) An atomic model of the tropomyosin cable on F-actin. Biophys J 107:694–699
Orzechowski M, Moore JR, Fischer S, Lehman W (2014b) Tropomyosin movement on F-actin during muscle activation explained by energy landscapes. Arch Biochem Biophys 545:63–68
Pettersen EF, Goddard TD, Huang CC, Couch GS, Greenblatt DM, Meng EC, Ferrin TE (2004) UCSF Chimera–a visualization system for exploratory research and analysis. J Comput Chem 25:1605–1612
Pirani A, Xu C, Hatch V, Craig R, Tobacman LS, Lehman W (2005) Single particle analysis of relaxed and activated muscle thin filaments. J Mol Biol 346:761–772
Poole KJ, Lorenz M, Evans G, Rosenbaum G, Pirani A, Tobacman LS, Lehman W, Holmes KC (2006) A comparison of muscle thin filament models obtained from electron microscopy reconstructions and low-angle X-ray fibre diagrams from non-overlap muscle. J Struct Biol 155:273–284
Potter JD, Gergely J (1974) Troponin, tropomyosin, and actin interactions in the Ca2+ regulation of muscle contraction. Biochemistry 13:2697–2703
Rao JN, Rivera-Santiago R, Li XE, Lehman W, Dominguez R (2012) Structural analysis of smooth muscle tropomyosin α and β isoforms. J Biol Chem 287:3165–3174
Schmidt WM, Lehman W, Moore JR (2015) Direct observation of tropomyosin binding to actin filaments. Cytoskeleton 72:292–303. doi:10.1002/cm.21225
Vibert P, Craig R, Lehman W (1997) Steric-model for activation of muscle thin filaments. J Mol Biol 266:8–14
von der Ecken J, Müller M, Lehman W, Manstein DJ, Penczek PA, Raunser S (2014) Structure of the F-actin-tropomyosin complex. Nature 519:114–117
Wegner A (1980) The interaction of alpha, alpha-and alpha, beta-tropomyosin with actin filaments. FEBS Lett 119:245–248
Whitby FG, Phillips GN Jr (2000) Crystal structure of tropomyosin at 7 Angstroms resolution. Proteins 38:49–59
Yang S, Barbu-Tudoran L, Orzechowski M, Craig R, Trinick J, White H, Lehman W (2014) Three-dimensional organization of troponin on cardiac thin filaments in the relaxed state. Biophys J 106:855–864
Acknowledgments
These studies were supported by NIH grant R37HL036153 to W.L. The Massachusetts Green High Performance Computing Center and the IWR (University of Heidelberg) provided computational resources.
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Rynkiewicz, M.J., Schott, V., Orzechowski, M. et al. Electrostatic interaction map reveals a new binding position for tropomyosin on F-actin. J Muscle Res Cell Motil 36, 525–533 (2015). https://doi.org/10.1007/s10974-015-9419-z
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DOI: https://doi.org/10.1007/s10974-015-9419-z