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. 1991 Nov 1;115(3):689–703. doi: 10.1083/jcb.115.3.689

The structural basis for the intrinsic disorder of the actin filament: the "lateral slipping" model

PMCID: PMC2289171  PMID: 1918159

Abstract

Three-dimensional (3-D) helical reconstructions computed from electron micrographs of negatively stained dispersed F-actin filaments invariably revealed two uninterrupted columns of mass forming the "backbone" of the double-helical filament. The contact between neighboring subunits along the thus defined two long-pitch helical strands was spatially conserved and of high mass density, while the intersubunit contact between them was of lower mass density and varied among reconstructions. In contrast, phalloidinstabilized F-actin filaments displayed higher and spatially more conserved mass density between the two long-pitch helical strands, suggesting that this bicyclic hepta-peptide toxin strengthens the intersubunit contact between the two strands. Consistent with this distinct intersubunit bonding pattern, the two long-pitch helical strands of unstabilized filaments were sometimes observed separated from each other over a distance of two to six subunits, suggesting that the intrastrand intersubunit contact is also physically stronger than the interstrand contact. The resolution of the filament reconstructions, extending to 2.5 nm axially and radially, enabled us to reproducibly "cut out" the F- actin subunit which measured 5.5 nm axially by 6.0 nm tangentially by 3.2 nm radially. The subunit is distinctly polar with a massive "base" pointing towards the "barbed" end of the filament, and a slender "tip" defining its "pointed" end (i.e., relative to the "arrowhead" pattern revealed after stoichiometric decoration of the filaments with myosin subfragment 1). Concavities running approximately parallel to the filament axis both on the inner and outer face of the subunit define a distinct cleft separating the subunit into two domains of similar size: an inner domain confined to radii less than or equal to 2.5-nm forms the uninterrupted backbone of the two long-pitch helical strands, and an outer domain placed at radii of 2-5-nm protrudes radially and thus predominantly contributes to the outer part of the massive base. Quantitative evaluation of successive crossover spacings along individual F-actin filaments revealed the deviations from the mean repeat to be compensatory, i.e., short crossovers frequently followed long ones and vice versa. The variable crossover spacings and diameter of the F-actin filament together with the local unraveling of the two long-pitch helical strands are explained in terms of varying amounts of compensatory "lateral slipping" of the two strands past each other roughly perpendicular to the filament axis. This intrinsic disorder of the actin filament may enable the actin moiety to play a more active role in actin-myosin-based force generation than merely act as a rigid passive cable as has hitherto been assumed.

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Selected References

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  1. Aebi U., Millonig R., Salvo H., Engel A. The three-dimensional structure of the actin filament revisited. Ann N Y Acad Sci. 1986;483:100–119. doi: 10.1111/j.1749-6632.1986.tb34502.x. [DOI] [PubMed] [Google Scholar]
  2. Aebi U., Pollard T. D. A glow discharge unit to render electron microscope grids and other surfaces hydrophilic. J Electron Microsc Tech. 1987 Sep;7(1):29–33. doi: 10.1002/jemt.1060070104. [DOI] [PubMed] [Google Scholar]
  3. Amos L. A. Structure of muscle filaments studied by electron microscopy. Annu Rev Biophys Biophys Chem. 1985;14:291–313. doi: 10.1146/annurev.bb.14.060185.001451. [DOI] [PubMed] [Google Scholar]
  4. Bennett P. M., Marston S. B. Calcium regulated thin filaments from molluscan catch muscles contain a caldesmon-like regulatory protein. J Muscle Res Cell Motil. 1990 Aug;11(4):302–312. doi: 10.1007/BF01766668. [DOI] [PubMed] [Google Scholar]
  5. Bullard B., Bell J., Craig R., Leonard K. Arthrin: a new actin-like protein in insect flight muscle. J Mol Biol. 1985 Apr 5;182(3):443–454. doi: 10.1016/0022-2836(85)90203-7. [DOI] [PubMed] [Google Scholar]
  6. Carlier M. F. Role of nucleotide hydrolysis in the dynamics of actin filaments and microtubules. Int Rev Cytol. 1989;115:139–170. doi: 10.1016/s0074-7696(08)60629-4. [DOI] [PubMed] [Google Scholar]
  7. Combeau C., Carlier M. F. Probing the mechanism of ATP hydrolysis on F-actin using vanadate and the structural analogs of phosphate BeF-3 and A1F-4. J Biol Chem. 1988 Nov 25;263(33):17429–17436. [PubMed] [Google Scholar]
  8. Cooper J. A. Effects of cytochalasin and phalloidin on actin. J Cell Biol. 1987 Oct;105(4):1473–1478. doi: 10.1083/jcb.105.4.1473. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Cooper J. A., Pollard T. D. Methods to measure actin polymerization. Methods Enzymol. 1982;85(Pt B):182–210. doi: 10.1016/0076-6879(82)85021-0. [DOI] [PubMed] [Google Scholar]
  10. DeRosier D. J., Censullo R. Structure of F-actin needles from extracts of sea urchin oocytes. J Mol Biol. 1981 Feb 15;146(1):77–99. doi: 10.1016/0022-2836(81)90367-3. [DOI] [PubMed] [Google Scholar]
  11. Egelman E. H. An algorithm for straightening images of curved filamentous structures. Ultramicroscopy. 1986;19(4):367–373. doi: 10.1016/0304-3991(86)90096-3. [DOI] [PubMed] [Google Scholar]
  12. Egelman E. H., DeRosier D. J. Angular disorder in actin: is it consistent with general principles of protein structure? J Mol Biol. 1991 Feb 5;217(3):405–408. doi: 10.1016/0022-2836(91)90743-p. [DOI] [PubMed] [Google Scholar]
  13. Egelman E. H., Francis N., DeRosier D. J. F-actin is a helix with a random variable twist. Nature. 1982 Jul 8;298(5870):131–135. doi: 10.1038/298131a0. [DOI] [PubMed] [Google Scholar]
  14. Egelman E. H., Francis N., DeRosier D. J. Helical disorder and the filament structure of F-actin are elucidated by the angle-layered aggregate. J Mol Biol. 1983 Jun 5;166(4):605–629. doi: 10.1016/s0022-2836(83)80286-1. [DOI] [PubMed] [Google Scholar]
  15. Egelman E. H. The structure of F-actin. J Muscle Res Cell Motil. 1985 Apr;6(2):129–151. doi: 10.1007/BF00713056. [DOI] [PubMed] [Google Scholar]
  16. Faulstich H., Schäfer A. J., Weckauf M. The dissociation of the phalloidin-actin complex. Hoppe Seylers Z Physiol Chem. 1977 Feb;358(2):181–184. doi: 10.1515/bchm2.1977.358.1.181. [DOI] [PubMed] [Google Scholar]
  17. Holmes K. C., Popp D., Gebhard W., Kabsch W. Atomic model of the actin filament. Nature. 1990 Sep 6;347(6288):44–49. doi: 10.1038/347044a0. [DOI] [PubMed] [Google Scholar]
  18. Janmey P. A., Hvidt S., Oster G. F., Lamb J., Stossel T. P., Hartwig J. H. Effect of ATP on actin filament stiffness. Nature. 1990 Sep 6;347(6288):95–99. doi: 10.1038/347095a0. [DOI] [PubMed] [Google Scholar]
  19. Kabsch W., Mannherz H. G., Suck D., Pai E. F., Holmes K. C. Atomic structure of the actin:DNase I complex. Nature. 1990 Sep 6;347(6288):37–44. doi: 10.1038/347037a0. [DOI] [PubMed] [Google Scholar]
  20. Kabsch W., Mannherz H. G., Suck D. Three-dimensional structure of the complex of actin and DNase I at 4.5 A resolution. EMBO J. 1985 Aug;4(8):2113–2118. doi: 10.1002/j.1460-2075.1985.tb03900.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Lepault J., Erk I., Nicolas G., Ranck J. L. Time-resolved cryo-electron microscopy of vitrified muscular components. J Microsc. 1991 Jan;161(Pt 1):47–57. doi: 10.1111/j.1365-2818.1991.tb03072.x. [DOI] [PubMed] [Google Scholar]
  22. Milligan R. A., Flicker P. F. Structural relationships of actin, myosin, and tropomyosin revealed by cryo-electron microscopy. J Cell Biol. 1987 Jul;105(1):29–39. doi: 10.1083/jcb.105.1.29. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Milligan R. A., Whittaker M., Safer D. Molecular structure of F-actin and location of surface binding sites. Nature. 1990 Nov 15;348(6298):217–221. doi: 10.1038/348217a0. [DOI] [PubMed] [Google Scholar]
  24. Millonig R., Salvo H., Aebi U. Probing actin polymerization by intermolecular cross-linking. J Cell Biol. 1988 Mar;106(3):785–796. doi: 10.1083/jcb.106.3.785. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Sakabe N., Sakabe K., Sasaki K., Kondo H., Ema T., Kamiya N., Matsushima M. Crystallographic studies of the chicken gizzard G-actin X DNase I complex at 5A resolution. J Biochem. 1983 Jan;93(1):299–302. doi: 10.1093/oxfordjournals.jbchem.a134168. [DOI] [PubMed] [Google Scholar]
  26. Schutt C. E., Lindberg U., Myslik J., Strauss N. Molecular packing in profilin: actin crystals and its implications. J Mol Biol. 1989 Oct 20;209(4):735–746. doi: 10.1016/0022-2836(89)90603-7. [DOI] [PubMed] [Google Scholar]
  27. Seymour J., O'Brien E. J. The position of tropomyosin in muscle thin filaments. Nature. 1980 Feb 14;283(5748):680–682. doi: 10.1038/283680a0. [DOI] [PubMed] [Google Scholar]
  28. Smith P. R., Fowler W. E., Pollard T. D., Aebi U. Structure of the actin molecule determined from electron micrographs of crystalline actin sheets with a tentative alignment of the molecule in the actin filament. J Mol Biol. 1983 Jul 5;167(3):641–660. doi: 10.1016/s0022-2836(83)80103-x. [DOI] [PubMed] [Google Scholar]
  29. Taylor K. A., Amos L. A. A new model for the geometry of the binding of myosin crossbridges to muscle thin filaments. J Mol Biol. 1981 Apr 5;147(2):297–324. doi: 10.1016/0022-2836(81)90442-3. [DOI] [PubMed] [Google Scholar]
  30. Taylor K. A., Reedy M. C., Córdova L., Reedy M. K. Three-dimensional reconstruction of rigor insect flight muscle from tilted thin sections. 1984 Jul 26-Aug 1Nature. 310(5975):285–291. doi: 10.1038/310285a0. [DOI] [PubMed] [Google Scholar]
  31. Trinick J., Cooper J., Seymour J., Egelman E. H. Cryo-electron microscopy and three-dimensional reconstruction of actin filaments. J Microsc. 1986 Mar;141(Pt 3):349–360. doi: 10.1111/j.1365-2818.1986.tb02728.x. [DOI] [PubMed] [Google Scholar]
  32. Vandekerckhove J. Actin-binding proteins. Curr Opin Cell Biol. 1990 Feb;2(1):41–50. doi: 10.1016/s0955-0674(05)80029-8. [DOI] [PubMed] [Google Scholar]
  33. Vandekerckhove J., Deboben A., Nassal M., Wieland T. The phalloidin binding site of F-actin. EMBO J. 1985 Nov;4(11):2815–2818. doi: 10.1002/j.1460-2075.1985.tb04008.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Vibert P., Craig R. Three-dimensional reconstruction of thin filaments decorated with a Ca2+-regulated myosin. J Mol Biol. 1982 May 15;157(2):299–319. doi: 10.1016/0022-2836(82)90236-4. [DOI] [PubMed] [Google Scholar]
  35. Wieland T., Faulstich H. Amatoxins, phallotoxins, phallolysin, and antamanide: the biologically active components of poisonous Amanita mushrooms. CRC Crit Rev Biochem. 1978 Dec;5(3):185–260. doi: 10.3109/10409237809149870. [DOI] [PubMed] [Google Scholar]
  36. Wieland T., de Vries J. X., Schäfer A., Faulstich H. Spectroscopic evidence for the interaction of phalloidin with actin. FEBS Lett. 1975 Jun 1;54(1):73–75. doi: 10.1016/0014-5793(75)81071-4. [DOI] [PubMed] [Google Scholar]
  37. Wrigley N. G. The lattice spacing of crystalline catalase as an internal standard of length in electron microscopy. J Ultrastruct Res. 1968 Sep;24(5):454–464. doi: 10.1016/s0022-5320(68)80048-6. [DOI] [PubMed] [Google Scholar]

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