Muscle Crossbridge Positions from Equatorial Diffraction Data: An Approach Towards Solving the Phase Problem

  • John Squire
  • Jeffrey Harford
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 37)

Abstract

Following a discussion of the problems involved in the analysis of X-ray diffraction data from muscle, a description is given of a possible procedure for solving the phase problem in the case of equatorial diffraction data. The approach involves the use of the Patterson Function which can be determined unambiguously from the observed diffracted intensities. The method is tested using five different muscle-like model density distributions for which the correct phases can be calculated directly. It is then applied to the equatorial X-ray diffraction data from relaxed frog sartorius muscle where it selects a phase set which is also the most likely to be correct on the basis of other available data on frog muscle. This phase set gives rise to a Fourier synthesis map in which the crossbridges form a uniform shelf of density around the myosin filament backbones. Possible lateral movements of the crossbridges from this relaxed configuration in active and rigor muscle are discussed. The approach to solving the phase problem is now being applied to data from fish muscle, insect flight muscle and crab muscle. It should also have its application to other fibrous materials apart from muscle.

Keywords

Hexagonal Pepe Croup 

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References

  1. Freundlich, A., Luther, P.K. and Squire, J.M. (1980). High-voltage electron microscopy of crossbridge interactions in striated muscle. J. Muscle Res. 1: 321–343.CrossRefGoogle Scholar
  2. Haselgrove, T.C., and Huxley, H.E. (1973). X-ray evidence for radial crossbridge movement and for the sliding filament model in actively contracting skeletal muscle. J. Mol. Biol. 77: 549–568.PubMedCrossRefGoogle Scholar
  3. Haselgrove, J.C., Stewart, M. and Huxley, H.E. (1976). Cross-bridge movement during muscular contraction. Nature 261: 606–808.PubMedCrossRefGoogle Scholar
  4. Huxley, H.E. and Brown, W. (1967) The low-angle X-ray diagram of vertebrate striated muscle and its behavior during contraction and rigor. J. Mol. Biol. 30: 383–434.PubMedCrossRefGoogle Scholar
  5. Huxley, H.E., Faruqi, A.R., Bordas, J., Koch, M.H.J. and Milch, J.R. (1980). The use of synchrotron radiation in time-resolved X-ray diffraction studies of myosin layer-line reflections during muscle contraction Nature 284: 140–143.Google Scholar
  6. Huxley, H.E., Simmons, R.M., Faruqi, A.R,. Kress, M., Bordas, J. and Koch, M.H.J. (1981) Millisecond time-resolved changes in X-ray reflections from contracting muscle during rapid mechanical transients, recorded using synchrotron radiation. Proc. Nat. Acad. Sci. 78: 2297–2301.PubMedCrossRefGoogle Scholar
  7. Luther, P.K. and Squire, J.M. (1978). Three-dimensional structure of the vertebrate muscle M-region. J. Mol, Biol. 125: 313–324.CrossRefGoogle Scholar
  8. Luther, P.K. and Squire, J.M. (1980). Three-dimensional structure of the vertebrate muscle A-band. II. The myosin filament superlattice. J. Mol. Biol. 141: 409–439.PubMedCrossRefGoogle Scholar
  9. Luther, P.K., Crowther, A.R. and Squire, J.M. (1982). Three-dimensional structure of the M-band in fish muscle. Blophys. J. 37: 51a.Google Scholar
  10. Luther, P.K., Munro, P.M.G. and Squire, J.M. (1981). Three-dimensional structure of the vertebrate muscle A-band. J. Mol. Biol. 151: 703–730.PubMedCrossRefGoogle Scholar
  11. Lymn, R.W. and Cohen, G.H. (1975). Equatorial X-ray reflections and cross arm movement in skeletal muscle. Nature 258: 770–772.PubMedCrossRefGoogle Scholar
  12. Maw, M.C. and Rowe, A.J. (1980). Fraying of A-filaments into three subfilaments. Nature 286: 412–414.PubMedCrossRefGoogle Scholar
  13. Offer, G., Couch, J., O’Brien, E.J. and Elliott, A. (1981). Arrangement of cross-bridges in insect flight muscle in rigor. J. Mol. Biol. 151: 663–702.PubMedCrossRefGoogle Scholar
  14. Stewart, M., Ashton, F.T., Lieberson, R. and Pepe, F.A. (1981). The myosin filament. IX. Determinations of subfilament positions by computer processing of electron micrographs. J. Mol. Biol. 153: 381–392.PubMedCrossRefGoogle Scholar
  15. Squire, J.M. (1972). General model of myosin filament structure. II. Myosin filaments and cross-bridge interactions in vertebrate striated and insect flight muscles. J. Mol. Biol. 72: 125–138.PubMedCrossRefGoogle Scholar
  16. Squire, J.M. (1981). The structural basis of muscular contraction. Plenum Publishing Corp., New York.CrossRefGoogle Scholar
  17. Yu, L.C., Hartt, J.E. and Podolsky, R.J., (1979). Equatorial X-ray intensities and isometric force levels in frog sartorius muscle. J. Mol. Biol. 132: 53–68.PubMedCrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • John Squire
    • 1
  • Jeffrey Harford
    • 1
  1. 1.Biopolymer GroupImperial CollegeLondon SW7England

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