scholarly journals The vertebrate skeletal muscle thick filaments are not three-stranded. Reinterpretation of some experimental data.

2002 ◽  
Vol 49 (4) ◽  
pp. 841-853 ◽  
Author(s):  
Ludmila Skubiszak ◽  
Leszek Kowalczyk
Keyword(s):  
Skeletal Muscle ◽  
Mass Distribution ◽  
Thick Filament ◽  
X Ray Diffraction ◽  
Bipolar Structure ◽  
X Ray ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Cross Bridges ◽  
Vertebrate Skeletal Muscle

Computer simulation of mass distribution within the model and Fourier transforms of images depicting mass distribution are explored for verification of two alternative modes of the myosin molecule arrangement within the vertebrate skeletal muscle thick filaments. The model well depicting the complete bipolar structure of the thick filament and revealing a true threefold-rotational symmetry is a tube covered by two helices with a pitch of 2 x 43 nm due to arrangement of the myosin tails along a helical path and grouping of all myosin heads in the crowns rotated by 240 degrees and each containing three cross-bridges separated by 0 degrees, 120 degrees, and 180 degrees. The cross-bridge crown parameters are verified by EM images as well as by optical and low-angle X-ray diffraction patterns found in the literature. The myosin tail arrangement, at which the C-terminus of about 43-nm length is near-parallel to the filament axis and the rest of the tail is quite strongly twisted around, is verified by the high-angle X-ray diffraction patterns. A consequence of the new packing is a new way of movement of the myosin cross-bridges, namely, not by bending in the hinge domains, but by unwrapping from the thick filament surface towards the thin filaments along a helical path.

An ultrastructural study of crossbridge arrangement in the fish skeletal muscle thick filament

1989 ◽  
Vol 94 (3) ◽  
pp. 391-401
Author(s):  
R.W. Kensler ◽  
M. Stewart
Keyword(s):  
Skeletal Muscle ◽  
Fourier Transforms ◽  
Thick Filament ◽  
Fish Muscle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thick Filaments ◽  
Gold Fish ◽  
Diffraction Patterns ◽  
Cross Bridges

A procedure has been developed for isolating gold-fish skeletal muscle thick filaments that preserves the near-helical arrangement of the myosin cross-bridges under relaxing conditions. These filaments have been examined by electron microscopy and computer image analysis. Electron micrographs of the negatively stained filaments showed a clear periodicity associated with the crossbridges, with an axial repeat every 42.9 nm. Computed Fourier transforms of the negatively stained filaments showed a series of layer lines confirming this periodicity, and were similar to the X-ray diffraction patterns of fish muscle obtained by J. Hartford and J. Squire. Analysis of the computed transform data and filtered images of the isolated fish filaments demonstrated that the myosin crossbridges lie along three strands. Platinum shadowing demonstrated that the strands have a right-handed orientation, and computed transforms and filtered images of the shadowed filaments suggest that the crossbridges are perturbed both axially and azimuthally from an ideal helical arrangement.

scholarly journals Frog skeletal muscle thick filaments are three-stranded.

1983 ◽  
Vol 96 (6) ◽  
pp. 1797-1802 ◽  
Author(s):  
R W Kensler ◽  
M Stewart
Keyword(s):  
Skeletal Muscle ◽  
Optical Diffraction ◽  
Layer Line ◽  
X Ray Diffraction ◽  
Computer Image Analysis ◽  
X Ray ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Meridional Reflection ◽  
Vertebrate Skeletal Muscle

A procedure has been developed for isolating and negatively staining vertebrate skeletal muscle thick filaments that preserves the arrangement of the myosin crossbridges. Electron micrographs of these filaments showed a clear periodicity associated with crossbridges with an axial repeat of 42.9 nm. Optical diffraction patterns of these images showed clear layer lines and were qualitatively similar to published x-ray diffraction patterns, except that the 1/14.3-nm meridional reflection was somewhat weaker. Computer image analysis of negatively stained images of these filaments has enabled the number of strands to be established unequivocally. Both reconstructed images from layer line data and analysis of the phases of the inner maxima of the first layer line are consistent only with a three-stranded structure and cannot be reconciled with either two- or four-stranded models.

scholarly journals An electron microscopic and optical diffraction analysis of the structure of Limulus telson muscle thick filaments.

1982 ◽  
Vol 92 (2) ◽  
pp. 443-451 ◽  
Author(s):  
R W Kensler ◽  
R J Levine
Keyword(s):  
Electron Microscopy ◽  
Diffraction Analysis ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Cross Bridges

Long, thick filaments (greater than 4.0 micrometer) rapidly and gently isolated from fresh, unstimulated Limulus muscle by an improved procedure have been examined by electron microscopy and optical diffraction. Images of negatively stained filaments appear highly periodic with a well-preserved myosin cross-bridge array. Optical diffraction patterns of the electron micrographs show a wealth of detail and are consistent with a myosin helical repeat of 43.8 nm, similar to that observed by x-ray diffraction. Analysis of the optical diffraction patterns, in conjunction with the appearance in electron micrographs of the filaments, supports a model for the filament in which the myosin cross-bridges are arranged on a four-stranded helix, with 12 cross-bridges per turn or each helix, thus giving an axial repeat every third level of cross-bridges (43.8 nm).

scholarly journals Myosin molecule packing within the vertebrate skeletal muscle thick filaments. A complete bipolar model.

2002 ◽  
Vol 49 (4) ◽  
pp. 829-840 ◽  
Author(s):  
Ludmila Skubiszak ◽  
Leszek Kowalczyk
Keyword(s):  
Skeletal Muscle ◽  
Computer Modelling ◽  
Thick Filament ◽  
Myosin Molecule ◽  
Bipolar Structure ◽  
Cross Bridge ◽  
Filament Axis ◽  
Thick Filaments ◽  
C Terminus ◽  
Vertebrate Skeletal Muscle

Computer modelling related to the real dimensions of both the whole filament and the myosin molecule subfragments has revealed two alternative modes for myosin molecule packing which lead to the head disposition similar to that observed by EM on the surface of the cross-bridge zone of the relaxed vertebrate skeletal muscle thick filaments. One of the modes has been known for three decades and is usually incorporated into the so-called three-stranded model. The new mode differs from the former one in two aspects: (1) myosin heads are grouped into asymmetrical cross-bridge crowns instead of symmetrical ones; (2) not the whole myosin tail, but only a 43-nm C-terminus of each of them is straightened and near-parallel to the filament axis, the rest of the tail is twisted. Concurrent exploration of these alternative modes has revealed their influence on the filament features. The parameter values for the filament models as well as for the building units depicting the myosin molecule subfragments are verified by experimental data found in the literature. On the basis of the new mode for myosin molecule packing a complete bipolar structure of the thick filament is created.

scholarly journals Backward Movements of Cross-Bridges by Application of Stretch and by Binding of MgADP to Skeletal Muscle Fibers in the Rigor State as Studied by X-Ray Diffraction

1999 ◽  
Vol 76 (4) ◽  
pp. 1770-1783 ◽  
Author(s):  
Yasunori Takezawa ◽  
Duck-Sool Kim ◽  
Masaki Ogino ◽  
Yasunobu Sugimoto ◽  
Takakazu Kobayashi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rigor State ◽  
Skeletal Muscle Fibers ◽  
Cross Bridges

scholarly journals Multiscale Model Predictions of X-Ray Diffraction Patterns in Contracting Skeletal Muscle

2011 ◽  
Vol 100 (3) ◽  
pp. 585a
Author(s):  
Srboljub M. Mijailovich ◽  
Boban Stojanovic ◽  
Thomas Irving
Keyword(s):  
Skeletal Muscle ◽  
Multiscale Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Model Predictions ◽  
Diffraction Patterns

scholarly journals Dependence of thick filament structure in relaxed mammalian skeletal muscle on temperature and interfilament spacing

2021 ◽  
Vol 153 (3) ◽  
Author(s):  
Marco Caremani ◽  
Luca Fusi ◽  
Marco Linari ◽  
Massimo Reconditi ◽  
Gabriella Piazzesi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Thick Filament ◽  
Structural Basis ◽  
Mammalian Skeletal Muscle ◽  
X Ray ◽  
Physiological Temperature ◽  
Thick Filaments ◽  
Filament Structure ◽  
Intact Muscle ◽  
Resting Muscle

Contraction of skeletal muscle is regulated by structural changes in both actin-containing thin filaments and myosin-containing thick filaments, but myosin-based regulation is unlikely to be preserved after thick filament isolation, and its structural basis remains poorly characterized. Here, we describe the periodic features of the thick filament structure in situ by high-resolution small-angle x-ray diffraction and interference. We used both relaxed demembranated fibers and resting intact muscle preparations to assess whether thick filament regulation is preserved in demembranated fibers, which have been widely used for previous studies. We show that the thick filaments in both preparations exhibit two closely spaced axial periodicities, 43.1 nm and 45.5 nm, at near-physiological temperature. The shorter periodicity matches that of the myosin helix, and x-ray interference between the two arrays of myosin in the bipolar filament shows that all zones of the filament follow this periodicity. The 45.5-nm repeat has no helical component and originates from myosin layers closer to the filament midpoint associated with the titin super-repeat in that region. Cooling relaxed or resting muscle, which partially mimics the effects of calcium activation on thick filament structure, disrupts the helical order of the myosin motors, and they move out from the filament backbone. Compression of the filament lattice of demembranated fibers by 5% Dextran, which restores interfilament spacing to that in intact muscle, stabilizes the higher-temperature structure. The axial periodicity of the filament backbone increases on cooling, but in lattice-compressed fibers the periodicity of the myosin heads does not follow the extension of the backbone. Thick filament structure in lattice-compressed demembranated fibers at near-physiological temperature is similar to that in intact resting muscle, suggesting that the native structure of the thick filament is largely preserved after demembranation in these conditions, although not in the conditions used for most previous studies with this preparation.

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