scholarly journals Resting myosin cross-bridge configuration in frog muscle thick filaments.

1986 ◽  
Vol 102 (2) ◽  
pp. 610-618 ◽  
Author(s):  
M Cantino ◽  
J Squire
Keyword(s):  
Myosin Head ◽  
Freeze Fracture ◽  
Optical Diffraction ◽  
Outer Diameter ◽  
X Ray ◽  
Cross Bridge ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Cross Bridges ◽  
The Right

Clear images of myosin filaments have been seen in shadowed freeze-fracture replicas of single fibers of relaxed frog semitendinosus muscles rapidly frozen using a dual propane jet freezing device. These images have been analyzed by optical diffraction and computer averaging and have been modelled to reveal details of the myosin head configuration on the right-handed, three-stranded helix of cross-bridges. Both the characteristic 430-A and 140-150-A repeats of the myosin cross-bridge array could be seen. The measured filament backbone diameter was 140-160 A, and the outer diameter of the cross-bridge array was 300 A. Evidence is presented that suggests that the observed images are consistent with a model in which both of the heads of one myosin molecule tilt in the same direction at an angle of approximately 50-70 degrees to the normal to the filament long axis and are slewed so that they lie alongside each other and their radially projected density lies along the three right-handed helical tracks. Any perturbation of the myosin heads away from their ideal lattice sites needed to account for x-ray reflections not predicted for a perfect helix must be essentially along the three helical tracks of cross-bridges. Little trace of the presence of non-myosin proteins could be seen.

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 Recent X-ray Diffraction and Electron Microscope Studies of Striated Muscle

1967 ◽  
Vol 50 (6) ◽  
pp. 71-83 ◽  
Author(s):  
H. E. Huxley
Keyword(s):  
Active Sites ◽  
Striated Muscle ◽  
Structural Features ◽  
Actin Binding ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
The Cross ◽  
Cross Bridges

The sliding filament model for muscular contraction supposes that an appropriately directed force is developed between the actin and myosin filaments by some process in which the cross-bridges are involved. The cross-bridges between the filaments are believed to represent the parts of the myosin molecules which possess the active sites for ATPase activity and actin-binding ability, and project out sidewise from the backbone of the thick filaments. The arrangement of the cross-bridges is now being studied by improved low-angle X-ray diffraction techniques, which show that in a resting muscle, they are arranged approximately but not exactly in a helical pattern, and that there are other structural features of the thick filaments which give rise to additional long periodicities shown up by the X-ray diagram. The actin filaments also contain helically arranged subunits, and both the subunit repeat and the helical repeat are different from those in the myosin filaments. Diffraction diagrams can be obtained from muscles in rigor (when permanent attachment of the cross-bridges to the actin subunits takes place) and now, taking advantage of the great increase in the speed of recording, from actively contracting muscles. These show that changes in the arrangement of the cross-bridges are produced under both these conditions and are no doubt associated in contraction with the development of force. Thus configurational changes of the myosin component in muscle have been demonstrated: these take place without any significant over-all change in the length of the filaments.

scholarly journals Electron microscopic and optical diffraction analysis of the structure of scorpion muscle thick filaments.

1985 ◽  
Vol 101 (2) ◽  
pp. 395-401 ◽  
Author(s):  
R W Kensler ◽  
R J Levine ◽  
M Stewart
Keyword(s):  
Diffraction Analysis ◽  
Fourier Transforms ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Electron Microscopic ◽  
Cross Bridge ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Cross Bridges ◽  
Tail Muscle

We rapidly and gently isolated thick filaments from scorpion tail muscle by a modification of the technique previously described for isolating Limulus thick filaments. Images of negatively stained filaments appeared to be highly periodic, with a well-preserved myosin cross-bridge array. Optical diffraction patterns of the electron micrograph images were detailed and similar to optical diffraction patterns from Limulus and tarantula thick filaments. Analysis of the optical diffraction patterns and computed Fourier transforms, together with the appearance of the filaments in the micrographs, suggested a model for the filaments in which the myosin cross-bridges were arranged on four helical strands with 12 cross-bridges per turn of each strand, thus giving the observed repeat every third cross-bridge level. Comparison of the scorpion thick filaments with those isolated from the closely related chelicerate arthropods, Limulus and tarantula, revealed that they were remarkably similar in appearance and helical symmetry but different in diameter.

Structural cross-bridges between microtubules and mitochondria in central axons of an insect (Periplaneta americana)

1977 ◽  
Vol 27 (1) ◽  
pp. 255-272
Author(s):  
D.S. Smith ◽  
U. Jarlfors ◽  
M.L. Cayer
Keyword(s):  
Electron Micrographs ◽  
Mitochondrial Membrane ◽  
Periplaneta Americana ◽  
Freeze Fracture ◽  
Outer Mitochondrial Membrane ◽  
Thin Sections ◽  
Cross Bridge ◽  
Multiple Association ◽  
Random Models ◽  
Cross Bridges

The distribution of microtubules and mitochondria in central axons of an insect (Periplaneta americana) is assessed by comparison between counts on micrographs and computed axon random ‘models’. These studies show that the observed multiple association of microtubules with individual mitochondria is statistically highly significant. Electron micrographs of thin sections show that linkage is effected by physical cross-bridge, possibly comprising components from the microtubule and mitochondrion. Linear particle arrays are described on the outer mitochondrial membrane in freeze-fracture replicas, and tentatively related to the bridges seen in thin sections. The results are discussed in terms of proposed roles of microtubules in neurons and other cells.

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 The Cross-Bridge Spring: Can Cool Muscles Store Elastic Energy?

Science ◽  
2013 ◽  
Vol 340 (6137) ◽  
pp. 1217-1220 ◽  
Author(s):  
N. T. George ◽  
T. C. Irving ◽  
C. D. Williams ◽  
T. L. Daniel
Keyword(s):  
Energy Storage ◽  
Elastic Energy ◽  
Molecular Motors ◽  
High Speed ◽  
Mechanical Energy ◽  
Elastic Strain Energy ◽  
Time Resolved ◽  
X Ray ◽  
Cross Bridge ◽  
Cross Bridges

Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy. By using time-resolved small-angle x-ray diffraction paired with in situ measurements of mechanical energy exchange in flight muscles of Manduca sexta, we produced high-speed movies of x-ray equatorial reflections, indicating cross-bridge association with myofilaments. A temperature gradient within the flight muscle leads to lower cross-bridge cycling in the cooler regions. Those cross-bridges could elastically return energy at the extrema of muscle lengthening and shortening, helping drive cyclic wing motions. These results suggest that cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.

scholarly journals Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres

2021 ◽  
Vol 22 (16) ◽  
pp. 8526
Author(s):  
Venus Joumaa ◽  
Ian C. Smith ◽  
Atsuki Fukutani ◽  
Timothy R. Leonard ◽  
Weikang Ma ◽  
...  
Keyword(s):  
Steady State ◽  
Small Angle ◽  
Isometric Contraction ◽  
Sarcomere Length ◽  
Force Enhancement ◽  
X Ray ◽  
Cross Bridge ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Cross Bridges

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.

scholarly journals Different Myosin Head Conformations in Bony Fish Muscles Put into Rigor at Different Sarcomere Lengths

2018 ◽  
Vol 19 (7) ◽  
pp. 2091 ◽  
Author(s):  
Felicity Eakins ◽  
Jeffrey J. Harford ◽  
Carlo Knupp ◽  
Manfred Roessle ◽  
John M. Squire
Keyword(s):  
Sarcomere Length ◽  
Myosin Head ◽  
Bony Fish ◽  
Actin Binding ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fish Muscles ◽  
Cross Bridge ◽  
Butanedione Monoxime ◽  
Tension Generation

At a resting sarcomere length of approximately 2.2 µm bony fish muscles put into rigor in the presence of BDM (2,3-butanedione monoxime) to reduce rigor tension generation show the normal arrangement of myosin head interactions with actin filaments as monitored by low-angle X-ray diffraction. However, if the muscles are put into rigor using the same protocol but stretched to 2.5 µm sarcomere length, a markedly different structure is observed. The X-ray diffraction pattern is not just a weaker version of the pattern at full overlap, as might be expected, but it is quite different. It is compatible with the actin-attached myosin heads being in a different conformation on actin, with the average centre of cross-bridge mass at a higher radius than in normal rigor and the myosin lever arms conforming less to the actin filament geometry, probably pointing back to their origins on their parent myosin filaments. The possible nature of this new rigor cross-bridge conformation is discussed in terms of other well-known states such as the weak binding state and the ‘roll and lock’ mechanism; we speculate that we may have trapped most myosin heads in an early attached strong actin-binding state in the cross-bridge cycle on actin.

scholarly journals Structure and paramyosin content of tarantula thick filaments.

1983 ◽  
Vol 97 (1) ◽  
pp. 186-195 ◽  
Author(s):  
R J Levine ◽  
R W Kensler ◽  
M C Reedy ◽  
W Hofmann ◽  
H A King
Keyword(s):  
Evolutionary Relationship ◽  
Radial Distance ◽  
Thick Filament ◽  
Optical Diffraction ◽  
Thin Filaments ◽  
Biochemical Characteristics ◽  
Thick Filaments ◽  
Cross Bridges ◽  
Centers Of Mass ◽  
Relationship Of

Muscle fibers of the tarantula femur exhibit structural and biochemical characteristics similar to those of other long-sarcomere invertebrate muscles, having long A-bands and long thick filaments. 9-12 thin filaments surround each thick filament. Tarantula muscle has a paramyosin:myosin heavy chain molecular ratio of 0.31 +/- 0.079 SD. We studied the myosin cross-bridge arrangement on the surface of tarantula thick filaments on isolated, negatively stained, and unidirectionally metal-shadowed specimens by electron microscopy and optical diffraction and filtering and found it to be similar to that previously described for the thick filaments of muscle of the closely related chelicerate arthropod, Limulus. Cross-bridges are disposed in a four-stranded right-handed helical arrangement, with 14.5-nm axial spacing between successive levels of four bridges, and a helical repeat period every 43.5 nm. The orientation of cross-bridges on the surface of tarantula filaments is also likely to be very similar to that on Limulus filaments as suggested by the similarity between filtered images of the two types of filaments and the radial distance of the centers of mass of the cross-bridges from the surfaces of both types of filaments. Tarantula filaments, however, have smaller diameters than Limulus filaments, contain less paramyosin, and display structure that probably reflects the organization of the filament backbone which is not as apparent in images of Limulus filaments. We suggest that the similarities between Limulus and tarantula thick filaments may be governed, in part, by the close evolutionary relationship of the two species.

scholarly journals LOCUS AND STATE OF AGGREGATION OF MYOSIN IN TISSUE SECTIONS OF VERTEBRATE SMOOTH MUSCLE

1970 ◽  
Vol 44 (1) ◽  
pp. 52-61 ◽  
Author(s):  
Bernard J. Panner ◽  
Carl R. Honig
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Low Ph ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tissue Sections ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
And Storage

Structures with the characteristics of molecular myosin were identified by electron microscopy in tissue sections of vertebrate smooth muscle. No thick filaments of myosin were found regardless of preparative procedures, which included fixation at rest and in contraction, glycerine extraction, and storage at low pH prior to fixation. Absence of thick myosin filaments and presence of what appear to be myosin molecules is in accord with conclusions based on X-ray diffraction (3, 12) and birefringence data (4) from living smooth muscles at rest and in contraction. Explanations are provided for appearances thought by others (6, 20, 21) to represent thick myosin filaments. Our present observations are in accord with the model for smooth muscle contraction which we have previously proposed (1).

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