Assembly of myosin

doi:10.1016/0022-2836(71)90317-2

Journal of Molecular Biology

Volume 59, Issue 3, 14 August 1971, Pages 531-532, IN11-IN13, 533-535

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Abstract

Myosin and its helical subfragments form bipolar “segment” aggregates which may be related to the bare zone of the thick filament. Two distinct modes of aggregation have now been observed: one with an overlap of 1300 Å and another with an overlap of about 900 Å. Both are consistent with a value of 1450 Å for the length of the rod. The helical arrangement of the bridges on the thick filament has been determined by X-ray diffraction results. Placing rods of length 1450 Å on this surface lattice generates the molecular overlaps found in the in vitro “segment” aggregates.

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Cited by (55)

Skip residues and charge interactions in myosin II coiled-coils: Implications for molecular packing
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Molecular packing of myosin II coiled-coil rods into myosin filaments and the role of skip residues in the heptad sequence have been investigated. Sequence comparison of rods from skeletal, smooth and non-muscle myosin II shows that different myosin II subtypes have significantly different charge distributions. Analysis of the ionic interactions between adjacent rods with changing molecular overlap relates the different patterns of charge to the different structures of skeletal and smooth muscle myosin II filaments. It is shown in the case of skeletal muscle myosin II that the skip residues have a critical role in keeping these unique patterns of charge in perfect phase. Only one of the previously suggested packing models for myosin II filaments, with a slight modification, is supported, since it satisfies all the sequence-predicted axial shifts between adjacent rods. Such analysis significantly advances understanding of myosin filament assembly properties and will help to provide a basis for the proper understanding of myosin-associated diseases.
Filament assembly properties of the sarcomeric myosin heavy chain
1999, Poultry Science
Meat is the edible muscle tissue of animals. The sarcomere is the fundamental functional unit of muscle. Growth and development of muscle is accomplished by the highly ordered accretion and assembly of the constituent proteins in the sarcomere. Primary amino acid sequence elements of the constitutive proteins carry the information necessary for determining the final architecture of the sarcomere. The mechanisms by which the constitutive proteins are assembled and function together to form the sarcomere and produce muscle contraction is just now beginning to be understood. The predominant protein in the sarcomere, found in the thick filament system, is myosin. In physiological buffers purified myosin spontaneously assembles into a synthetic thick filament with a dramatic resemblance to the native thick filament. Some of the amino acid sequence elements contributing to myosin's assembly properties may also be critical to myosin's solubility function, which is so crucial to the manufacture of high quality prepared meat products. This review summarizes recent experimental results contributing to our understanding of the mechanism of sarcomeric muscle myosin assembly.
Functional properties of myosin isoforms in avian muscle
1999, Poultry Science
Sarcomeric myosin is the major skeletal muscle protein and is encoded by a large and complex multigene family whose members are differentially expressed in developing and adult muscle cells. The structure and function of sarcomeric myosins have been extensively analyzed and many myosin genes have now been cloned and sequenced. This manuscript reviews the broad spectrum of myosin research with emphasis on studies in avian systems and discusses how advances in myosin isoform analysis have contributed to muscle and meat science.
MgATP specifically controls in vitro self-assembly of vertebrate skeletal myosin in the physiological pH range
1985, Journal of Molecular Biology
The appearances in the electron microscope of rat and rabbit skeletal muscle myosin filaments and rod aggregates, formed in the presence of variable amounts of MgATP, were compared at different pH values. It is shown that small amounts of MgATP, similar to those sufficient to trigger the dissociation of the actomyosin complex, were able to modify the geometry of myosin filaments profoundly in the physiological pH range, whereas the conformation of rod aggregates remained unchanged even in the presence of high concentrations of MgATP. Myosin filaments formed in the absence of MgATP displayed the classical spindle-shaped conformation and variable diameters at all pH values, whereas myosin filaments formed in the presence of MgATP in the physiological pH range had constant diameters, similar to those of natural thick filaments. These filaments of constant diameter frayed, rapidly and reversibly, into two types of subfilaments with respective diameters of 4 to 5 nm and 9 to 10 nm, when the pH of the medium was raised above 7.2. Spindle-shaped myosin filaments and rod aggregates remained unchanged by such small changes in pH. It was possible to change the conformation of preformed spindle-shaped filaments by simply adding MgATP to the medium, but this reaction was slow and took several hours to be completed. Relatively high concentrations of MgATP, similar to those in the living cell, increased the solubility of both myosin filaments and rod aggregates in the alkaline pH range (pH ≥ 7.0). Low pH values (≤ 6.5) and excess free Mg²⁺ (≥ 6 to 7 mm) abolished both the specific effect of MgATP on myosin filament conformation and its solubilizing effect on both myosin filaments and rod aggregates. The degree of purity of the myosin preparations and the level of phosphorylation of the LC-2 light chains did not influence filament behaviour noticeably and rat and rabbit myosins behaved similarly.
Structure of the myosin crossbridge lattice in insect flight muscle
1983, Journal of Molecular Biology
Freeze fracture and deep-etching of quick-frozen insect flight muscles provides unusually clear views of thick filament projections in rigor and relaxed states. In rigor, these projections form crossbridges that are deployed helically. The tracks of these helices are left-handed, repeat every ∼38 nm, tilt at ∼42° to the muscle axis, and, when viewed on edge, produce the unique “double chevron” pattern of crossbridges that characterizes this muscle type in thin sections (Reedy, 1968). These helical parameters substantiate Reedy's earlier deduction that rigor crossbridges form two-start helices in this muscle. On the other hand, deep-etchings of insect flight muscles relaxed with Mg-ATP before freezing do not fit with earlier results. Contrary to earlier thin section views and the expectations of X-ray diffraction, thick filaments in such relaxed muscles display no hint of a 14·5 nm axial periodicity; instead, their projections appear to be very disordered. This suggests that when crossbridges are detached, they are free to “wobble” by at least ±7 nm in the axial direction and thus obscure their points of origin from the thick filaments. With the images of detached crossbridges in mind, closer inspection of rigor thick filaments yields no indication of any “extra” projections between the helically deployed ones, i.e. there is no indication of any detached crossbridges in rigor muscles. Thus in this type of muscle, at least, the establishment of a rigor pattern may not involve a “selection” of suitably located myosin heads from a larger population, as is generally thought, but may instead involve a systematic redistribution of the whole population of heads until all of them became crossbridges.
An in vitro study of the interactions of skeletal muscle M-protein and creatine kinase with myosin and its subfragments
1983, Journal of Molecular Biology
Two proteins reported to be located in the M-band of skeletal muscle are M-protein (M_r 160,000) and creatine kinase (M_r 83,000). We have isolated and purified these proteins from adult chicken pectoralis muscle, and have studied their in vitro interactions with myosin, heavy meromyosin, light meromyosin and subfragment-2 in order to obtain a fuller understanding of the role these proteins play in the M-band of skeletal muscle. Experiments using the techniques of analytical ultracentrifugation, affinity chromatography and electron microscopy were carried out near physiological pH and ionic strength, under which conditions the M-band proteins are known to be firmly bound to the myofibril in situ. The results of our studies indicate that such interactions are either weak or absent in vitro. Discrepancies between our results and those from several other studies are discussed. We conclude that additional components may be required in order to observe interactions in vitro which are similar to those present in the intact myofibril.

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^☆: This work was supported by Public Health Service grants AM-02633 to one of us (C. C.) and AM-04762 to another of the authors (S.L.); a Public Health Service Research Career Program Award K3-AM-10630, a grant from the Muscular Dystrophy Association of America, Inc., and a National Science Foundation grant GB-8616 were awarded to the latter author (S.L.).

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Journal of Molecular Biology

Letter to the editorAssembly of myosin☆

Abstract

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Letter to the editor
Assembly of myosin☆