Myosin Head Configuration in Relaxed Insect Flight Muscle: X-Ray Modeled Resting Cross-Bridges in a Pre-Powerstroke State Are Poised for Actin Binding

AL-Khayat, Hind A.; Hudson, Liam; Reedy, Michael K.; Irving, Thomas C.; Squire, John M.

doi:10.1016/s0006-3495(03)74545-7

Cited by 74 publications

(123 citation statements)

References 68 publications

(117 reference statements)

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“…Helical reconstruction in this case suggested a Class II structure. Modelling of IFM filaments by X-ray diffraction later appeared to support this type of model (AL-Khayat et al 2003).…”

Section: Ideas About Head Conformations In Resting Musclementioning

confidence: 93%

“…Woodhead et al 2005; heads within the same myosin molecule interacting). The Class II structure with heads from two different myosin molecules interacting around a single crown has been proposed for insect flight muscle myosin filaments (Lethocerus; AL-Khayat et al 2003). An unlikely fourth possibility is that the heads do not interact with each other at all (Class IV) Fig.…”

Section: Ideas About Head Conformations In Resting Musclementioning

confidence: 99%

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Muscle myosin filaments: cores, crowns and couplings

Squire

2009

Biophys Rev

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Myosin filaments in muscle, carrying the ATPase myosin heads that interact with actin filaments to produce force and movement, come in multiple varieties depending on species and functional need, but most are based on a common structural theme. The now successful journeys to solve the ultrastructures of many of these myosin filaments, at least at modest resolution, have not been without their false starts and erroneous sidetracks, but the picture now emerging is of both diversity in the rotational symmetries of different filaments and a degree of commonality in the way the myosin heads are organised in resting muscle. Some of the remaining differences may be associated with how the muscle is regulated. Several proteins in cardiac muscle myosin filaments can carry mutations associated with heart disease, so the elucidation of myosin filament structure to understand the effects of these mutations has a clear and topical clinical relevance.

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“…Helical reconstruction in this case suggested a Class II structure. Modelling of IFM filaments by X-ray diffraction later appeared to support this type of model (AL-Khayat et al 2003).…”

Section: Ideas About Head Conformations In Resting Musclementioning

confidence: 93%

Section: Ideas About Head Conformations In Resting Musclementioning

confidence: 99%

Muscle myosin filaments: cores, crowns and couplings

Squire

2009

Biophys Rev

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“…These data were interpreted as showing that the second head wrapped around the thick filament and bound to the the neck of the adjacent, projecting myosin head where it left the thick filament surface (Al Khayat et al, 2003). This arrangement provided a compelling explanation both for the repeating thick filament shelves in relaxed muscle, and for their disappearance in rigor (in which the 5.6 to 6.4 average head binding per crown means that on average 1.6 to 2.4 of the 'wrapped-around' heads must leave their positions on the thick filament surface).…”

Section: Actin-myosin Interaction and Force Generationmentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

125

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This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vetebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca ++ binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.

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“…Thick filaments are in exact lateral register across the sarcomere, and crossbridges arising from the thick filament match actin target sites on the thin filament (Wray, 1979a;AL-Khayat et al, 2003). Oscillatory contraction in IFM is likely to depend on the precise geometry of thick filaments, and the assembly and maintenance of the structure would need accessory proteins.…”

Section: Introductionmentioning

confidence: 99%

Myofilin, a protein in the thick filaments of insect muscle

Qiu

Brendel

Cunha

et al. 2005

Journal of Cell Science

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Thick filaments in striated muscle are myosin polymers with a length and diameter that depend on the fibre type. In invertebrates, the length of the thick filaments varies widely in different muscles and additional proteins control filament assembly. Thick filaments in asynchronous insect flight muscle have an extremely regular structure, which is likely to be essential for the oscillatory contraction of these muscles. The factors controlling the assembly of thick filaments in insect flight muscle are not known. We previously identified a thick filament core protein, zeelin 1, in Lethocerus flight and non-flight muscles. This has been sequenced, and the corresponding proteins in Drosophila and Anopheles have been identified. The protein has been re-named myofilin. Zeelin 2, which is on the outside of Lethocerus flight muscle thick filaments, has been sequenced and because of the similarity to Drosophila flightin, is re-named flightin. In Drosophila flight muscle, myofilin has a molecular weight of 20 kDa and is one of five isoforms produced from a single gene. In situ hybridisation of Drosophila embryos showed that myofilin RNA is first expressed late in embryogenesis at stage 15, a little later than myosin. Antibody to myofilin labelled the entire A-band, except for the H-zone, in cryosections of flight and non-flight muscle. The periodicity of myofilin in Drosophila flight muscle thick filaments was found to be 30 nm by measuring the spacing of gold particles in labelled cryosections; this is about twice the 14.5 nm spacing of myosin molecules. The molar ratio of myofilin to myosin in indirect flight muscle is 1:2, which is the same as that of flightin. We propose a model for the association of these proteins in thick filaments, which is consistent with the periodicity and stoichiometry. Myofilin is probably needed for filament assembly in all muscles, and flightin for stability of flight muscle thick filaments in adult flies.

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Myosin Head Configuration in Relaxed Insect Flight Muscle: X-Ray Modeled Resting Cross-Bridges in a Pre-Powerstroke State Are Poised for Actin Binding

Cited by 74 publications

References 68 publications

Muscle myosin filaments: cores, crowns and couplings

Muscle myosin filaments: cores, crowns and couplings

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Myofilin, a protein in the thick filaments of insect muscle

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