X-ray evidence for conformational changes in the myosin filaments of vertebrate striated muscle

Haselgrove, John C.

doi:10.1016/0022-2836(75)90094-7

Cited by 283 publications

(251 citation statements)

References 34 publications

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223

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“…This finding suggests that the vertebrate DTNB light chain site is related more to the molluscan Mg*' binding site which is implicated to have a structural role [4], rather than the Ca*+ site which is involved in regulation. It should be emphasized that the present studies do not rule out the existence of some kind of myosin-linked regulation in vertebrate skeletal muscle, whose site of interaction is lost during the extraction of the myosin [6,7], but rather they indicate that the so-called Ca2+ site of the DTNB light chain is not involved, at least on the time scale of activation.…”

Section: Discussioncontrasting

confidence: 83%

“…Vertebrate skeletal myosin itself does not exhibit a Ca2+ sensitive, actinactivated ATPase in vitro in the absence of troponin and tropomyosin [5,6]. Nevertheless it remains plausible that Ca2+ binding to the DTNB light chain initiates the movement of the myosin crossbridges towards the actin filaments [2,3,7] and such an effect might not be revealed by the actomyosin ATPase in the steady-state, particularly in preparations which lack Abbreviations: DTNB light chain, 19 000 dalton subunit dissociated by treatment with 5,5'dithiobis-(2-nitrobenzoate); EGTA, ethyleneglycolbis-(paminoethylether)-N~-tetraacetic acid; EPR, electron paramagnetic resonance 386 the structural integrity of the myofibril. The finding that the DTNB light chain is located near and/or has an effect on the subfragment I-subfragment 2 hinge region appears consistent with the function of controlling crossbridge mobility [8,9].…”

Section: Introductionmentioning

confidence: 99%

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The significance of the slow dissociation of divalent metal ions from myosin ‘regulatory’ light chains

Bagshaw

1977

FEBS Letters

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Section: Discussioncontrasting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The significance of the slow dissociation of divalent metal ions from myosin ‘regulatory’ light chains

Bagshaw

1977

FEBS Letters

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“…Experimentally, the ratio of these axial spacings varies between 0.992 and 1.017 (Huxley & Brown, 1967;Haselgrove, 1975;Squire & Harford, 1988;Craig et al, 1992;Bordas et al, 1993). Since an accurate measurement of the spacings of the 36 and 24nm layer-lines is difficult because of the diffuse nature of the layer-lines, the values cited in these literatures may be consistent with the explanation presented above.…”

Section: Methodssupporting

confidence: 68%

“…1/24.3nm -l (l--9): during contraction (Bordas et al, 1993) and in rigor (Huxley & Brown, 1967;Haselgrove, 1975;Squire & Harford, 1988;Yagi, 1992). Also in an optical diffraction pattern from electron micrographs of rigor muscles (Craig, Alamo & Padron, 1992;Hirose et al, 1993).…”

Section: Methodsmentioning

confidence: 98%

Labelling of Thin Filaments by Myosin Heads in Contracting and Rigor Vertebrate Skeletal Muscles

Yagi¹

1996

Acta Crystallogr D Biol Crystallogr

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A method of crystallographic analysis to identify myosin heads interacting with specific actin sites in vertebrate striated muscles is described. It is based on a Fourier transform of a helix in which probability of occurrence of subunits varies periodically. It predicts the presence of layer-lines at 1/24 and 1/10.4nm -1 which are experimentally observed in contracting and rigor vertebrate striated muscles, showing that the myosin heads are interacting with specific sites on actin but are still maintaining their average 14.5nm axial periodicity.

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“…Millimolar concentrations of Mg2+ or Caz+ were found to promote the association of long S2 [16]. A role for LC2 in this regulation of the head movement has been suggested by Haselgrove [56] and Harrington [57] based on conformational changes induced by Ca2+ binding to LC2 (hydrodynamic studies by Morimoto and Harrington [51] ; X-ray diffraction studies by Hazelgrove [56] and Huxley [58]), although at variance with other studies of the position of the heads with respect to the filament [59]. Our present observations raise the question of whether the positively charged LC1 and LC2 N-terminal segments contribute to the force driving the heads close to the filament backbone in the ordered configuration (and in this case phosphorylation and Caz+ should be considered as effective modulators of the head's attitude) or the only motive element is in the hinge, the observed increased proteolytic susceptibility at the LC1' and LC2" sites being a conformational consequence.…”

Section: Mutual Light Chain Interaction and Light Chain Interacting Sitementioning

confidence: 99%

The proteolytic susceptibility of specific sites in myosin light chains is modulated by the filament conformation

Roulet

Burgat

Cardinaud

1993

European Journal of Biochemistry

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The proteolytic susceptibilities of specific sites in the LC1 and LC2 N-termini were modulated by ionic strength in myosin (a species able to form filaments) but not in S1. (a) In the presence of Ca'+ or Mg", the proteolytic susceptibility (apparent initial reaction rate) showed a sharp discontinuity at a critical ionic concentration similar for LCl', LC2 ' and LC2" cleavages. (b) The susceptibility of LC1' and LC2" was higher at low ionic concentration in the more compact structure of the filament than in the dissociated form at high ionic concentration. (c) The ionic concentration effect was no longer observed with species unable to form filaments. (d) This effect occurred at a critical ionic concentration markedly different from the critical concentration at which the monomer-filament equilibrium was found.These observations lead to the following conclusions. (a) The ionic concentration effect is an attribute of the filament structure. (b) In the filament the faster cleavage at sites (LC1' and LC2") near the LC1 and LC2 N-termini are due to an extended configuration of the N-terminal segment binding to a site in the filament structure. (c) The slower rate of formation of LC2' in the filament indicates that the N-terminal segment of LC2 binds more tightly to the structure than that of LC1. (d) The critical ionic concentration is not that of the filament -monomer equilibrium but corresponds to the order-disorder transition of the heads in the filament. These results suggest that the N-termini of the light chains (here in striated muscles) play a role in a secondary regulatory mechanism. The analysis of these regions may contribute to our understanding of the altered activity and regulation seen in such diseases as idiopathic dilated cardiomyopathy [Margossian, S. S., White, H. D., Caulfield, J. B., Norton, P., Taylor, s. & Slayter, H. s. (1992) Circulation 85, 2720-17331.The central event in muscle contraction is the interaction of actin and myosin in the presence of Mg-ATP. Since the part of myosin which interacts with actin is the head, the complex of actin and S1 is currently considered as a model system of the interaction between actin and myosin. There have been several attempts to solve the structure of this complex [ l , 21. The choice of this model was further supported by the observation that, on S1-coated surfaces, S1 appears to be a sufficient structure to sustain the movement of actin filaments [3], suggesting that the stroke results essentially from a transconformation of the myosin head (review in [4]).However Toyoshima et al. [3] have reported that the sliding velocity was highest with heavy meromyosin (HMM; 6-8 p d s , 30°C) and is only 33-25% of this value with S1. Thus the higher integrated structure found in HMM may be suspected of imparting a better efficiency to the system where a contribution of the S2 hinge segment could be suggested. In myosin thick filament, a more highly integrated system, physiological effectors were observed to govern the position of the heads close to or out fro...

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X-ray evidence for conformational changes in the myosin filaments of vertebrate striated muscle

Cited by 283 publications

References 34 publications

The significance of the slow dissociation of divalent metal ions from myosin ‘regulatory’ light chains

The significance of the slow dissociation of divalent metal ions from myosin ‘regulatory’ light chains

Labelling of Thin Filaments by Myosin Heads in Contracting and Rigor Vertebrate Skeletal Muscles

The proteolytic susceptibility of specific sites in myosin light chains is modulated by the filament conformation

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