Crossbridge behaviour during muscle contraction

Huxley, H. E.; Kress, M.

doi:10.1007/bf00713057

Cited by 238 publications

(165 citation statements)

References 25 publications

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“…Therefore, we believe our findings provide a quantitative estimate of the change in tail orientation associated with an increase in S1 force based on noninvasive measurements in living cells and a rotating tail model of S1 action (1,(17)(18)(19).…”

Section: Discussionmentioning

confidence: 74%

“…Since 1969, the proposed power stroke mechanism has been the generation of a torque by rotation of some portion of S1 about its point of attachment to actin, producing an unloaded filament sliding of Ϸ10 nm or an isometric force of 1-5 pN (1,(17)(18)(19). However, until recently, attempts to detect this rotation in situ have produced equivocal results.…”

Section: Discussionmentioning

confidence: 99%

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Changes in myosin S1 orientation and force induced by a temperature increase

Griffiths

Bagni²,

Colombini³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Section: Discussionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Changes in myosin S1 orientation and force induced by a temperature increase

Griffiths

Bagni²,

Colombini³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…Comprehensive mechanisms require a structural identity for their kinetic intermediates. Our kinetic scheme resembles mechanisms in which myosin heads are enabled by movement to generate tension after an L-jump, a class of model first proposed by Huxley and Kress in the mid 1980s (44). We find a compelling match between our kinetics and a structural mechanism based on 3D images of individual attached crossbridges obtained from electron micrographs of flash-frozen contracting insect flight muscle (33).…”

Section: L-jump Kinetics and The Cross-bridge Cyclesupporting

confidence: 63%

Mechanistic role of movement and strain sensitivity in muscle contraction

Davis

Epstein

2009

Proc. Natl. Acad. Sci. U.S.A.

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Tension generation can be studied by applying step perturbations to contracting muscle fibers and subdividing the mechanical response into exponential phases. The de novo tension-generating isomerization is associated with one of these phases. Earlier work has shown that a temperature jump perturbs the equilibrium constant directly to increase tension. Here, we show that a length jump functions quite differently. A step release (relative movement of thick and thin filaments) appears to release a steric constraint on an ensemble of noncompetent postphosphate release actomyosin cross-bridges, enabling them to generate tension, a concentration jump in effect. Structural studies [Taylor KA, et al. (1999) Tomographic 3D reconstruction of quick-frozen, Ca 2؉ -activated contracting insect flight muscle. Cell 99:421-431] that map to these kinetics indicate that both catalytic and lever arm domains of noncompetent myosin heads change angle on actin, whereas lever arm movement alone mediates the power stroke. Together, these kinetic and structural observations show a 13-nm overall interaction distance of myosin with actin, including a final 4-to 6-nm power stroke when the catalytic domain is fixed on actin. Raising fiber temperature with both perturbation techniques accelerates the forward, but slows the reverse rate constant of tension generation, kinetics akin to the unfolding/folding of small proteins. Decreasing strain, however, causes both forward and reverse rate constants to increase. Despite these changes in rate, the equilibrium constant is strain-insensitive. Activation enthalpy and entropy data show this invariance to be the result of enthalpyentropy compensation. Reaction amplitudes confirm a strain-invariant equilibrium constant and thus a strain-insensitive ratio of pretension-to tension-generating states as work is done.enthalpy-entropy compensation ͉ length step ͉ non-Arrhenius ͉ protein folding ͉ tension generation T he question of how the many asynchronously operating myosin motors generate tension and movement in muscle fibers is a critical issue in biology. Two different mechanisms have been proposed. In one, thermal fluctuations in position enable myosin heads (cross-bridges) to bind actin in a strained configuration to generate tension (1, 2). This rectification process can occur between detached and attached heads or by heads changing angle between subsites while attached to actin. For these thermal ratchet models to function at physiological rates, a sequence of multiple attached states is generally required, the stiffer the cross-bridge the larger the number of states. Heterogeneous mechanisms, some with sequential temperature-sensitive and -insensitive tension-generating transitions, have also been invoked (3-5). Power stroke mechanisms in which tension generation occurs as a single-step conformational change in attached cross-bridges offer an alternative mechanism e.g. (6-10). Other important aspects include the relationship between intermediate states of the ATPase cycle and tension generation....

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“…[17][18][19] Therefore, the relative frequency of cross-bridges appears correlated with the percentage of unphosphorylated MyBP-C and the degree of myocardial segment shortening (Figure 3). The average periodicity for cross-bridges in the myofibrils of sham-operated and ischemic hearts was 34 and 42 nm, respectively.…”

Section: Discussionmentioning

confidence: 94%

Myosin-Binding Protein C Phosphorylation, Myofibril Structure, and Contractile Function During Low-Flow Ischemia

Decker

Kulikovskaya

et al. 2005

Circulation

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Background-Contractile dysfunction develops in the chronically instrumented canine myocardium after bouts of low-flow ischemia and persists after reperfusion. The objective of this study is to identify whether changes in the phosphorylation state of myosin-binding protein C (MyBP-C) are a potential cause of dysfunction. Methods and Results-During low-flow ischemia, MyBP-C is dephosphorylated, and the number of actomyosin cross-bridges in the central core of the sarcomere decreases as thick filaments dissemble from the periphery of the myofibril. During reperfusion, MyBP-C remains dephosphorylated, and its degradation is accelerated. Conclusions-Dephosphorylation of MyBP-C may initiate changes in myofibril thick filament structure that decrease the interaction of myosin heads with actin thin filaments. Limiting the formation of actomyosin cross-bridges may contribute to the contractile dysfunction that is apparent after low-flow ischemia.

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Crossbridge behaviour during muscle contraction

Cited by 238 publications

References 25 publications

Changes in myosin S1 orientation and force induced by a temperature increase

Changes in myosin S1 orientation and force induced by a temperature increase

Mechanistic role of movement and strain sensitivity in muscle contraction

Myosin-Binding Protein C Phosphorylation, Myofibril Structure, and Contractile Function During Low-Flow Ischemia

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