Conformation of the myosin motor during force generation in skeletal muscle

Irving, Malcolm; Piazzesi, Gabriella; Lucii, L; Sun, Yin-Biao; Harford, Jeffrey J.; Dobbie, Ian M.; Ferenczi, Michael A.; Reconditi, Massimo; Lombardi, Vincenzo

doi:10.1038/75890

Cited by 100 publications

(39 citation statements)

References 26 publications

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“…2a, T 1 , green circles) and decreased further during the phase 2 force recovery (T 2 , blue circles). The width of the intensity distribution of the M3 reflection along the axis perpendicular to the muscle fiber was not affected by the stretch by Ͼ10%, as shown previously for releases (21), confirming that the I M3 changes after a step are not influenced by changes in lateral filament alignment. The intensity profile of the M3 reflection along the axis parallel to the muscle fiber (Fig.…”

Section: X-ray Diffraction Changes Aftersupporting

confidence: 64%

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Skeletal muscle resists stretch by rapid binding of the second motor domain of myosin to actin

Brunello

Reconditi²,

Elangovan³

et al. 2007

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

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104

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A shortening muscle is a machine that converts metabolic energy into mechanical work, but, when a muscle is stretched, it acts as a brake, generating a high resistive force at low metabolic cost. The braking action of muscle can be activated with remarkable speed, as when the leg extensor muscles rapidly decelerate the body at the end of a jump. Here we used time-resolved x-ray and mechanical measurements on isolated muscle cells to elucidate the molecular basis of muscle braking and its rapid control. We show that a stretch of only 5 nm between each overlapping set of myosin and actin filaments in a muscle sarcomere is sufficient to double the number of myosin motors attached to actin within a few milliseconds. Each myosin molecule has two motor domains, only one of which is attached to actin during shortening or activation at constant length. A stretch strains the attached motor domain, and we propose that combined steric and mechanical coupling between the two domains promotes attachment of the second motor domain. This mechanism allows skeletal muscle to resist external stretch without increasing the force per motor and provides an answer to the longstanding question of the functional role of the dimeric structure of muscle myosin.motor proteins ͉ myosin II S keletal muscle primarily acts as a machine that uses metabolic energy to drive macroscopic movements of the body. When an active muscle shortens, the force decreases, mechanical work is done, and ATP is hydrolyzed at a faster rate. However, skeletal muscle can also act as a brake to resist a sudden increase in load. When an active muscle is lengthened, the force increases (1), work is done on the muscle, and the rate of ATP hydrolysis decreases (2-4). The braking action of muscle is a matter of everyday experience, for example, when the extensor muscles of the legs have to oppose the momentum of the body when walking downstairs or landing at the end of a jump.The molecular basis of the braking action of muscle is unknown. Muscle fibers become stiffer during a stretch (5), provided that the length change is distributed uniformly along the fiber (6-9), suggesting that force enhancement by stretch is related to the presence of an additional elastic structure. Because fiber stiffness during isometric contraction depends on myosin motors cross-linking the arrays of myosin and actin filaments in each muscle sarcomere, the stretch response might be due to recruitment of additional myosin motors. Alternatively, resistance to stretch could be due to other protein components; cytoskeletal proteins, for example, might become taut during the stretch. Whatever its molecular basis, the response must be activated during the stretch itself, i.e., on the millisecond timescale in the case of an extensor muscle during landing of the body after a jump. We therefore focused on the mechanical and structural changes in the muscle within the first few milliseconds after a rapid (120 s) stretch imposed on an isolated intact muscle fiber during isometric contraction. Using a com...

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Section: X-ray Diffraction Changes Aftersupporting

confidence: 64%

“…The decrease in I M3 is caused by tilting of the motors, which broadens their mass distribution along the filament axis (21,23,24); the increase in R M3 results from the increase in the interference distance between the two arrays of motors in each filament as they tilt away from the sarcomeric M line (18,25) (Fig. 1c).…”

Section: X-ray Diffraction Changes Aftermentioning

confidence: 99%

Skeletal muscle resists stretch by rapid binding of the second motor domain of myosin to actin

Brunello

Reconditi²,

Elangovan³

et al. 2007

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

Self Cite

104

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“…1, providing an excellent confirmation of the tilting cross-bridge theory. Similar experiments with much improved time resolution, 0.1 ms, have confirmed the earlier findings [9]. In all these experiments, gas-filled multiwire proportional chambers were used to record the diffraction patterns.…”

Section: Time-resolved Muscle Diffractionsupporting

confidence: 70%

Potential impact of silicon pixel detectors on structural biology

Faruqi

2009

Nuclear Instruments and Methods in Physics Research Section A:

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“…Neither the known crystal structures of the myosin head nor cryo-electron microscopy with reconstruction of the actomyosin complex have resolved this question. Some authors considered elastic bending of the long, light-chain-binding ␣-helix an obvious candidate (4,9,10). The actin-myosin interface (11) or the junction between the lightchain domain and the catalytic domain of the myosin head (9) as well as subfragment 2 were also considered (12) as other possibilities for the location of elastic distortion.…”

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confidence: 99%

Mutation of the myosin converter domain alters cross-bridge elasticity

Köhler

Winkler²,

Schulte³

et al. 2002

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

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Elastic distortion of a structural element of the actomyosin complex is fundamental to the ability of myosin to generate motile forces. An elastic element allows strain to develop within the actomyosin complex (cross-bridge) before movement. Relief of this strain then drives filament sliding, or more generally, movement of a cargo. Even with the known crystal structure of the myosin head, however, the structural element of the actomyosin complex in which elastic distortion occurs remained unclear. To assign functional relevance to various structural elements of the myosin head, e.g., to identify the elastic element within the cross-bridge, we studied mechanical properties of muscle fibers from patients with familial hypertrophic cardiomyopathy with point mutations in the head domain of the ␤-myosin heavy chain. We found that the Arg-719 3 Trp (Arg719Trp) mutation, which is located in the converter domain of the myosin head fragment, causes an increase in force generation and fiber stiffness under isometric conditions by 48 -59%. Under rigor and relaxing conditions, fiber stiffness was 45-47% higher than in control fibers. Yet, kinetics of active cross-bridge cycling were unchanged. These findings, especially the increase in fiber stiffness under rigor conditions, indicate that cross-bridges with the Arg719Trp mutation are more resistant to elastic distortion. The data presented here strongly suggest that the converter domain that forms the junction between the catalytic and the light-chain-binding domain of the myosin head is not only essential for elastic distortion of the cross-bridge, but that the main elastic distortion may even occur within the converter domain itself. It is widely accepted that active force and movement generated by muscle fibers result from structural changes in the head domain of the myosin molecule (the cross-bridge) while it is attached to the actin filament. These changes are thought to involve a tilting of the light-chain-binding domain of the myosin head relative to its catalytic domain (1-7). As a result of such structural changes distortion of an elastic element within the actin-attached myosin head allows strain to develop before movement (8). Relief of this strain drives sliding of actin filaments past the myosin filaments, or alternatively, if filament sliding is prevented, active force is generated because of continued strain of the elastic element. Despite the central significance of this concept, however, it remained unclear which part of the actomyosin complex represents the elastic element-i.e., the element that experiences the main elastic distortion while other parts act more like rigid bodies. Neither the known crystal structures of the myosin head nor cryo-electron microscopy with reconstruction of the actomyosin complex have resolved this question. Some authors considered elastic bending of the long, light-chain-binding ␣-helix an obvious candidate (4, 9, 10). The actin-myosin interface (11) or the junction between the lightchain domain and the catalytic domain of the...

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Conformation of the myosin motor during force generation in skeletal muscle

Cited by 100 publications

References 26 publications

Skeletal muscle resists stretch by rapid binding of the second motor domain of myosin to actin

Skeletal muscle resists stretch by rapid binding of the second motor domain of myosin to actin

Potential impact of silicon pixel detectors on structural biology

Mutation of the myosin converter domain alters cross-bridge elasticity

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