The molecular structural basis of the braking action of muscle

Abstract

Skeletal muscles generate force and shortening through a structural powerstroke in actin-bound myosin motors linked to ATP hydrolysis, but they also act as brakes to resist stretching by an external load. The molecular structural basis of muscle braking has remained obscure. Here we show that muscle braking is driven both by structural changes in myosin motors and by distortion of the lattice of thick and thin filaments including their M-band and Z-disk connections. A strained motor conformation is established early during stretch, but force continues to increase as thin filaments are displaced from their symmetrical lattice positions, the lateral shear between thick filaments increases, and the lattice volume decreases. Moreover, whilst the motor conformation rapidly recovers after the stretch, the distortion of the filament lattice is largely maintained, storing the work done on the muscle during stretch and accounting for the residual force enhancement after stretch.

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BibTeX

@misc{hill2026molecular,
  title = {{The molecular structural basis of the braking action of muscle}},
  author = {C. Hill and M. Kalakoutis and A. Arcidiacono and A. Fukutani and T. Narayanan and E. Brunello and L. Fusi and M. Irving},
  howpublished = {bioRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.25.753934},
  url = {https://www.biorxiv.org/content/10.64898/2026.09.25.753934v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - The molecular structural basis of the braking action of muscle
AU  - C. Hill
AU  - M. Kalakoutis
AU  - A. Arcidiacono
AU  - A. Fukutani
AU  - T. Narayanan
AU  - E. Brunello
AU  - L. Fusi
AU  - M. Irving
PY  - 2026
DA  - 2026/09/25
PB  - bioRxiv
DO  - 10.64898/2026.09.25.753934
UR  - https://www.biorxiv.org/content/10.64898/2026.09.25.753934v1
AB  - Skeletal muscles generate force and shortening through a structural powerstroke in actin-bound myosin motors linked to ATP hydrolysis, but they also act as brakes to resist stretching by an external load. The molecular structural basis of muscle braking has remained obscure. Here we show that muscle braking is driven both by structural changes in myosin motors and by distortion of the lattice of thick and thin filaments including their M-band and Z-disk connections. A strained motor conformation is established early during stretch, but force continues to increase as thin filaments are displaced from their symmetrical lattice positions, the lateral shear between thick filaments increases, and the lattice volume decreases. Moreover, whilst the motor conformation rapidly recovers after the stretch, the distortion of the filament lattice is largely maintained, storing the work done on the muscle during stretch and accounting for the residual force enhancement after stretch.
ER  -

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