Mechanics of myosin function in white muscle fibres of the dogfish, Scyliorhinus canicula

Key points Muscle force and shortening are generated by a structural change called the working stroke in myosin motor proteins that cross-link the myosin and actin filaments in muscle. Precise values for two key parameters of the myosin motor its mechanical stiffness and the size of the working stroke at low load were previously only available from one type of muscle in one species, fast twitch muscles of the frog, so it was not clear how generally applicable these values were. We show that in dogfish fast muscle the low-load working stroke is the same as in frog muscle, but the myosin motor stiffness is smaller. The results provide new insights into how the molecular properties of myosin motors in different muscle types and species may be adapted for different muscle functions.