Fig. 3: Estimating the number of HMMs available for actin interaction from rigor rupture events in ATP-free solution.

a 1. Formation of the rigor bonds between the HMM array and the actin filament. 2. The motor support is moved away first in the direction (z) perpendicular to the plane of the actin–myosin interface and then in the direction (x) parallel to the plane, as indicated by the arrow. Panel modified from Ref. ²³. b Force (F_x, lower record) of an ensemble of soleus HMMs in response to the movement of the nanopositioner away from the actin filament in the x direction (upper record, velocity 50 nm s⁻¹). The small vertical bars indicate the rupture events (force drop completed in less than 50 ms), the last of which corresponds to complete detachment of the actin filament. c Records with the same protocol applied to an ensemble of psoas HMM.