Fig. 5: Mechanical stability of partial α-actinin 1 homo-dimer of SR2–SR3–SR4:SR1–SR2–SR3 under shear–force geometry.

a–d Representative force--bead height curves of partial α-actinin 1 rod homo-dimer of SR2–SR3–SR4:SR1–SR2–SR3 under shear–force geometry during force-increase scans (5 pN s⁻¹). Four distinct rupture behaviors were plotted in right panels (a–d), respectively. The distinct rupture events are indicated by different colored (red, blue, magenta, orange) arrows. Left panels: illustrations of possible conformational changes of partial dimers associated with different pairing states. The colored dashed lines in the left panels indicate the height jump when the rupture event occurs. e The force–step size graph of the rupture events of SR2–SR3–SR4:SR1–SR2–SR3 dimer during force-increase scans. the four colored dashed lines are the theoretically predicated force-dependent stepsizes assuming the concurrent rupturing and unfolding of all the three SR domains (red), with two SR domains (blue), with one SR domains (magenta), or without SR domain (orange), respectively. N = 128 (red), 64 (blue), 101 (magenta) and 51 (orange). f The normalized rupture force distribution of the SR2–SR3–SR4:SR1–SR2–SR3 dimer during force-increase scans. The lines are gaussian fitting curves of the distributions, with the peak values as 32.5 ± 0.3 pN (red), 22.2 ± 0.2 pN (blue), 16.1 ± 0.2 pN and 9.4 ± 0.3 pN (magenta), 10.8 ± 0.5 pN and 3.6 ± 0.2 pN (orange) respectively. g Top panel: The illustration of the experimental design for quantifying the force-dependent lifetime of the partial dimer. Bottom panel shows the representative time–bead height curves of the partial dimer at an example target force of 26 pN. h The force-dependent lifetime of the α-actinin 1 partial dimer of SR2–SR3–SR4:SR1–SR2–SR3 under shear–force geometry. Colored hollow symbols and solid symbols are the individual dwell times of the dimer and the characteristic lifetime of the dimer at each force, respectively. Three clustered force-dependent lifetime relations were obtained indicated by three colored symbols, respectively. Two sets of the lifetime were fitted with Bell Model (red and blue colored lines, respectively) to obtain the corresponding k₀ and Δ. The magenta data set was not fitted due to limited data obtained. Source data are provided as a Source Data file.