{"CAPTION FIG1.png": "'\\n\\n**Figure 1: Talin-1 ABS3 binding to actin is stabilized by force**. (**Ai**) No-load three bead optical trap experimental setup. ABS3 (light blue) is immobilized via an N-terminal HaloTag domain on a microscope coverslip sparsely decorated with 1.5 \\\\(\\\\upmu\\\\)m diameter platform beads. A single actin filament (orange) is stretched between two optically trapped 1 \\\\(\\\\upmu\\\\)m diameter beads. The microscope stage is positioned such that a platform bead is positioned directly underneath the actin filament. (**Aii**) Sample trace of the position of the trapped beads to detect binding of ABS3 to F-actin. In the absence of applied load, ABS3 binding to F-actin can be detected by a damping of high-frequency Brownian fluctuations (cumulative power spectrum, C.P.S. \\\\(>\\\\) 0.3-10 kHz) in the trapped beads. (**Aiii**) Binding lifetimes detected with this method. N=291 binding events detected from sampling the ABS3 construct from 1,419 seconds of recorded data. N=8 binding events detected from sampling an eGFP-coated surface from 2,188 seconds. (**Bi**) Loaded three bead optical trap experimental setup. Same as **Ai**, except the stage is translated parallel to the actin filament in a trapezoidal wave form. (**Bii**) If one or more ABS3 molecules on the platform bead bind to the actin filament while the stage is moving, one of the trapped beads is pulled out of its equilibrium position (demarcated by the blue force trace), thus applying load to the ABS3-F-actin bond. When this occurs the stage motion is halted until all of the protein complexes unbind and the trapped beads return to their equilibrium positions (marked with purple notch, gray trace). Reported lifetimes are last steps of binding events, which for this sample trace is the time between yellow and purple arrows, or the full lifetime of single-step events.\\n\\n'", "CAPTION FIG2.png": "'\\n\\n**Figure 2:****Talin-1 forms a catch bond with F-actin when force is applied towards the pointed end of the actin filament (A)** An asymmetry in bond lifetimes is observed for a single actin filament. (**Ai, Aii**) Load on the _right_ (**Ai**) or _left_ (**Aii**) trapped bead. (**Aiii**) Sample force trace. Load on the right bead is indicated in orange, while load on the left bead is shown in blue. (**B**) (**Bi**) A myosin VI construct steps along actin filaments, pulling the bead attached to the (-) end of the filament out of the trap. (**Bii**) Sample myosin trace. In this example, the left bead is attached to the F-actin (-) end. (**C**) ABS3 binding dwell times measured as a function of force. Forces directed towards the pointed (-) end of the filament correspond to negative force values and forces directed towards the barbed (+) end correspond to positive force values. _Dark gray_: binding lifetimes of events measured in the directionality assay in which the actin filament polarity was explicitly measured for each dumbbell (N=2 flow cells, N=3 dumbbells, N=47 events). _Lavender_: binding dwell times for which the actin filament polarity was statistically inferred. _Orange_: mean dwell times (20 data points per bin), with 95% confidence intervals shown in thinner lines (N = 777 binding events, N=42 dumbbells, N=18 flow cells). (**D**) Fold-difference in bond lifetime for forces applied towards the pointed vs. barbed end of the actin filament, with 95% confidence intervals per 1 pN bin.\\n\\n'", "CAPTION FIG3.png": "'\\n\\n**Figure 3: The C-terminal dimerization domain (DD) is required for F-actin binding under load. (A)** The constructs used in this study (see text). (B) Native PAGE of BSA (MW=66.5 as monomer), ABS3 (64.2 kDa if monomeric), ABS3\\\\(\\\\Delta\\\\)DD (58.5 kDa, monomer) and NTD-ABS3\\\\(\\\\Delta\\\\)DD (113 kDa). Note the gradual shift in apparent molecular weight as a function of ABS3 concentration, suggestive of a dynamic equilibrium of dimerization. \\\\(\\\\bullet\\\\) and \\\\(\\\\overline{\\\\textbf{V}}\\\\)denote distances traveled of peaks in different replicates. (C) Actin cosedimentation of 4 uM ABS3, 2 uM NTD-ABS3, or 2 uM NTD-ABS3\\\\(\\\\Delta\\\\)DD with 20 uM actin. N=3 replicates. (D) Force-lifetime plots of binding events detected for the NTD-ABS3 construct (lavender) with mean lifetime and confidence intervals on the mean plotted in orange (20 data points per bin). N=386 binding events, N=18 dumbbells, N=8 flow cells.\\n\\n'", "CAPTION FIG4.png": "'Figure 4: Talin ABS3 functions as a molecular AND gate (see text). Integrin cartoon modified from Zhu _et al._, 2017.\\n\\n'"}