Figure 2: Force response of αCM.
From: Force-dependent conformational switch of α-catenin controls vinculin binding
(a) Extension change of αCM recorded at 200 Hz in a typical force cycle experiment. During the stretch phase (force-increase) at a loading rate of 4 pN s−1, an unfolding step was observed at ~5 pN (blue box), and two additional ones occurred at higher forces (~15 pN; red box). Two refolding events, one at ~5 pN with>20 nm and another at ~2 pN with >10 nm, were observed during relaxation (force-decrease). The inset shows that the extension at ~5 pN is reversible. (b) Four force-extension curves recorded in four sequential stretch-relax cycles. The stretch curves are indicated in colour, whereas the relax curves are indicated in grey scale. Unfolding steps are marked by up arrows and refolding steps are marked by down arrows. Data in b are smoothed using 0.05-s time intervals. (c) Stepwise extension fluctuation at constant forces. Raw data are shown in red, and the black lines are fitted states using Hidden Markov method (Methods: ‘Determination of transition rates at constant forces’). (d) Typical force-extension curves obtained from four force cycles for L344P αCM mutant on a single tether. The red up arrow marks the missing ~5 pN unfolding step.
