Figure 6. Model for cooperative binding under tension.

(A) Computed lifetime ratios (LRs) with a 4 pN sliding window across 0–13 pN showing that lifetimes from actin-binding domain (ABD) multi-step events are longer than single-step events (mean LR = 3.54). Envelopes represent 90% confidence intervals (CIs), obtained via empirical bootstrapping mean (90% CI = 1.69–9.83). (B) Wild-type ternary lifetimes from multi- and single-step events have similar binding lifetimes (mean LR = 1.15, 90% CI = 0.68–1.78). (C) Upon stable binding with actin, a loaded ABD could enable stronger binding to actin by neighbors by allosteric coupling of involving contacts of the C-terminal extension (CTE) and the H2–H5 bundle. (D) The loaded ternary complex may interact with its neighbor differently than the ABD. Allosteric regulation of the ABD by the other αE-catenin domains, steric effects of the large N–M region, and/or differences in force propagation could prevent rearrangements in the ABD that would enhance its load-bearing capacity.

Figure 6—figure supplement 1. Force-dependent cooperative binding for αE-catenin monomer and ternaryΔH1.

(A) αE-catenin monomer data (mean lifetime ratio [LR] = 3.04, 90% confidence interval [CI] = 1.46–7.73) from multi-step yielded longer binding lifetimes than single-step observations across all force ranges, and particularly at the low-force range. (B) TernaryΔH1 multi-step data show a modest lifetime enhancement over single step (mean LR = 1.69, 90% CI = 1.34–2.15).