Exploring force-driven stochastic folding dynamics in mechano-responsive proteins and implications in phenotypic variation.

Single-point mutations are pivotal in molecular zoology, shaping functions and influencing genetic diversity and evolution. Here we study three such genetic variants of a mechano-responsive protein, cadherin-23, that uphold the structural integrity of the protein, but showcase distinct genotypes and phenotypes. The variants exhibit subtle differences in transient intra-domain interactions, which in turn affect the anti-correlated motions among the constituent β-strands. In nature, the variants experience declining functions with aging at different rates. We expose these variants to constant and oscillatory forces using magnetic tweezer, and measure variations in stochastic folding dynamics. All variants exhibit multiple microstates under force. However, the protein variant with higher number of intra-domain interactions exhibits transitions among the heterogeneous microstates for larger extent of forces and persisted longer. Conversely, the protein variant with weaker inter-strand correlations exhibits greater unfolding cooperativity and faster intrinsic folding, although its folding-energy landscape is more susceptible to distortion under tension. Our study thus deciphers the molecular mechanisms underlying the variations in force-adaptations and proposes a mechanical relation between genotype and phenotype.