The cold adaptation of microtubules (MTs) has been experimentally linked to changes in lateral interactions between neighboring protofilaments, yet the underlying atomistic mechanism remains unresolved. To address this, we performed microsecond all-atom molecular dynamics simulations of 14-protofilament MTs constructed in the compacted GDP lattice, enabling us to probe tubulin interactions within the MT lattice and to quantify residue-resolved lateral and longitudinal contact networks as well as C-terminal tail (CTT) dynamics. Our simulations were designed for three systems: (1) wild type, (2) point-mutated, and (3) defected MTs. The setups use identical metrics to deliver testable predictions for lateral stability. We hypothesize that single-residue substitutions and local defects reweight interaction maps at the lateral interface. Building on sequence comparisons of cold-adapted yeast and mesophilic tubulins, we prepared targeted β-tubulin point mutations implicated in cold adaptation. The CTTs of tubulins are disordered, negatively charged regions that are poorly resolved in structural experiments. Contact maps and contact-probability analyses of the wild-type tubulins showed that both α- and β-tubulin CTTs preferentially engage the offset “back” tubulin neighbor, with β-CTTs exhibiting a higher interaction probability than α-CTTs. These asymmetric tail-neighbor interactions are consistent with prior experimental observations that CTT interactions modulate the outward splaying of protofilaments during depolymerization. Collectively, our simulations provide a mechanistic framework for understanding lateral-contact-driven cold adaptation and the dynamic roles of tubulin CTTs in regulating MT behavior.
Mofidi et al. (Sun,) studied this question.