Molecular simulations of paclitaxel binding to mutant β-tubulin: insights into chemotherapy resistance.

Paclitaxel, a cornerstone in cancer chemotherapy, stabilizes microtubules by binding to the β-tubulin taxane site. However, resistance mechanisms, often driven by β-tubulin mutations, undermine its efficacy. While such mutations are known to alter drug sensitivity, their molecular impact on paclitaxel binding remains incompletely understood. Here, we employ molecular docking, molecular dynamics (MD) simulations, and Molecular Mechanics with Generalized Born Surface Area (MM/GBSA) calculations to quantify how clinically relevant β-tubulin mutations affect paclitaxel binding affinity. Root mean square fluctuation (RMSF) analysis was used to assess local structural dynamics near the binding site. Our results show that despite minor variations in docking scores, MM/GBSA analyses revealed significant mutation-induced shifts in binding free energy, particularly for residues near the M loop, H5-H6 helices, and S9-S10 region. Complementary RMSF analysis indicated altered flexibility in several of these regions, suggesting potential disruptions to local stabilization mechanisms. Differences between single- and two-dimer simulations highlight the importance of modeling lateral protofilament contacts when evaluating microtubule-targeting agents. These findings underscore the relevance of structure-based modeling for understanding drug resistance mechanisms and informing the development of mutation-aware taxane therapies.