Azole resistance: Insights from Y132 substitutions inCandidasterol 14α-demethylase

Background Azole-resistant Candida infections are on the rise. Resistant substitutions at Y132 in sterol 14α-demethylase, the key target of azole drugs, are frequent. However, it is unclear why only some Y132 substitutions are favoured or how they exert differential effects on different azoles. Materials and Methods Reported instances of Y132 substitutions were collected from the literature. Extensive molecular dynamics simulations of sterol 14α-demethylase bound to fluconazole or VT1161 (VT1) were performed, and the ligand-binding free energies were computed to quantify the effects of various Y132 substitutions on azole binding/interactions. Results Three azole-resistant substitutions, Y to C/F/H, were reported at residue position 132 in sterol 14α-demethylase. The Y132H was the most common substitution in C. albicans , while it was Y132F in other species. Ligand-binding free energies were -13.81 kcal/mol and -35.04 kcal/mol for fluconazole and VT1, respectively. There were differences in the ligand-binding free energies after substitutions compared to the wild type protein. Conclusion Y132F and Y132H were the most frequent substitutions in Candida sterol 14α-demethylase. Far higher binding free energy of fluconazole in comparison with VT1 might partly explain its susceptibility to azole-resistant substitutions. The results give key insights into azole resistance, and antifungal drug discovery and optimization.