| Summary: | Due to the increasing prevalence of fungal diseases caused by fungi of the genus <i>Candida</i> and the development of pathogen resistance to available drugs, the need to find new effective antifungal agents has increased. Azole antifungals, which are inhibitors of sterol-14α-demethylase or CYP51, have been widely used in the treatment of fungal infections over the past two decades. Of special interest is the study of <i>C. krusei</i> CYP51, since this fungus exhibit resistance not only to azoles, but also to other antifungal drugs and there is no available information about the ligand-binding properties of CYP51 of this pathogen. We expressed recombinant <i>C. krusei</i> CYP51 in <i>E. coli</i> cells and obtained a highly purified protein. Application of the method of spectrophotometric titration allowed us to study the interaction of <i>C. krusei</i> CYP51 with various ligands. In the present work, the interaction of <i>C. krusei</i> CYP51 with azole inhibitors, and natural and synthesized steroid derivatives was evaluated. The obtained data indicate that the resistance of <i>C. krusei</i> to azoles is not due to the structural features of CYP51 of this microorganism, but rather to another mechanism. Promising ligands that demonstrated sufficiently strong binding in the micromolar range to <i>C. krusei</i> CYP51 were identified, including compounds 99 (Kd = 1.02 ± 0.14 µM) and Ch-4 (Kd = 6.95 ± 0.80 µM). The revealed structural features of the interaction of ligands with the active site of <i>C. krusei</i> CYP51 can be taken into account in the further development of new selective modulators of the activity of this enzyme.
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