Complementation of a Saccharomyces cerevisiae ERG11/CYP51 (sterol 14α-demethylase) doxycycline-regulated mutant and screening of the azole sensitivity of Aspergillus fumigatus isoenzymes CYP51A and CYP51B.

Aspergillus fumigatus sterol 14α-demethylase isoenzymes CYP51A and CYP51B were heterologously expressed in a Saccharomyces cerevisiae mutant (YUG37-erg11), wherein native ERG11/CYP51 expression is controlled using a doxycycline-regulatable promoter. When cultured in the presence of doxycycline, recombinant YUG37-pcyp51A and YUG37-pcyp51B yeasts were able to synthesize ergosterol and grow; a control strain harboring reverse-oriented cyp51A could not. YUG37-pcyp51A and YUG37-pcyp51B constructs showed identical sensitivity to itraconazole, posaconazole, clotrimazole, and voriconazole. Conversely, YUG37-pcyp51A withstood 16-fold-higher concentrations of fluconazole than YUG37-pcyp51B (8 and 0.5 μg ml⁻¹, respectively).