| Fluconazole is an antifungal agent used to treat fungal infections. Candida krusei---inherently resistant to fluconazole---is of concern due to its emergence as an invasive infectious agent. Resistance to fluconazole in C. krusei is associated with reduced susceptibility of the enzyme cytochrome P450 sterol 14alpha-demethylase (CYP51) to inhibition by the antifungal agent.; We compared the amino acid sequence of C. krusei CYP51 (ckCYP51) to fluconazole-susceptible strain of Candida albicans (caCYP51). Site-directed mutagenesis used changed amino acids differences between the sensitive caCYP51 and resistant ckCYP51. The fluconazole susceptibility of S. cerevisiae expressing these candidal CYP51s was determined by measuring the minimum inhibitory concentration (MIC).; Yeast expressing wild type ckCYP51 had fluconazole MIC, 256mug/ml, whereas caCYP51 was 32mug/ml. MIC for yeast expressing the mutant ckCYP51 containing amino acid substitutions L113F, W145K, S315A, and T512V was 256mug/ml. These amino acid substitutions did not increase susceptibility of C. krusei to fluconazole. |
