Formation of azole-resistant Candida albicans by mutation of sterol 14-demethylase P450.
The sterol 14-demethylase P450 (CYP51) of a fluconazole-resistant isolate of Candida albicans, DUMC136, showed reduced susceptibility to this azole but with little change in its catalytic activity. Twelve nucleotide substitutions, resulting in four amino acid changes, were identified in the DUMC136 CYP51 gene in comparison with a reported CYP51 sequence from a wild-type, fluconazole-susceptible C. albicans strain. Seven of these substitutions, including all of those causing amino acid changes, were located within a region covering one of the putative substrate recognition sites of the enzyme (SRS-1). Polymorphisms within this region were observed in several C. albicans isolates, and some were found to be CYP51 heterozygotes. Among the amino acid changes occurring in this region, only an alteration of Y132 was common among these fluconazole-resistant isolates, which suggests the importance of this residue to the fluconazole resistance of the target enzyme. DUMC136 and another fluconazole-resistant isolate were homozygotes with respect to CYP51, although the typical wild-type, fluconazole-susceptible C. albicans was a CYP51 heterozygote. These findings suggest that part of the fluconazole-resistant phenotype of C. albicans DUMC136 was acquired through a mutation-prone area of CYP51, an area which might promote the formation of fluconazole-resistant CYP51, along with a mechanism(s) which allows the formation of a homozygote of this altered CYP51 in this diploid pathogenic yeast.
Asai
K
K
Pharmaceutical Research Division, Pharmacology Laboratories, Takeda Chemical Industries, Ltd., Yodogawa-ku, Osaka 532, Japan. asai_kentaro@takeda.co.jp
Tsuchimori
N
N
Okonogi
K
K
Perfect
J R
JR
Gotoh
O
O
Yoshida
Y
Y
D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics*; D058886:Sterol 14-Demethylase
D000935:Antifungal Agents; D001393:Azoles; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase