TY - JOUR
T1 - Amino acid variations of cytochrome P-450 lanosterol 14α-demethylase (CYP51A1) from fluconazole-resistant clinical isolates of Candida albicans
AU - Manavathu, Elias K.
AU - Kallakuri, Srinivasu
AU - Arganoza, María T.
AU - Vazquez, Jose Antonio
PY - 1999/12/1
Y1 - 1999/12/1
N2 - We studied six clinical isolates of Candida albicans. All six isolates showed high level resistance to fluconazole (minimum inhibitory concentrations 64 μg/ml) with varying degrees of cross-resistance to other azoles but not to amphotericin B. Neither higher dosage nor upregulation of the gene encoding the cytochrome P450 lanosterol 14 α-demethylase (CYP51A1 or P-450LDM) was responsible for fluconazole resistance. The resistant and the susceptible isolates accumulated similar amounts of azoles. To examine whether resistance to fluconazole in these clinical isolates of C. albicans is mediated by an altered target of azole action, we cloned the structural gene encoding P-450LDM from the fluconazole-resistant isolates. The amino acid sequences of the P-450LDMs from the isolates were deduced from the gene sequences and compared to the P-450LDM sequence of the fluconazole- susceptible C. albicans B311. The enzymes from the clinical isolates showed 2 to 7 amino acid variations scattered across the molecules encompassing 10 different loci. One-half of the amino acid changes obtained were conserved substitutions (E116D, K143R, E266D, D278E, R287K) compared to the susceptible strain. Non-conserved substitutions were T128K, R267H, S405F, G450E and G464S, three of which are in and around the heme-binding region of the molecule. R287K is the only amino acid change that was found in all six clinical isolates. One or more of these mutational alterations may lead to the expression of an azole-resistant enzyme.
AB - We studied six clinical isolates of Candida albicans. All six isolates showed high level resistance to fluconazole (minimum inhibitory concentrations 64 μg/ml) with varying degrees of cross-resistance to other azoles but not to amphotericin B. Neither higher dosage nor upregulation of the gene encoding the cytochrome P450 lanosterol 14 α-demethylase (CYP51A1 or P-450LDM) was responsible for fluconazole resistance. The resistant and the susceptible isolates accumulated similar amounts of azoles. To examine whether resistance to fluconazole in these clinical isolates of C. albicans is mediated by an altered target of azole action, we cloned the structural gene encoding P-450LDM from the fluconazole-resistant isolates. The amino acid sequences of the P-450LDMs from the isolates were deduced from the gene sequences and compared to the P-450LDM sequence of the fluconazole- susceptible C. albicans B311. The enzymes from the clinical isolates showed 2 to 7 amino acid variations scattered across the molecules encompassing 10 different loci. One-half of the amino acid changes obtained were conserved substitutions (E116D, K143R, E266D, D278E, R287K) compared to the susceptible strain. Non-conserved substitutions were T128K, R267H, S405F, G450E and G464S, three of which are in and around the heme-binding region of the molecule. R287K is the only amino acid change that was found in all six clinical isolates. One or more of these mutational alterations may lead to the expression of an azole-resistant enzyme.
KW - C. albicans
KW - Demethylase
KW - Fluconazole
KW - Resistance
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M3 - Article
C2 - 18473547
AN - SCOPUS:0033369251
SN - 1130-1406
VL - 16
SP - 198
EP - 203
JO - Revista Iberoamericana de Micologia
JF - Revista Iberoamericana de Micologia
IS - 4
ER -