Structure-Functional Characterization of Cytochrome P450 Sterol 14α-Demethylase (CYP51B) from Aspergillus fumigatus and Molecular Basis for the Development of Antifungal Drugs.
Aspergillus fumigatus is the opportunistic fungal pathogen that predominantly affects the immunocompromised population and causes 600,000 deaths/year. The cytochrome P450 51 (CYP51) inhibitor voriconazole is currently the drug of choice, yet the treatment efficiency remains low, calling for rational development of more efficient agents. A. fumigatus has two CYP51 genes, CYP51A and CYP51B, which share 59% amino acid sequence identity. CYP51B is expressed constitutively, whereas gene CYP51A is reported to be inducible. We expressed, purified, and characterized A. fumigatus CYP51B, including determination of its substrate preferences, catalytic parameters, inhibition, and x-ray structure in complexes with voriconazole and the experimental inhibitor (R)-N-(1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide (VNI). The enzyme demethylated its natural substrate eburicol and the plant CYP51 substrate obtusifoliol at steady-state rates of 17 and 16 min(-1), respectively, but did not metabolize lanosterol, and the topical antifungal drug miconazole was the strongest inhibitor that we identified. The x-ray crystal structures displayed high overall similarity of A. fumigatus CYP51B to CYP51 orthologs from other biological kingdoms but revealed phylum-specific differences relevant to enzyme catalysis and inhibition. The complex with voriconazole provides an explanation for the potency of this relatively small molecule, whereas the complex with VNI outlines a direction for further enhancement of the efficiency of this new inhibitory scaffold to treat humans afflicted with filamentous fungal infections.
From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Tatiana Y
TY
Hargrove
the Synchrotron Research Center, Life Science Collaborative Access Team, Northwestern University, Argonne, Illinois 60439.
Zdzislaw
Z
Wawrzak
Swansea University, Swansea, Wales SA2 8PP, United Kingdom, and.
David C
DC
Lamb
From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
F Peter
FP
Guengerich
From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, the Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232 galina.i.lepesheva@vanderbilt.edu.
Galina I
GI
Lepesheva
D001232:Aspergillus fumigatus / Q000201:enzymology* / Q000235:genetics; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics; D025141:Drug Resistance, Fungal; D005656:Fungal Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D065819:Voriconazole / Q000737:chemistry*
D005656:Fungal Proteins; D003577:Cytochrome P-450 Enzyme System; C465527:cytochrome P-450 CYP51B, Aspergillus; D065819:Voriconazole
Aspergillus; antifungal drugs; cytochrome P450; drug design; enzyme inhibitor; sterol; sterol 14alpha-demethylase (CYP51); x-ray crystallography