Crystal structures of full-length lanosterol 14α-demethylases of prominent fungal pathogens candida albicans and candida glabrata provide tools for antifungal discovery

Abstract

Targeting lanosterol 14α-demethylase (LDM) with azole drugs provides prophylaxis and treatments for superficial and disseminated fungal infections, but cure rates are not optimal for immunocompromised patients and individuals with comorbidities. The efficacy of azole drugs has also been reduced due to the emergence of drug-resistant fungal pathogens. We have addressed the need to improve the potency, spectrum, and specificity for azoles by expressing in Saccharomyces cerevisiae functional, recombinant, hexahistidine-tagged, full-length Candida albicans LDM (CaLDM6XHis) and Candida glabrata LDM (CgLDM6XHis) and determining their X-ray crystal structures. The crystal structures of CaLDM6XHis, CgLDM6XHis, and ScLDM6XHis have the same fold and bind itraconazole in nearly identical conformations. The catalytic domains of the full-length LDMs have the same fold as the CaLDM6XHis catalytic domain in complex with posaconazole, with minor structural differences within the ligand binding pocket. Our structures give insight into the LDM reaction mechanism and phenotypes of single-site CaLDM mutations. This study provides a practical basis for the structure-directed discovery of novel antifungals that target LDMs of fungal pathogens.