Aspergillus fumigatus Mitochondrial Acetyl Coenzyme A Acetyltransferase as an Antifungal Target.

Ergosterol plays an important role in maintaining cell membrane sterol homeostasis in fungi, and as such, it is considered an effective target in antifungal chemotherapy. In yeast, the enzyme acetyl-coenzyme A (CoA) acetyltransferase (ERG10) catalyzes the Claisen condensation of two acetyl-CoA molecules to acetoacetyl-CoA in the ergosterol biosynthesis pathway and is reported as being critical for cell viability. Using yeast ERG10 for alignment, two orthologues, ERG10A (AFUB_000550) and ERG10B (AFUB_083570), were discovered in the opportunistic fungal pathogen Despite the essentiality of ERG10B having been previously validated, the biological function of ERG10A remains unclear. In this study, we have characterized recombinant ERG10A as a functional acetyl-CoA acetyltransferase catalyzing both synthetic and degradative reactions. Unexpectedly, ERG10A localizes to the mitochondria in , as shown by C-terminal green fluorescent protein (GFP) tag fusion. Both knockout and inducible promoter strategies demonstrate that is essential for the survival of The reduced expression of leads to severe morphological defects and increased susceptibility to oxidative and cell wall stresses. Although the catalytic mechanism of acetyl-CoA acetyltransferase family is highly conserved, the crystal structure of ERG10A and its complex with CoA are solved, revealing four substitutions within the CoA binding site that are different from human orthologues. Taken together, our combination of genetic and structural studies demonstrates that mitochondrial ERG10A is essential for cell viability and could be a potential drug target to feed the antifungal drug development pipeline. A growing number of people worldwide are suffering from invasive aspergillosis caused by the human opportunistic fungal pathogen Current therapeutic options rely on a limited repertoire of antifungals. Ergosterol is an essential component of the fungal cell membrane as well as a target of current antifungals. Approximately 20 enzymes are involved in ergosterol biosynthesis, of which acetyl-CoA acetyltransferase (ACAT) is the first enzyme. Two ACATs in are Erg10A and Erg10B. However, the biological function of Erg10A is yet to be investigated. In this study, we showed that Erg10A is localized in the mitochondria and is essential for survival and morphological development. In combination with structural studies, we validated Erg10A as a potential drug target that will facilitate the development of novel antifungals and improve the efficiency of existing drugs.