Identification and evaluation of novel acetolactate synthase inhibitors as antifungal agents

High-throughput phenotypic screening against yeast Saccharomyces cerevisiae revealed a series of triazolo-pyrimidine-sulfonamide compounds with broad-spectrum antifungal activity, no significant cytotoxicity, and low protein binding. To elucidate the target of this series we have applied a chemogenomic profiling approach using the S. cerevisiae deletion collection. All compounds of the series yielded highly similar profiles that suggested acetolactate synthase (Ilv2p, catalyzes the first common step in branched chain amino acid biosynthesis) as a possible target. High correlation to profiles of known Ilv2p inhibitors like chlorimuron-ethyl provided further evidence for a similar mechanism of action. Genome-wide mutagenesis in S. cerevisiae identified 13 resistant clones with 3 different mutations in the catalytic subunit of acetolactate synthase that also conferred cross-resistance to established Ilv2p inhibitors. Mapping the mutations into the published Ilv2p crystal structure outlined...