The Aspergillus fumigatus dihydroxyacid dehydratase Ilv3A/IlvC is required for full virulence

• Published in: PloS one Vol. 7; no. 9; p. e43559
• Main Authors: Oliver, Jason D, Kaye, Sarah J, Tuckwell, Danny, Johns, Anna E, Macdonald, Darel A, Livermore, Joanne, Warn, Peter A, Birch, Mike, Bromley, Michael J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.09.2012; Public Library of Science (PLoS)
• Subjects: Acids; Amino Acid Sequence; Amino acids; Amino Acids, Branched-Chain - biosynthesis; Analysis; Animal models; Animals; Antifungal agents; Aspergillosis - microbiology; Aspergillus; Aspergillus fumigatus; Aspergillus fumigatus - enzymology; Aspergillus fumigatus - genetics; Aspergillus fumigatus - pathogenicity; Aspergillus nidulans; Aspergillus niger; Bacteria; Bioinformatics; Biology; Biosynthesis; Biosynthetic Pathways; Candida albicans; Candida glabrata; Chain branching; Chains; Cryptococcus neoformans; Dehydration; Enzyme Activation; Enzymes; Eukaryotes; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Fungicides; Genes; Genetic aspects; Homology; Hydro-Lyases - chemistry; Hydro-Lyases - genetics; Hydro-Lyases - metabolism; Infections; Isoleucine; Male; Medicine; Mice; Mitochondrial Proteins - chemistry; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; Molecular Sequence Data; Mutants; Mutation; Oxidoreductases; Phylogenetics; Phylogeny; Physiological aspects; Plants (botany); Proteins; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Saccharomyces cerevisiae; Sequence Alignment; Valine; Virulence; Virulence (Microbiology); Virulence - genetics; Yeast; United Kingdom; United Kingdom > UK
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0043559

Dihydroxyacid dehydratase (DHAD) is a key enzyme in the branched-chain amino acid biosynthetic pathway that exists in a variety of organisms, including fungi, plants and bacteria, but not humans. In this study we identified four putative DHAD genes from the filamentous fungus Aspergillus fumigatus by homology to Saccharomyces cerevisiae ILV3. Two of these genes, AFUA_2G14210 and AFUA_1G03550, initially designated AfIlv3A and AfIlv3B for this study, clustered in the same group as S. cerevisiae ILV3 following phylogenetic analysis. To investigate the functions of these genes, AfIlv3A and AfIlv3B were knocked out in A. fumigatus. Deletion of AfIlv3B gave no apparent phenotype whereas the Δilv3A strain required supplementation with isoleucine and valine for growth. Thus, AfIlv3A is required for branched-chain amino acid synthesis in A. fumigatus. A recombinant AfIlv3A protein derived from AFUA_2G14210 was shown to have DHAD activity in an in vitro assay, confirming that AfIlv3A is a DHAD. In addition we show that mutants lacking AfIlv3A and ilv3B exhibit reduced levels of virulence in murine infection models, emphasising the importance of branched-chain amino acid biosynthesis in fungal infections, and hence the potential of targeting this pathway with antifungal agents. Here we propose that AfIlv3A/AFUA_2G2410 be named ilvC.