Aureobasidin A (AbA) is a cyclic depsipeptide antibiotic, isolated from the filamentous fungus Aureobasidium pullulans R106, which is toxic to yeast at low concentrations (0.1–0.5 µg/ml). Sensitive species include Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida glabrata, Aspergillus nidulans, and A. niger.

AbA inhibits a yeast enzyme, inositol phosphorylceramide (IPC) synthase, which is expressed from the AUR1 gene (Takesako et al. 1993, Hashida-Okado et al. 1996). Expression of a mutant gene, AUR1-C, in transformed yeast confers resistance to the drug. It is this gene that is used in Matchmaker Gold systems as a reporter for protein interactions.

Perfect reporter for yeast two-hybrid studies

AbA selection virtually eliminates the high numbers of background colonies that often plague low-stringency primary screens that use nutritional markers alone (e.g. HIS3). Because AbA actually kills sensitive yeast cells, rather than merely retarding their growth, AbA-based selection greatly favors the growth and identification of genuinely positive clones. In general practice, a high percentage of clones that emerge from low-stringency primary screens using AbA selection alone, are subsequently verified on high-stringency secondary screens that select for all four Matchmaker Gold reporters (AUR1-C, HIS3, ADE2 and MEL1).