Aureobasidin A (AbA) is a potent and unique yeast antibiotic that kills S. cerevisiae at low concentrations (Takesako et. al. 1993). The drug is a cyclic multipeptide (Figure 1) that acts by inhibiting inositol phosphorylceramide synthase, an essential yeast enzyme. A mutant enzyme, encoded by the AUR1-C gene, confers resistance to AbA and can be used as a highly effective selectable marker that requires little to no optimization. Our optimized Matchmaker Gold Yeast Two-Hybrid System leverages this by including a reporter strain containing a stably-integrated AUR1-C gene, allowing for simple and rapid colony screening in yeast two-hybrid (Y2H) libraries using AbA selection.
Low background with AbA screening
AbA selection virtually eliminates the high number of background colonies that often plague low-stringency primary screens that rely on nutritional markers alone (e.g., HIS3). Because AbA actually kills sensitive cells, rather than merely retarding their growth, AbA-based selection greatly favors the growth and identification of true positive clones. In general practice, a high percentage of clones that emerge from low-stringency primary screens using AbA selection are subsequently verified on high-stringency secondary screens that select for all four Matchmaker Gold reporters (AUR1-C, HIS3, ADE2, and MEL1).
AbA: ampicillin for yeast
Many researchers have yearned for a yeast selection system similar to those used for E. coli or mammalian cells. In fact, AbA is used for yeast in a similar way as ampicillin and kanamycin are used for cloning in E. coli, or as G418 is used for selection of stably-transfected mammalian cell clones. AbA resistance is far easier to use in Y2H library screening than auxotrophic reporters, which often require additional optimization steps to achieve selective growth conditions.