Figure 1.

An overview of the yeast display system used in the evolution of bond-forming enzymes. The enzyme library is displayed on the yeast surface fused to the Aga2p mating factor. Aga2p is bound covalently to the Aga1p mating factor. Substrate 1 is linked to the system via the reactive handle S6. Substrate 2, which is conjugated to an affinity tag, is added to the system. Only active library members will catalyze the reaction between substrate 1 and 2. This is followed by the addition of a fluorescent molecule that binds to the affinity handle and screening using FACS [20].