Yeast Y187 cells were cotransformed with expression vectors encoding various Gal4 DNA binding domain and Gal4 activation domain fusion proteins. Each transformation mixture was plated on synthetic dextrose plates lacking tryptophan and leucine. Interaction was measured by the liquid culture β-galactosidase assay as described (Fields and Song, 1989; Clonetech).

Values are representative of experiments repeated twice with similar results.