FIG. 3.

Specific hydrophobic amino acids are essential for transcriptional activation by the Hap4 aa 124 to 329 fragment. The amino acid sequence of Hap4(124-160) is shown in single-letter code; underlined positions show sites of serine substitutions. LexA-Hap4(124-329) fusion proteins, with or without the indicated substitutions, were expressed in yeast strain L40 and assayed for activation of the integrated lacZ reporter gene as described for Fig. 2. The histograms indicate means (with standard deviations) of β-galactosidase activity in yeast cell extracts from three parallel cultures.