Figure 4.

Quantitative two-hybrid analysis. A. The Cdc1 mutants, arranged depending on the position of the mutation within the Cdc1 protein, from N- to C-terminus, were tested for their ability to interact with Cdc27 using the two-hybrid system in S.cerevisiae CTY10-5d. Quantitative values were obtained using an ONPG-based β-galactosidase assay from liquid cultures (see Methods). Values are expressed in arbitrary units with the wild-type Cdc1-Cdc27 interaction being set at 100 units (~65 Miller units of β-galactosidase activity, see [20]). B. Similar analysis of Cdc1-Pol3 interactions, performed in the presence of Cdc27 (see text).