Figure 1.

Biochemical and genetic complementation of the acid phosphatase regulation defect in a pho85Δ mutant by Cdk5 expression. (A) Complementation of defect in acid phosphatase regulation. Acid phosphatase activity was measured in pho85Δ strains containing pCDK5 or pCDK5-I and a PHO80 expression plasmid (pPho80) or a control vector (p230v). Acid phosphatase activity from a wild-type strain is also shown (wt). These strains were grown in repressed (7.4 mM phosphate, shaded bars) and derepressed (3.7 μM phosphate, solid bars) conditions. Values are normalized for cell density (OD₆₀₀). (B) Pho4 kinase assays with HA-Pho80-Cdk5. HA-Pho80 was immunoprecipitated from yeast extracts and used in kinase assays with Pho4 as substrate. The following strains were used for extract preparation: lane 1, pho85Δ transformed with pCDK5 and pHA-Pho80; lane 2, pho85Δ strain with pCDK5-I and pPho80; lane 3, pho85Δ strain with pCDK5 and pBA230v; lane 4, wild-type strain with pHA-Pho80 (positive control).