Fig. 6. Tyrosine phosphorylation of Cdc28 is Swe1 but not Slt2-dependent. Cultures of the indicated genotype were grown to mid-log phase and treated with 0.5% IAA. At the indicated times, total protein extracts were obtained by TCA precipitation and probed by western blotting with anti-phosphotyro-Cdc28 (anti-pY19) and anti-active Slt2 antisera. The membrane was then stripped and probed with anti-PSTAIR antisera. Levels of activated Slt2 and phosphotyro-Cdc28 were determined using the signal from the lower band (Cdc28) in the anti-PSTAIR panel as a loading control. Values on the ordinate are the ratio of each experimental signal to its loading control.