Fig. 5. Induction and phosphorylation of Sip4 protein requires specific β-subunits. Western blots of yeast cell extracts were analyzed for the accumulation and mobility of the Sip4-HA protein. The gel mobilities of the phosphorylated and unphosphorylated forms of Sip4-HA are indicated. (A) Extracts were prepared from wild-type (lanes 1 and 2) or sip1Δ sip2Δ gal83Δ cells (lanes 3 and 4) grown in glucose media (repressed; R) or after shifting to glycerol–ethanol media for 6 h (derepressed; D). (B) Cell extracts were prepared from derepressed cells of strains bearing the indicated gene deletions. Lane 1 shows a shorter exposure of lane 3.