Figure 4.

Enhancement of AKIN kinase activation by the prl1 mutation and sucrose. (A) Protein extracts were prepared from shoots and roots of wild-type (wt) and prl1 mutant (prl) seedlings grown in the presence of either 0.1% (−) or 3% sucrose (+) in the light. The amount of kinase catalytic subunits was adjusted to equal in the samples by Western blot titration with the anti-NPK5 IgG followed by enhanced chemiluminescence detection. (B and C) Titration of kinase assay with AKIN immunocomplexes. Protein extract (75, 125, and 175 μg) from shoots (in B) and roots (in C) of wild-type (solid bars) and prl1 mutant (open bars) seedlings treated with 0.1 or 3% sucrose were immunoprecipitated with 10 μg anti-NPK5 IgG, bound to protein A-Sepharose, and used in kinase assays to measure AKIN activities. Units show pmol phosphate incorporation × 10⁻⁶ per pmol TRX-KD substrate per min.