Figure 3.

β-Trcp WD40-repeat domain recognizes GSK-3β-phosphorylated β-catenin in vitro. In this GST-pull-down assay, purified GST or GST-β-catenin was examined for its ability to bind ³⁵S-labeled β-Trcp. GST-β-catenin on beads was either untreated or were treated with purified GSK-3β in the presence or absence of ATP before incubation with β-Trcp. Note that, in this experiment, GSK-3β and ATP were removed from phosphorylated GST-β-catenin by extensively washing the GST-β-catenin on beads after phosphorylation and before incubation with β-Trcp. Lanes 1–3 represent 50% of the input ³⁵S-labeled β-Trcp or β-Trcp mutants used in each GST-pull-down assay.