FIGURE 4: Gap1 interacts in vitro with the three catalytic subunits of PKA. The indicated GST-tagged proteins were purified from bacteria using glutathione-Sepharose beads and incubated with cell extracts from yeast cells expressing Gap1-HA. GST-pull down assay, followed by SDS-PAGE, Western blotting detection with peroxidase coupled anti-HA antibody demonstrates interaction between Gap1-HA and Tpk1-GST, Tpk2-GST and Tpk3-GST. No Gap1 was recovered using GST alone.