Fig. 1.

Interaction of Arl1 with the ArfGEF Gea2 and flippase Drs2 stimulates PS translocation at the TGN. Arl1 must be in its GTP-bound conformation to bind the N-terminal cytosolic tail of Drs2 and the N-terminal region of Gea2. These interactions stabilize Gea2 interaction with the C-terminal tail of Drs2 and stimulate flippase activity. PS is flipped to the cytosolic leaflet to generate an asymmetric membrane structure. Arl1–GTP and Drs2 flippase activity is required for recruitment of Imh1 via its GRIP domain. These events likely contribute to the budding of a vesicle that transports Gas1 to the plasma membrane.