Figure 3.

GAIP behaves as an integral membrane protein. Membrane fractions (100,000 × g pellet) from AtT-20 cells stably expressing GAIP (clone 14) were treated with Na₂CO₃. Proteins were separated by SDS/12% PAGE and immunoblotted. (A) GAIP remains associated with the membrane fraction (P) after Na₂CO₃ treatment and is not detected in the soluble fraction (S). (B) Cab45, a soluble luminal Golgi protein, is released from the membrane fraction (P) and appears in the supernatant (S) after Na₂CO₃ treatment.