Fig. 3. COPI-coated vesicles from ypt1/SLY1-20 Golgi are depleted from cargo and SNAREs. Golgi membranes enriched from either wild-type (A) or ypt1/SLY1-20 (B) cells were incubated with Arf1p, coatomer and GTP--S, to generate COPI vesicles. The vesicles were separated by velocity sedimentation centrifugation. The vesicle peak was collected and floated on a buoyant density gradient. Fractions were collected from the top, precipitated, and analyzed by immunoblotting. Sec22p is a v-SNARE in the ER-Golgi shuttle and Emp47p is a vesicle cargo. The arrows indicate the movement of the lipid particles in the gradient.