Fig. 4. Sucrose flotation gradients in the presence of Triton X-100. COS-7 cells transfected with the GFP-tagged constructs were extracted in the presence of Triton X-100 at 4°C and subjected to centrifugation on a 40:30:5% sucrose gradient as described in the Materials and Methods. After centrifugation, the gradient tubes were divided into 12 equal aliquots collected from the bottom and analyzed by SDS-PAGE and western blotting. The amount of protein in each sample was determined using a micro-Lowry method (upper panel; average distribution). Similar results were obtained in four independent experiments.