Fig. 5. Subcellular fractionation of K562 cells. K562 cells were broken by nitrogen cavitation and the resulting lysate was clarified by centrifugation. The postnuclear supernatant was layered over the top of a sucrose density gradient and centrifuged (30,000 rpm, 2 hours). The four fractions and the pellet (fraction 5) were collected from the top of the tube and characterized by western blot using antibodies directed against TfR2, TfR1, Rab5, Rab11, Lamp-2 and Golgin-97.