DIFFUSIONAL MOBILITY OF GOLGI PROTEINS IN MEMBRANES OF LIVING CELLS

The mechanism by which Golgi membrane proteins are retained with in th e Golgi complex in the midst of a continuous flow of protein and lipid is not yet understood. The diffusional mobilities of mammalian Golgi membrane proteins fused with green fluorescent protein from Aequorea v ictoria were measured in living HeLa cells with the fluorescence photo bleaching recovery technique. The diffusion coefficients ranged from 3 x 10(-9) square centimeters per second to 5 x 10(-9) square centimete rs per second, with greater than 90 percent of the chimeric proteins m obile. Extensive lateral diffusion of the chimeric proteins occurred b etween Golgi stacks. Thus, the chimeras diffuse rapidly and freely in Golgi membranes, which suggests that Golgi targeting and retention of these molecules does not depend on protein immobilization.