Domain structure of the plasma membrane : interaction between membrane skeleton and membrane receptors

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Movements of transferrin receptor molecules in the plasma membrane of cultured normal rat kidney fibroblastic cells were investigated by video-enhanced contrast optical microscopy with nanometer-level special precision and video-rate temporal resolution by lebeling the receptor with the ligand-coated 40-nm colloidal gold particles. Most of the movement trajectories are of the confined diffusion type within domains of -0.25mum^2. Movement within the domains is random with a diffusion coefficient -10^<-9> cm^2/s, which is consistent with that expected for free Brownian diffusion of proteins in the plasma membrane. The receptor molecules move from one domain to one of the adjacent domains at an average frequency of 0.034s^<-1>, indicating that the plasma membrane is compartmentalized for diffusion of membrane receptors and that long-range diffusion is the result of successive intercompartmental jumps. Partial destruction of the cytoskeleton suggest that the boundaries between compartments are made of dynamically fluctuating membrane skeletons.