DISTRIBUTIONS OF PROTEINS AND LIPIDS IN THE ERYTHROCYTE-MEMBRANE

Fluorescence digital imaging microscopy was used to characterize eryth rocyte membrane domains. To investigate the role of specific proteins in forming lipid domains, erythrocyte ghosts were double-labeled with fluorescent phospholipids and a fluorescent label specific for band 3, the major integral membrane protein. Areas of enrichment, or domains, were observed for both the protein and lipid components. The size and enrichment of the protein and lipid domains in the membrane depended upon the ionic strength but not the temperature. Also, there was a hig her correlation between the areas of band 3 and phosphatidylcholine en richment than between band 3 and phosphatidylserine enrichment. This i s consistent with band 3 playing a role in the formation of the phosph atidylcholine domains. Furthermore, areas of spectrin enrichment also were observed in immunofluorescently labeled ghosts, and the band 3 do mains were found to coincide with the spectrin domains. Thus, the dist ribution of band 3 in ghosts is influenced by interactions with the cy toskeleton. Together, these experiments illustrate the type of membran e heterogeneity present in erythrocyte ghosts and the type of lipid an d protein interactions that can affect the domains.