The use of one- and two-dimensional electrophoresis for investigating protein-protein interactions in erythrocyte plasma membranes

Membranes are the biological barriers which separate the cell contents from the environment. Communication across these barriers is mediated by proteins, many of which are assembled into oligomeric and multimeric complexes which catalyze movement of materials and information across the membrane. Until recently, native membrane proteins were not easily characterized except by laborious purification and reconstitution schemes. The findings described herein document the development and use of high resolution isoelectric focusing procedures as direct ways to probe the polypeptide composition of biological membranes, to determine the overall polypeptide composition of a membrane, to compare membranes from different cell populations, and to analyze associations among membrane proteins. A high resolution, denaturing isoelectric focusing procedure was developed which did not require SDS solubilization prior to focusing. Pigeon and human erythrocyte membranes were compared using the procedure. Conserved proteins included those of the membrane skeletal protein network, and anion transport protein. The pigeon membrane proteins were less glycosylated and the homologue of the major sialoglycoprotein, glycophorin, could not be definitely assigned. Associations among the proteins of the erythrocyte membrane and between the NADH and succinic dehydrogenases of the mitochondrial membranes were examined. Proteins associated with the erythrocyte membrane skeletal complex included the anion transport protein, ankyrin, glyceraldehyde-3-phosphate dehydrogenase and the acetylcholinesterase, although the latter association may have been nonspecific. Proteins which migrated independently of the membrane skeletal complex included the calcium ATPase, the glucose porter, glycophorin, hemoglobin and catalase