Developmental changes in membrane proteins from baboon erythrocytes

1. Total membrane proteins from freshly isolated erythrocytes of fetal, newborn, and adult baboons were analyzed by electrophoresis. 2. The electrophoretic patterns of proteins from newborns and adults were similar but those from adults and fetuses were different. 3. Four proteins, P165, P155, P75, and P49, with approximate mol. wts of 165,000, 155,000, 75,000, and 49,000, respectively, were present in adult but not in fetal samples. 4. P155 and P49, were glycoproteins; P49 was a cell-surface protein. 5. The membrane protein characteristics of the adult erythrocyte differ from those of the fetal erythrocytes and at least four polypeptides are associated with development of the adult phenotype.