Asynchronous synthesis of erythrocyte membrane proteins.

The synthesis of membrane proteins of the mature mouse erythrocyte is asynchronous. During erythropoiesis, synthesis of the bulk of the spectrin and actin polypeptides is completed before that of the major transmembrane glycoprotein. Synthesis of the glycoprotein ceases before that of several minor proteins found on the inner surface of the red cell membrane, and one of these minor proteins is made predominantly by reticulocytes. These findings were the result of experiments in which a normal mouse was given a single injection of [35S]methionine. The appearance of radioactivity in the membrane proteins of circulating mature erythrocytes was followed. The earliest labeled proteins to emerge into the blood represent those synthesized at the last stages of erythropoiesis.