Demonstration of immunoreactive forms of erythrocyte protein 4.2 in nonerythroid cells and tissues.

Protein 4.2 is a major component of the erythrocyte membrane cytoskeleton. Here we show that immunoreactive forms of human (Mr 72,000) and pig (Mr 75,000) protein 4.2 are also associated with the plasma membrane of various nonerythroid cells and tissues, such as platelets, brain, and kidney. Protein 4.2 can be extracted from platelet membranes under the same conditions (pH 11, 1 M KI, 1 M urea) which are required to extract protein 4.2 from the erythrocyte plasma membrane. The demonstration of protein 4.2 in nucleated cells that contain also several other proteins of the erythrocyte membrane cytoskeleton indicates some general principles underlying the molecular construction of the plasma membrane in erythrocytes and nonerythroid cells.