Immunoreactive forms of human erythrocyte ankyrin are present in diverse cells and tissues

Abstract

Ankyrin is a polypeptide of molecular weight (MW) 200,000 which is tightly bound to the cytoplasmic surface of the human erythrocyte membrane and has been identified as the high-affinity membrane attachment protein for spectrin^1–3. This protein has also been shown to be associated with band 3 (ref. 4), the major transmembrane protein in erythrocytes. Ankyrin is thus an example of a polypeptide which links a cytoplasmic structural protein to an integral membrane protein. A water-soluble, 72,000-MW, proteolytic fragment of ankyrin has been purified which retains the ability to bind to spectrin, and competitively inhibits reassociation of spectrin with membranes⁵. Monospecific antibodies directed against this fragment have been prepared¹ and demonstrated to cross-react only with ankyrin among the erythrocyte membrane proteins^1,4. The present study reports the use of these antibodies to develop a radioimmunoassay capable of detecting femtomolar quantities of ankyrin, and demonstrates the presence of small but significant amounts of immunoreactivity in a variety of types of cells and tissues.