Syndeins: the spectrin-binding protein(s) of the human erythrocyte membrane.

Two-dimensional tryptic and chymotryptic analyses of all the major bands in a sodium dodecyl sulfate/polyacrylamide gel of the human erythrocyte membrane show that each band has a characteristic map. However, band 2.1 (nomenclature of T. L. Steck) and several polypeptides below this band exhibit similar tryptic and chymotryptic peptide maps and thus appear to be a family of closely related proteins or degradation products. Furthermore, they all contain a subset of peptides that are accounted for by the peptides from two known spectrin-binding fragments. We show that both fragments derive from 2.1-related proteins and conclude that band 2.1 and its related proteins, which we name "syndeins", bind spectrin and connect it to the erythrocyte membrane.