Spectrin is the major constituent of the cytoskeletal network underlying the erythrocyte plasma membrane. It associates with band 4.1 and actin to form the cytoskeletal superstructure of the erythrocyte plasma membrane. Interacts with calmodulin in a calcium-dependent manner. Native spectrin molecule is a tetramer composed of two antiparallel heterodimers joined head to head so that each end of the native molecule includes the C-terminus of the alpha subunit and the N-terminus of the beta subunit. Belongs to the spectrin family. Contaminating sequence. Potential poly-A sequence.