The α- and β-subunits of spectrin are made of repeated homologous units of 106 residues. In the recently reported partial sequence of the chicken non-muscle α-actinin, a repetitive sequence homologous to the internal repeat in spectrin occurs several times. Both spectrin and α-actinin are components of the cytoskeletal network, the integrity of which is based on multiple and complex interactions. We suggest that the shared domain structure indicates common structural principles or interactions of spectrin and α-actinin and reflects their common evolution.
