Structural and functional features of the alpha-1 domain from human erythrocyte spectrin.

The complete sequence of the alpha-I domain of human erythrocyte spectrin has been determined. It contains a single type of internal homology comprised of multiple 106 amino acid repeats consistent with the occurrence of multiple gene duplications during the course of spectrin evolution. The only portion of the alpha-I sequence that does not appear to contain the sequence repeat is a segment containing the amino terminal 17 residues which may contain all or part of the alpha subunit portion of the self-association site. Secondary structural predictions and modeling suggest that each repeat unit contains a triple helical segment approximately 50 A in length. The alpha-I sequence is apparently unrelated to any other known protein sequence and apparently represents the first structural elucidation of a new class of proteins.