Protein sequencing domain duplication

The sequencing of a- and /3-spectrin, a-actinin, and dystrophin has revealed similarities not only within the spectrin repeat, but also the other domains and motifs present within these proteins. Subsequent analyses have revealed an evolutionary pathway for the divergence of spectrin and dystrophin from a common a-actinin ancestor via a series of rearrangements, duplications, and evolution of repeats and other domains, as well as the acquisition of unique domains such as PH, WW, and SHS (Fig. 2). 

---