Fig. 1. Structural domains of selected members of the Protein 4.1 superfamily. The defining characteristic of all members is the highly homologous N-terminal FERM domain. The degree of similarity of FERM domains compared with that of the founding member of this superfamily, Protein 4.1R, are as follows: Protein 4.1N, 71%; Protein 4.1G, 74%; Protein 4.1B, 73%; ezrin/moesin/radixin, 24-32%; merlin, 28%; talin, 20%; PTPH, 37%; and NBL4, 40%. Merlin is structurally similar to the ERM proteins and these four proteins comprise the ERM subfamily. Domains shown in the prototypical Protein 4.1 are conserved among all members in the Protein 4.1 subfamily. Talin, PTPH, and NBL4 proteins are shown for comparison. ABD, actin-binding domain; CCR, predicted coiled-coil region; CTD, carboxyl terminal domain; FERM, Protein 4.1-ezrin-radixin-moesin domain; PTP, protein tyrosine phosphatase; SABD, spectrin-actin binding domain; U1, 2, 3, unique regions.

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