The ERM family includes ezrin, radixin, moesin and merlin. They are composed of a N-terminal FERM (ERM) domain (also called N-ERMAD (N-terminal ERM association domain)), a coiled coil region (CRR), and a C-terminal domain CERMAD (C-terminal ERM association domain) which has an F-actin-binding site (ABD). Two actin-binding sites have been identified in the middle and N-terminal domains. Merlin is structurally similar to the ERM proteins, but instead of an actin-binding domain (ABD), it contains a C-terminal domain (CTD), just like the proteins from the 4.1 family. Activated ezrin, radixin and moesin are thought to be involved in the linking of actin filaments to CD43, CD44, ICAM1-3 cell adhesion molecules, various membrane channels and receptors, such as the Na+/H+ exchanger-3 (NHE3), cystic fibrosis transmembrane conductance regulator (CFTR), and the beta2-adrenergic receptor. The ERM proteins exist in two states, a dormant state in which the FERM domain binds to its own C-terminal tail and thereby precludes binding of some partner proteins, and an activated state, in which the FERM domain binds to one of many membrane binding proteins and the C-terminal tail binds to F-actin. The FERM domain has a cloverleaf tripart structure composed of: (1) FERM_N (A-lobe or F1); (2) FERM_M (B-lobe, or F2); and (3) FERM_C (C-lobe or F3). The C-lobe/F3 within the FERM domain of ERM is part of the PH domain family. The FERM domain is found in the cytoskeletal-associated proteins such as ezrin, moesin, radixin, 4.1R, and merlin. These proteins provide a link between the membrane and cytoskeleton and are involved in signal transduction pathways. The FERM domain is also found in protein tyrosine phosphatases (PTPs), the tyrosine kinases FAK and JAK, in addition to other proteins involved in signaling. This domain is structurally similar to the PH and PTB domains and consequently is capable of binding to both peptides and phospholipids at different sites.