Atypical FERM-like domain C-lobe of Sorting nexin family
Sorting nexins function in regulating recycling from endosomes to the cell surface. SNX17, SNX27, and SNX31 contain a N-terminal PX domain, a FERM-like domain, and a unique C-terminal region. All three proteins are able to bind the Ras GTPase through their FERM-like domains. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. These interactions place the PX-FERM-like proteins at a hub of endosomal sorting and signaling processes. These proteins participate in a network of interactions that will impact on both endosomal protein trafficking and compartment specific Ras signaling cascades. The typical 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 is part of the PH domain family. FERM domains are found in 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.