EF-hand-like motif found in the dystrophin/dystrobrevin/dystrotelin family
The dystrophin/dystrobrevin/dystrotelin family has been characterized by a compact cluster of domains comprising four EF-hand-like motifs and a ZZ-domain, followed by a looser region with two coiled-coils. Dystrophin is the founder member of this family. It is a sub-membrane cytoskeletal protein associated with the inner surface membrane. Dystrophin and its close paralog utrophin have a large N-terminal extension of actin-binding CH domains, up to 24 spectrin repeats, and a WW domain. Its further paralog, dystrophin-related protein 2 (DRP-2), retains only two of the spectrin repeats. Dystrophin, utrophin or DRP2 can form the core of a membrane-bound complex consisting of dystroglycan, sarcoglycans and syntrophins, known as the dystrophin-glycoprotein complex (DGC) that plays an important role in brain development and disease, as well as in the prevention of muscle damage. Dystrobrevins, including alpha- and beta-dystrobrevin, lack the large N-terminal extension found in dystrophin, but alpha-dystrobrevin has a characteristic C-terminal extension. Dystrobrevins are part of the DGC. They physically associate with members of the dystrophin family and with the syntrophins through their homologous C-terminal coiled coil motifs. In contrast, dystrotelins lack both the large N-terminal extension found in dystrophin and the obvious syntrophin-binding sites (SBSs). Dystrotelins are not critical for mammalian development. They may be involved in other forms of cytokinesis. Moreover, dystrotelin is unable to heterodimerize with members of the dystrophin or dystrobrevin families, or to homodimerize.