non-canonical GAT domain found in metazoan signal transducing adapter molecules (STAMs) and similar proteins
STAMs are Hrs-binding proteins involved in intracellular signal transduction mediated by cytokines and growth factors. They are components of the ESCRT-0 complex that binds ubiquitin and acts as sorting machinery that recognizes ubiquitinated receptors and transfers them for further sequential lysosomal sorting/trafficking processes. Members of this family contain a non-canonical GAT (GGA and Tom1) domain consisting of two helices. A canonical GAT domain is a monomeric three-helix bundle that bind to ubiquitin. STAM, together with another GAT domain-containing protein Hrs, forms a Hrs/STAM core complex that consists of two intertwined GAT domains, each consisting of two helices from one subunit, and one from the other subunit. The two GAT domains are connected by a two-stranded coiled-coil. The Hrs/STAM complex, an intertwined GAT heterodimer, is a scaffold for binding of ubiquitinated cargo proteins and coordinating ubiquitination and deubiquitination reactions that regulate sorting.