Snf3 is a plasma membrane protein in yeasts that consists of 12 (2x6) transmembrane domains, like the homologous glucose transporters. Its structure is distinct from the homologous transporters in particular by a long C-terminal tail which is predicted to reside in the cytoplasm.
The long C-terminal tail plays an important role in glucose signaling and is probably the signaling domain itself. A soluble version of the C-terminal tail alone is sufficient to induce glucose transport.
All glucose transporters including Snf3 contain an arginine residue situated in a cytoplasmic loop preceding the fifth transmembrane domain. If this position is mutated, Snf3 adopts a state of constant glucose induction irrespective of whether there are nutrients present or not; this suggests an involvement in the glucose sensing process.