Synaptotagmin-17 (SYT17) belongs to the synaptotagmin family, which is a group of membrane-trafficking proteins that contain two C-terminal C2 domains. Although synaptotagmins have been found to have a unique N-terminal domain that is involved in membrane anchoring (e.g., synaptotagmin) or specific ligand binding (e.g., rabphilin-3A and Doc2, ), SYT17 does not contain this domain. SYT17 is highly expressed in brain and kidney (B/K) []. However, despite the lack of a transmembrane domain, it is tightly bound to the membrane fraction after treatment with high concentration of salt or high pH. Deletion and mutation analyses indicate that the cysteine cluster at the N terminus is essential for membrane localisation of SYT17. When wild-type SYT17 is expressed in PC12 cells, SYT17 proteins are localised mainly to the perinuclear region (trans-Golgi network), whereas mutant SYT17 carrying Cys-to-Ala substitutions are cytosolic [].
