TRIM 9, also referred to as Spring, is a member of the tripartite motif protein family. These proteins are composed of three zinc-binding domains, a RING, a B-box type 1, a B-box type 2 and a coiled-coil region. Proteins belonging to this large family are involved in cellular processes ranging from cell-growth and development to the regulation of fusion events necessary for exocytosis.
TRIM 9 is expressed selectively in the adult and embryonic nervous system and has been implicated in the regulation of synaptic vesicle exocytosis via SNAP 25 interaction. Several splice variant with molecular weights from 60 - 80 kDa have been described.