Tetraspanins (aka TSPs) are eukaryotic membrane proteins involved in proliferation, adhesion, migration, fusion and signal transduction.

Tetraspanin proteins contain: four transmembrane domains; a short extracellular loop (EC1); a longer extracellular loop (EC2) and short N-terminal and C-terminal tails. Extracellular Domain 2 (EC2) contains: a constant region with three α-helices; and a variable region with sites for protein-protein interactions. Making a C-terminal deletion of the cytoplasmic tail produces a dominant-negative mutation. TSP6ΔCt was engineered lacking the 16 last C-terminal amino acids.