The tetraspanins are a superfamily of widely expressed membrane proteins with four conserved transmembrane domains, small (EC1) and large (EC2) extracellular domains, and short cytoplasmic N and C-termini. Tetraspanins have been linked to many basic cell processes including adhesion, motility, activation and fusion. However, the function of individual tetraspanins remains difficult to define. This project investigated the function of human tetraspanin CD63, by studying the behaviour of mutants transfected into model cell lines. CD63 is mainly associated with membranes of intracellular...