Schematic structure of Pls1 tetraspanins. Tetraspanins contain four transmembrane domains (TM1 to TM4) with conserved polar/charged residues (pink circles), a small extracellular loop (ECL1), a small intracellular loop (ICL) and a large extracellular loop (ECL2). ECL2 contains a CCG motif and further two conserved cysteine residues (yellow circles). The N-terminal and C-terminal tails are intracellular. These cysteine residues allow formation of two disulphide bridges (red lines), crucial for the folding of ECL2. One putative palmitoylation site is located proximal to TM4 (green circle).