G protein-coupled receptor 55 (GPR55) was first cloned in 1999 and is a 319 amino acid seven transmembrane G protein-coupled receptor (GPCR) that is mapped to chromosome 2q37 (human) (Sawzdargo et al. 1999). It displays features common with other Family A GPCRs including a short extracellular N-terminal and C-terminal tail and contains two highly conserved extracellular cysteine residues that form disulfide bonds to help stabilize the receptor structure. Glycosylation sites in its N-terminus are present, while its intracellular loops and C-terminal tail have a number of potential phosphorylation sites.