Olfactory receptors are G protein-coupled receptors that localize to the cilia of olfactory sensory neurons where they display affinity for and bind to a variety of odor molecules. The genes encoding olfactory receptors comprise the largest family in the human genome. The binding of olfactory receptor proteins to odor molecules triggers a signal transduction that propagates nerve impulses throughout the body, ultimately leading to transmission of the signal to the brain and the subsequent perception of smell. PSGR (prostate-specific G-protein coupled receptor), also known as OR51E2 (olfactory receptor 51E2), is a 320 amino acid multi-pass membrane protein that belongs to the olfactory receptor subfamily of G-protein coupled receptors. Expressed exclusively in prostate tissue and upregulated in prostate cancer, PSGR functions as an odorant receptor that binds odorant molecules and triggers the perception of smell.