Olfactory receptor specific for 2-phenylethylamine, a trace amine present at high concentration in the urine of carnivore species, playing a key role in fear and avoidance responses. 2-phenylethylamine acts as a kairomone in the chemical detection of carnivore odor and triggers fear in mice. This receptor is probably mediated by the G(s)-class of G-proteins which activate adenylate cyclase. Specifically expressed in neurons of the olfactory epithelium, to discrete glomeruli predominantly localized to a confined bulb region. Present in the dorsal area of the main olfactory epithelium. Mice lacking Taar4 show an absence of aversion to low concentrations of volatile amines and to the odor of predator urine. Belongs to the G-protein coupled receptor 1 family.