Olfactory marker protein (OMP) is an abundant, 19kD, cytosolic protein that is almost exclusively expressed in mature, functioning, olfactory neurons but not in the neural precursor basal cells. The OMP gene structure and protein sequence are highly conserved between mouse, rat and human. Its tissue-specific expression in the receptor cells together with the results of the mouse knockout studies show that OMP represents a novel modulatory component of the odor detection/signal transduction cascade. May act as a modulator of the olfactory signal-transduction cascade.