Olfactory marker protein, also known as OMP, is uniquely associated with the mature olfactory receptor neurons in many vertebrate species from fish to man. It is expressed in the cytoplasm of olfactory chemosensory neurons in the nasal neuroepithelium. OMP expression is a sign of mature vertebrate olfactory receptor neurons (ORNs). OMP may have a modulatory role in the odor detection/signal transduction cascade. In fetal olfactory epithelial cells, OMP is also a potent enhancer of mitosis, and it promotes an increase in uptake of tritiated thymidine in liver. Recombinant human OMP protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.