Odorant-binding protein (OBP) is found in nasal epithelium, and it selectively binds odorants. Three complementary DNAs encoding rat odorant-binding protein have now been cloned and sequenced. One clone contains an open reading frame predicted to encode an 18,091-dalton protein. RNA blot analysis confirms the localization of OBP messenger RNA in the nasal epithelium. This OBP has 33 percent amino acid identity to α2- microglobulin, a secreted plasma protein. Other members of an α2-microglobulin super-family bind and transport hydrophobic ligands. Thus, OBP probably binds and carries odorants within the nasal epithelium to putative olfactory receptors.
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