Molecular mechanisms of olfaction

The recent advances in molecular aspects of olfaction suggest strategies for resolving fundamental questions. Progress may come from analogies between the visual and olfactory systems. The existence of tissue-specific G proteins, the apparently similar cyclic nucleotide-gated ion channels, and the similarities between retinol binding protein and odorant binding protein (OBP) are examples of heuristic analogies. One reason for the failure of ligand binding studies to identify odorant receptors in the past may involve interference by the high odorant binding capacity of OBP. Removal of OBP from olfactory tissue may permit specific ligand binding to odorant receptors. Alternatively, techniques of molecular cloning may lead to the identification of cDNA molecules coding for odorant receptors. The ability to measure OBP and, in the future, to measure odorant receptors may facilitate studies of biochemical causes for the anosmias.