A Novel Multigene Family May Encode Odorant Receptors: A Molecular Basis for Odor Recognition

Linda Buck* and Richard Axel*l"
*Department of Biochemistry and Molecular Biophysics
l"Howard Hughes Medical Institute
College of Physicians and Surgeons
Columbia University
New York, New York 10032

Summary
The mammalian olfactory system can recognize and
discriminate a large number of different odorant molecules.
The detection of chemically distinct odorants
presumably results from the association of odorous
Ugands with specific receptors on olfactory sensory
neurons. To address the problem of olfactory perception
at a molecular level, we have cloned and characterized
18 different members of an extremely large
multigene family that encodes seven transmembrane
domain proteins whose expression is restricted to the
olfactory epithelium. The members of this novel gene
family are likely to encode a diverse family of odorant
receptors.

Introduction
In vertebrate sensory systems, peripheral neurons respond
to environmental stimuli and transmit these signals
to higher sensory centers in the brain where they are processed
to allow the discrimination of complex sensory information.
The delineation of the peripheral mechanisms
by which environmental stimuli are transduced into neural
information can provide insight into the logic underlying
sensory processing. Our understanding of color vision,
for example, emerged only after the observation that the
discrimination of hue results from the blending of information
from only three classes of photoreceptors (Rushton,
1955, 1965; Wald et al., 1955; Nathans et al., 1986). The
basic logic underlying olfactory sensory perception, however,
has remained elusive. Mammals possess an olfactory
system of enormous discriminatory power (for reviews
see Lancet, 1986; Reed, 1990). Humans, for example, are
thought to be capable of distinguishing among thousands
of distinct odors. The specificity of odor recognition is emphasized
by the observation that subtle alterations in the
molecular structure of an odorant can lead to profound
changes in perceived odor.