Odorant-Receptor Interaction - Bioelectronic Nose: Integration of Biotechnology and Nanotechnology - page 68

Chapter 4
Odorant-Receptor Interaction

Xubo Su, Hiroaki Matsunami and Hanyi Zhuang

Abstract Odorant-receptor interactions constitute a key step in the olfactory detec-
tion of chemical compounds. Various studies support the combinatorial coding
of olfaction, in which each odorant activates an array of odorant receptors and
each odorant receptor is capable of recognizing multiple odorants, while large-
scale studies involving numerous odorants and odorant receptors help to resolve
the tuning specificities of receptor repertoires. In the meantime, the proteinaceous
content of the nasal mucus, including odorant binding proteins and different types
of xenobiotic-metabolizing enzymes, also contributes to odorant receptor activation
by transporting, concentrating, converting, and/or ultimately removing odorants
from nasal mucosa. In addition, the presence of metal ions, notably copper ions, is
known to be important for the activation of odorant receptors for certain types of
metal-coordinating odorants. Finally, prediction algorithms based on odorant prop-
erties and receptor structures are becoming increasingly feasible for investigating
detailed mechanisms involved in odorant-receptor interactions.

4.1 Introduction

The binding of an odorant to an odorant receptor (OR) is one of the crucial steps
from odorant inhalation to the eventual odor perception. Odorants are small, volatile
molecules of variable sizes, charges, and functional groups. The presence of tens
of thousands of odorant molecules in nature mandates that mammals be capable