New insights into the characteristics of sweet and bitter taste receptors.

Understanding the molecular bases of taste is of primary importance for the field of human senses as well as for translational medical science. This chapter describes the complexity of the mechanism of action of sweet, bitter, and umami receptors. Most molecular weight sweeteners interact with orthosteric sites of the sweet receptor. The mechanism of action of sweet proteins is more difficult to interpret. In the only general mechanism proposed for the action of sweet proteins, the "wedge model," it is hypothesized that proteins bind to an external active site of the active conformation of the sweet receptor. This model can be updated by building topologically correct complexes of proteins with the receptor. Among the recent advances that will be described here are the discovery of taste modulators and the possibility that certain bitter compounds are recognized by the umami receptor.