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MAKING SENSE OF SWEETNESS Study explains a range of observations on effects of different sweeteners STU BORMAN Among the five senses, taste is probably the least understood. A new model of the human sweet-taste receptor now explains why diverse molecules, large and small, taste sweet and why sweet tastes are often additive. SWEET BONDAGE Model shows how the sweetener aspartame binds to a site on the sweetness receptor's T1R3 subunit. Red and blue are hydrogen-bond donor and acceptor residues, respectively; aspartame is in gold, except for its carboxylate (red) and ammonium (blue) groups. Model prepared with MOLMOL (J. Mol. Graphics 1996, 14, 51). ADAPTED FROM J. MED. CHEM. The model was created by chemistry professor Piero A. Temussi of the University of Naples and coworkers (J. Med. Chem. 2005, 48, 5520). If confirmed, it could aid the rational design of new sweeteners and lead to better treatments for diseases linked to sugar consumption (such as diabetes and obesity). For decades, most researchers believed there had to be multiple receptors for sweet taste, comments professor of biochemistry and molecular biology D. Eric Walters of Rosalind Franklin University of Medicine & Science, North Chicago, a specialist in computer modeling and sweet-taste transduction. "Sugars, amino acids, peptides, proteins, terpenes, heterocycles like saccharin, sulfamic acids, ureas, guanidines, and dozens of other classes of compounds taste sweet, and it was hard to envision any single binding site that could interact with all of them." The new study "suggests a way in which these results can be rationalized--[through] different binding sites on the receptor," Walters says. "The model is sufficiently detailed that you can now devise experiments to test the proposed sites. You can do specific mutations of residues implicated by the model and see whether receptor binding is affected." |
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