Two T1R3 proteins join to form a sweet-taste receptor. The red 'glob' (white arrow) is a bulky sugar molecule that modifies the sweet-taste receptor in the non-taster mice. The researchers believe that structural alterations caused by the addition of the sugar molecule prevent the receptor from functioning properly. This could make the non-taster mice less responsive to sweet foods.
Courtesy Robert Margolskee and Gopi Shanker