Plasma membrane, sweet taste receptor

It has been proposed " that the mechanism(s) of action of gymnemic acids and ziziphins is a biphasic, model-membrane penetration-process. The model suggested that the modifier molecules interact first with the receptor-cell plasma-membrane surface. It was postulated that this initial interaction involves a selective effect on taste perception, including the transduction and quality specification of the sweet stimuli, and selective depression of sweetness perception. Following the initial interaction, the modifier molecules interact with the membrane-lipid interior to produce a general disruption of membrane function and a nonselective effect on taste... 

Additional evidence that the exterior surface of the taste receptor cell plasma membrane is the location of the sweet receptor is provided by the action of the chemostimulatory proteins, monellin and thaumatin. Monellin occurs in the fruit of the African serendipity berry (Dioscoreophyllum cumminsii), and thaumatin is found in the fruit of Thaumatococcus daniellii, also... 

The effects of miraculin, monellin and thaumatin, taken together, provide evidence that the sweetness receptor site is located at the surface of the taste receptor cell, in or in close proximity to, the plasma membrane. 

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