Molecular mechanisms of the action of miraculin, a taste-modifying protein.
ABSTRACT Miraculin (MCL) is a homodimeric protein isolated from the fruits of Richadella dulcifica, a shrub native to West Africa. Although it is flat in taste at neutral pH, MCL has taste-modifying activity in which sour stimuli produce a sweet perception. Once MCL enters the mouth, strong sweetness can be detected for more than 1h each time we taste a sour solution. While the human sweet taste receptor (hT1R2-hT1R3) has been identified, the molecular mechanisms underlying the taste-modifying activity of MCL remain unclear. Recently, experimental evidence has been published demonstrating the successful quantitative evaluation of the acid-induced sweetness of MCL using a cell-based assay system. The results strongly suggested that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH. Since sweet-tasting proteins may be used as low-calorie sweeteners because they contain almost no calories, it is expected that MCL will be used in the near future as a new low-calorie sweetener or to modify the taste of sour fruits.
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ABSTRACT: Grapevine is a large source of healthy polyphenols for human diet, and red table-grapes and wines are the main source of stilbenes. These compounds are important both in the plant defence system and for human health. In the present study, Vitis vinifera cv. Barbera cell cultures were treated with 50 μg/mL chitosan and proteomic analyses on soluble and membrane subcellular fractions were performed against suitable controls. Three soluble stilbene synthase (STS) protein spots, four STS spots in the microsomal fraction and four spots of membrane ATPase subunits were identified, the accumulation of which was modulated in response to chitosan treatment. Present proteomic and immunolocalisation data seem to provide evidence supporting the hypothesis that a stilbene biosynthetic multi-enzyme complex is associated with the intracellular membrane. In addition proteomic analyses showed a general decrease in the accumulation of proteins belonging to different primary metabolism pathways, both in the soluble and membrane fractions. In particular, energy, sugar and amino acid metabolisms were down regulated as a consequence of chitosan and acetic acid treatments. These metabolic modifications could lead to a consistent change in the profile and amount of metabolites stored in grape berries, with consequent effects on taste, flavour, organoleptic and nutraceutical properties of derived food products. This article is protected by copyright. All rights reserved.Electrophoresis 03/2014; · 3.16 Impact Factor