| First Author | Koizumi A | Year | 2011 |
| Journal | Proc Natl Acad Sci U S A | Volume | 108 |
| Issue | 40 | Pages | 16819-24 |
| PubMed ID | 21949380 | Mgi Jnum | J:177470 |
| Mgi Id | MGI:5295139 | Doi | 10.1073/pnas.1016644108 |
| Citation | Koizumi A, et al. (2011) Human sweet taste receptor mediates acid-induced sweetness of miraculin. Proc Natl Acad Sci U S A 108(40):16819-24 |
| abstractText | Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. |
