Document Detail


Human sweet taste receptor mediates acid-induced sweetness of miraculin.
MedLine Citation:
PMID:  21949380     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
Ayako Koizumi; Asami Tsuchiya; Ken-ichiro Nakajima; Keisuke Ito; Tohru Terada; Akiko Shimizu-Ibuka; Loïc Briand; Tomiko Asakura; Takumi Misaka; Keiko Abe
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-09-26
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  108     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-05     Completed Date:  2011-12-13     Revised Date:  2013-06-27    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  16819-24     Citation Subset:  IM    
Affiliation:
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cell Line
Fluorescence
Glycoproteins / chemistry,  metabolism*
Humans
Hydrogen-Ion Concentration
Mice
Models, Molecular*
Protein Conformation*
Receptors, G-Protein-Coupled / chemistry,  metabolism*
Taste Buds / metabolism*
Chemical
Reg. No./Substance:
0/Glycoproteins; 0/Receptors, G-Protein-Coupled; 0/miraculin protein, Synsepalum dulcificum; 0/taste receptors, type 1
Comments/Corrections

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