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The Crystal Structure of Gurmarin, a Sweet Taste-Suppressing Protein: Identification of the Amino Acid Residues Essential for Inhibition.

par Sigoillot, Maud ;Brockhoff, Anne;Neiers, Fabrice;Poirier, Nicolas;Belloir, Christine;Legrand, Pierre;Charron, Christophe;Roblin, Pierre;Meyerhof, Wolfgang;Briand, Loïc
Référence Chemical senses, 43, 8, page (635-643)
Publication Publié, 2018-09

Article révisé par les pairs

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Résumé :

Gurmarin is a highly specific sweet taste-suppressing protein in rodents that is isolated from the Indian plant Gymnema sylvestre. Gurmarin consists of 35 amino acid residues containing 3 intramolecular disulfide bridges that form a cystine knot. Here, we report the crystal structure of gurmarin at a 1.45 Å resolution and compare it with previously reported nuclear magnetic resonance solution structures. The atomic structure at this resolution allowed us to identify a very flexible region consisting of hydrophobic residues. Some of these amino acid residues had been identified as a putative binding site for the rat sweet taste receptor in a previous study. By combining alanine-scanning mutagenesis of the gurmarin molecule and a functional cell-based receptor assay, we confirmed that some single point mutations in these positions drastically affect sweet taste receptor inhibition by gurmarin.