Structural highlights
FunctionGUR_GYMSY Suppresses strongly the sweet taste responses in the rat with high specificity to sucrose, glucose, glycine, and saccharin. This effect is reversible, but complete recovery of the suppressed responses required at least 3h. Gurmarin showed no effect or only a very weak effect on the sweet taste sensation in humans. Publication Abstract from PubMedGurmarin 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 A 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. The Crystal Structure of Gurmarin, a Sweet Taste-Suppressing Protein: Identification of the Amino Acid Residues Essential for Inhibition.,Sigoillot M, Brockhoff A, Neiers F, Poirier N, Belloir C, Legrand P, Charron C, Roblin P, Meyerhof W, Briand L Chem Senses. 2018 Sep 22;43(8):635-643. doi: 10.1093/chemse/bjy054. PMID:30137256[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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