1c4e
From Proteopedia
GURMARIN FROM GYMNEMA SYLVESTRE
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 35-residue polypeptide from the Asclepiad vine Gymnema sylvestre. It has been utilised as a pharmacological tool in the study of sweet-taste transduction because of its ability to selectively inhibit the neural response to sweet tastants in rats. We have chemically synthesised and folded gurmarin and determined its three-dimensional solution structure to high resolution using two-dimensional NMR spectroscopy. Structure calculations utilised 612 interproton-distance, 19 dihedral-angle, and 18 hydrogen-bond restraints. The structure is well defined for residues 3-34, with backbone and heavy atom rms differences of 0.27 +/- 0.09 A and 0.73 +/- 0.09 A, respectively. Gurmarin adopts a compact structure containing an antiparallel beta-hairpin (residues 22-34), several well-defined beta-turns, and a cystine-knot motif commonly observed in toxic and inhibitory polypeptides. Despite striking structural homology with delta-atracotoxin, a spider neurotoxin known to slow the inactivation of voltage-gated Na+ channels, we show that gurmarin has no effect on a variety of voltage-sensitive channels. High-resolution solution structure of gurmarin, a sweet-taste-suppressing plant polypeptide.,Fletcher JI, Dingley AJ, Smith R, Connor M, Christie MJ, King GF Eur J Biochem. 1999 Sep;264(2):525-33. PMID:10491100[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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