Unravelling the interaction between α-cyclodextrin with the thaumatin protein and a peptide mimic

Abstract

<div><p>G-protein-coupled receptors (GPCRs) are responsible for signal transduction; through these transmembrane proteins, our senses are evoked: sight, smell and taste. Thaumatin is a natural sweet-tasting protein that is 100,000 times sweeter than sucrose but its use in food products has been hampered due to a liquorice aftertaste. Thaumatin has been shown to bind to a class C GPCR and the active binding site of the thaumatin protein is known. Here, we report on the binding of a well-known food grade host: α-cyclodextrin to thaumatin. We show through a combination of one- and two-dimensional NMR experiments that α-cyclodextrin binds to aromatic residues on thaumatin with <i>K</i>_a = 8.5 ± 2.4 M^− 1. We also synthesise a heptapeptide KTGDRGF that mimics the active binding site of thaumatin and show that α-cyclodextrin binds to the C-terminal solvent accessible phenylalanine residue of this peptide with <i>K</i>_a = 8.8 ± 3.1 M^− 1. This indicates that α-cyclodextrin may interact with the active binding site on thaumatin, suggesting that α-cyclodextrin could be used to modify the interaction of thaumatin with GPCRs and hence its sweet-taste profile.</p></div