Characterization of the Binding Site of Aspartame in the Human Sweet Taste Receptor

Chem Senses. 2015 Oct;40(8):577-86. doi: 10.1093/chemse/bjv045.

Abstract

The sweet taste receptor, a heterodimeric G protein-coupled receptor comprised of T1R2 and T1R3, binds sugars, small molecule sweeteners, and sweet proteins to multiple binding sites. The dipeptide sweetener, aspartame binds in the Venus Flytrap Module (VFTM) of T1R2. We developed homology models of the open and closed forms of human T1R2 and human T1R3 VFTMs and their dimers and then docked aspartame into the closed form of T1R2's VFTM. To test and refine the predictions of our model, we mutated various T1R2 VFTM residues, assayed activity of the mutants and identified 11 critical residues (S40, Y103, D142, S144, S165, S168, Y215, D278, E302, D307, and R383) in and proximal to the binding pocket of the sweet taste receptor that are important for ligand recognition and activity of aspartame. Furthermore, we propose that binding is dependent on 2 water molecules situated in the ligand pocket that bridge 2 carbonyl groups of aspartame to residues D142 and L279. These results shed light on the activation mechanism and how signal transmission arising from the extracellular domain of the T1R2 monomer of the sweet receptor leads to the perception of sweet taste.

Keywords: aspartame; cyclamate; homology modeling; site-directed mutagenesis; sweet taste receptor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aspartame / chemistry
  • Aspartame / metabolism*
  • Binding Sites
  • Dimerization
  • HEK293 Cells
  • Humans
  • Hydrogen Bonding
  • Hydrophobic and Hydrophilic Interactions
  • Mice
  • Molecular Docking Simulation
  • Mutagenesis, Site-Directed
  • Protein Binding
  • Protein Structure, Quaternary
  • Receptors, G-Protein-Coupled / chemistry
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Sweetening Agents / chemistry
  • Sweetening Agents / metabolism*
  • Taste / physiology

Substances

  • Receptors, G-Protein-Coupled
  • Sweetening Agents
  • taste receptors, type 1
  • Aspartame