Typical Umami Ligand-Induced Binding Interaction and Conformational Change of T1R1-VFT

Umami taste receptor type 1 member 1/3 (T1R1/T1R3) heterodimer has multiple ligand-binding sites, most of which are located in T1R1-Venus flytrap domain (T1R1-VFT). However, the critical binding process of T1R1-VFT/umami ligands remains largely unknown. Herein, T1R1-VFT was prepared with a sufficient amount and functional activity, and its binding characteristics with typical umami molecules (monosodium l-glutamate, disodium succinate, beefy meaty peptide, and inosine-5'-monophosphate) were explored via multispectroscopic techniques and molecular dynamics simulation. The results showed that, driven mainly by hydrogen bond, van der Waals forces, and electrostatic interactions, T1R1-VFT bound to umami compound at 1:1 (stoichiometric interaction) and formed T1R1-VFT/ligand complex (static fluorescence quenching) with a weak binding affinity (K-a values: 252 +/- 19 to 1169 +/- 112 M-1). The binding process was spontaneous and exothermic (Delta G, -17.72 to -14.26 kJ mol(-1); Delta H, -23.86 to -12.11 kJ mol(-1)) and induced conformational changes of T1R1-VFT, which was mainly reflected in slight unfolding of alpha-helix (Delta alpha-helix < 0) and polypeptide chain backbone structure. Meanwhile, the binding of the four ligands stabilized the active conformation of the T1R1-VFT pocket. This work provides insight into the binding interaction between T1R1-VFT/umami ligands and improves understanding of how umami receptor recognizes specific ligand molecules.

Automated summary

In this study, the binding characteristics between T1R1-VFT and umami molecules were explored through experiments and simulations. The results showed that the binding process is driven by hydrogen bond, van der Waals forces, and electrostatic interactions, and induces conformational changes of T1R1-VFT. These findings improve our understanding of how the umami receptor recognizes specific ligand molecules.