- Investigating Deliciousness: The Structure-Function Relationships of the Umami Taste Receptor
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Abstract:
- Umami, the essence of deliciousness, is classified as one of the five basic tastes after its identification in Japan in 1908. It is naturally present in foods such as cheese, tomatoes and seaweed. Flavours are detected along the gastrointestinal tract by taste receptors in cells ranging from the tongue papillae to those in the nasal cavity and at the top of the oesophagus. Umami flavour perception is realised in the brain after a signalling cascade within the cell is initiated by G-protein activation by an umami receptor. This investigation aims to determine the precise mechanism by which an umami ligand binds to the receptor, to ultimately enable flavour perception. In silico analysis through homology modelling, protein sequence alignments and simulations enabled prediction of the key binding site residues: T149, S172, Y220 and E301. Sequential binding analysis determined the glutamate ligand likely binds first to residue T149 in the large domain, lowering the entropic barrier and triggering closure of the ligand binding domain by the small domain. This movement secures the ligand in place through further interactions with S172, Y220 and E301. These interactions are hydrogen bonds and weak intermolecular forces, strong enough to hold the domain in the closed conformation but sufficiently weak to release the ligand after signal transduction. This investigation provides a strong foundation from which further research could be conducted. Mutagenesis studies could affirm, or adapt, these conclusions. Greater knowledge of the mechanism of activation of the umami receptor could benefit the food industry and enable production of more appetising products.
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