Recent Advances in Structure and Function Studies on Human Bitter Taste Receptors

Humans are capable of sensing five basic tastes and of these, bitter taste sensation alone, is mediated by a large group of 25 cell surface proteins known as, bitter taste receptors (T2Rs). T2Rs belong to the G-protein coupled receptor (GPCR) superfamily. However, they share little homology with the large subfamily of Class A GPCRs. Very little progress has been made in understanding the dynamics of T2R activation, and in discovery of molecules that can block (bitter blockers) T2R activation. Only recently few structure-function studies focused on elucidating the ligand binding mechanisms of T2Rs have been published. Here we will discuss the roles of conserved amino acids in T2R structure-function, possible mechanisms of activation of T2Rs, and compare and contrast with the recent crystal structures of the Class A GPCRs.