The taste-specific G-protein alpha-subunit, alpha-gustducin, was expressed using a baculovirus based system. alpha-Gustducin was demonstrated to be myristoylated and was also palmitoylated in insect larval cells. Recombinant alpha-gustducin was purified to homogeneity. Neither receptors nor effectors that interact with gustducin in taste are known. However, alpha-gustducin has a close structural similarity to the visual G-protein, alpha-transducin. Therefore alpha-gustducin was reconstituted with components of the visual system to determine the degree of its functional similarity with alpha-transducin. Despite the fact that the sequences of alpha-gustducin and alpha-transducin share only 80% identity with each other, the interactions and functions of these two proteins were quantitatively identical. These included the interaction with receptor, bovine rhodopsin, with effector, bovine retinal cyclic GMP-phosphodiesterase, and with bovine brain and retinal G-protein beta gamma-heterodimers; receptor-catalysed GDP-GTP exchange and the intrinsic GTPase activity of alpha-gustducin and alpha-transducin were also identical. Gi alpha which is 70% identical with alpha-transducin interacts with different receptor and effector proteins and has very different guanine-nucleotide binding properties. Therefore, the functional equivalence of alpha-gustducin and alpha-transducin suggest that taste buds are likely to contain receptor and effector proteins that share many properties with their retinal equivalents.
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Research Article| July 15 1995
Functional expression of the taste specific G-protein, α-gustducin
M A Hoon ;
J K Northup ;
R F Margolskee ;
Biochem J (1995) 309 (2): 629–636.
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M A Hoon, J K Northup, R F Margolskee, N J P Ryba; Functional expression of the taste specific G-protein, α-gustducin. Biochem J 15 July 1995; 309 (2): 629–636. doi: https://doi.org/10.1042/bj3090629
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