Functional expression of the taste specific G-protein, alpha-gustducin

• Published in: Biochemical journal 1995-07, Vol.309 ( Pt 2) (2), p.629-636
• Main Authors: Hoon, M A, Northup, J K, Margolskee, R F, Ryba, N J
• Format: Article
• Language: English
• Subjects: 3',5'-Cyclic-AMP Phosphodiesterases - metabolism; Adenosine Diphosphate Ribose - metabolism; Animals; Baculoviridae - genetics; Base Sequence; Catalysis; Cell Line; Cloning, Molecular; DNA Primers; DNA, Complementary; Enzyme Activation; GTP Phosphohydrolases - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Molecular Sequence Data; Protein Binding; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Rhodopsin - metabolism; Spodoptera; Taste; Transducin - genetics; Transducin - isolation & purification; Transducin - metabolism; Virulence Factors, Bordetella - pharmacology
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3090629

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.