Functional expression of the taste specific G-protein, alpha-gustducin.
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.
Hoon
M A
MA
Laboratory of Immunology, National Institute of Dental Research, N.I.H., Bethesda, MD 20892, USA.
Northup
J K
JK
Margolskee
R F
RF
Ryba
N J
NJ
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D002384:Catalysis; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D018411:Spodoptera; D013649:Taste; D015293:Transducin / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D017931:DNA Primers; D018076:DNA, Complementary; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; C075192:gustducin; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D012243:Rhodopsin; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D020558:GTP Phosphohydrolases; D015293:Transducin