Interaction between G-protein beta and gamma subunit types is selective.
Signal-transducing guanine nucleotide-binding proteins (G proteins) are made up of three subunits, alpha, beta, and gamma. Each of these subunits comprises a family of proteins. The rules for association between members of one family with members of another to form a multimer are not known; it is not clear whether associations are specific or nonspecific. Other than transducin (Gt), the G protein in rod photoreceptors, most purified G proteins contain more than one subtype of beta or gamma subunits. The Gt alpha subunit is associated only with beta 1 and gamma 1. It is not known whether this specificity is due to the differential expression of these subunit types in a cell type or due to intrinsically different affinities between different beta and gamma subunit types. We have used a transfected cell assay system to examine the association of the beta 1, beta 2, and beta 3 proteins with the gamma 1 and gamma 2 proteins. Results show that gamma 1 does not associate with beta 2 and that beta 3 does not associate with gamma 1 or gamma 2. Differences in affinities between types of G protein subunits will impose restrictions on the formation of certain heterotrimers and determine which G protein will be active in a cell. A chimeric molecule of beta 1 and beta 2 was used to broadly map the regions on these subunits that determine specificity of association.
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Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110.
Gautam
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D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003370:Coturnix; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008798:Mevalonic Acid / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011994:Recombinant Proteins; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014162:Transfection
D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins; D008798:Mevalonic Acid