Interaction between G-protein β and γ subunit types is selective

A. N. Pronin, N. Gautam

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128 Scopus citations


Signal-transducing guanine nucleotide-binding proteins (G proteins) are made up of three subunits, α, β, and γ. 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 (G(t)), the G protein in rod photoreceptors, most purified G proteins contain more than one subtype of β or γ subunits. The G(t) α subunit is associated only with β1 and γ1. 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 β and γ subunit types. We have used a transfected cell assay system to examine the association of the β1, β2, and β3 proteins with the γ1 and γ2 proteins. Results show that γ1 does not associate with β2 and that β3 does not associate with γ1 or γ2. 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 β1 and β2 was used to broadly map the regions on these subunits that determine specificity of association.

Original languageEnglish
Pages (from-to)6220-6224
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number13
StatePublished - 1992


  • signal transduction
  • subunit families


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