Differential ability to form the G protein βγ complex among members of the β and γ subunit families

Kang Yan, Vani Kalyanaraman, Narasimhan Gautam

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87 Scopus citations


We have determined the relative abilities of several members of the G protein β and γ subunit families to associate with each other using the yeast two-hybrid system. We show first that the mammalian β1 and γ3 fusion proteins form a complex in yeast and that formation of the complex activates the reporter gene for β-galactosidase. Second, the magnitude of reporter activity stimulated by various combinations of β and γ subunit types varies widely. Third, the reporter activity evoked by a particular combination of β and γ subunit types is not correlated with the expression levels of these subunit types in the yeast cells. Finally, the reporter activity shows a direct relationship with the amount of hybrid βγ complex formed in the cell as determined by immunoprecipitation. These results suggest that different β and γ subunit types interact with each other with widely varying abilities, and this in combination with the level of expression of a subunit type in a mammalian cell determines which G protein will be active in that cell. The strong preference of all γ subunit types for the β1 subunit type explains the preponderence of this subunit type in most G proteins.

Original languageEnglish
Pages (from-to)7141-7146
Number of pages6
JournalJournal of Biological Chemistry
Issue number12
StatePublished - Mar 22 1996


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