Carboxyl terminal of G protein beta subunit is required for association with gamma subunit

To investigate a complex formation of heterotrimeric G protein beta and gamma subunits, we constructed a deletion mutant which lacked the C-terminal WD40 repeating unit of beta 1 and cotransfected into HEK293 cells with gamma 2 which was tagged with FLAG-epitope. Co-immunoprecipitation assay indicated that the mutant beta 1 failed to associate with FLAG gamma 2. Furthermore, from the analysis of additional deletion mutants, the last 10 amino acids of C-terminal region of beta 1 were found to be necessary to associate with gamma 2. These results suggest that the C-terminal region, in addition to the N-terminal alpha-helical structure, of beta subunit may be involved in the beta gamma complex formation.