Interactions of pure βγ‐subunits of G‐proteins with purified β₁‐adrenoceptor

Abstract

The role of the βγ‐subunits in the interaction of G‐proteins was examined with β1‐adrenoceptors purified from turkey erythrocytes and pure βγ‐subunits prepared from turkey erythrocytes and bovine brain. On a non‐denaturing polyacrylamide gel, the mobility of βγ‐subunits was increased when incubated with β1‐adrenoceptor and the β1‐adrenergic agonist l‐(−)‐isoproterenol, whereas on incubation with the antagonist l‐alprenolol the mobility was unchanged. Furthermore, the β1‐adrenoceptor was retarded on a Sephadex G‐50 column equilibrated with βγ‐subunits and agonist. No retardation occurred in the presence of antagonist. These data suggest a direct interaction of activated β1‐adrenoceptors with isolated βγ‐subunits of G‐proteins.

Subunit interactions of GTP‐binding proteins

“…Previously, we have shown that isolated bovine brain pisubunits can associate with the p,-adrenoceptor purified from turkey erythrocyte membranes (Im et al, 1988;Kurstjens et al, 1991). The j-adrenoceptor seems not to be the only hormone receptor which can couple to By-subunits.…”

Specific enhancement of beta-adrenergic receptor kinase activity by defined G-protein beta and gamma subunits.

“…5). For example, direct interactions of fry complexes with receptors have been shown by biochemical and biophysical means (6)(7)(8). The (By subunit complexes have also been shown to be capable of interacting with effectors.…”

Analysis of stimulation-G protein subunit coupling by using active insulin-like growth factor II receptor peptide.

“…Values represent means ± SE of three experiments. receptor (9). Also transducin fry subunit (T13)-induced enhancement of rhodopsin-transducin linkage reaches saturation at the To-, concentration lower than that of the transducin a subunit (Ta) (7), suggesting that Tpy acts catalytically on Ta.…”

“…However, direct interactions of receptors with Ga remain to be demonstrated by using purified proteins. Several reports indicate that Go, directly interacts with the /3-adrenergic receptor or rhodopsin (7)(8)(9); the possibility that Ga indirectly interacts with receptors through Gab remains. Furthermore, it is unclear whether Gay stoichiometrically or catalytically acts on the receptor-Ga linkage, although it has been shown that Gab enhances this linkage (10,11).…”