A New Role for βy-Subunits of G-Proteins?

Abstract

The prevailing view of the role of βy-subunits in signal transmission of G-protein-linked hormone receptors ascribes to βy-subunits a role in facilitating the binding of the α-subunits in heterotrimeric G-proteins in the inactive GDP-bound form to the receptor (cf: Bourne et al. 1990). In addition, there is good evidence that βy-subunits serve as anchors in membrane attachment of G-proteins (Sternweis 1986). The evidence which is now presented supports a role of βy-subunits in the attachment of α-subunits to the β-adrenoceptor and, moreover, indicates that separate βy-subunits can also bind to the activated (Im et al. 1988) and to the non-activated β-receptor as well. These findings suggest that the β-receptor may form a long-lived complex with βy-subunits alone. As that may be, this complex does not seem to dissociate with activation when the α-subunit charged with GTP[S] is discharged from the receptor. A detailed account of this work is in press (Kurstjens et al. 1990).