DOES SUBUNIT DISSOCIATION NECESSARILY ACCOMPANY THE ACTIVATION OF ALLHETEROTRIMERIC G-PROTEINS

Heterotrimeric (alpha beta gamma) G proteins mediate a variety of sign al transduction events in virtually every cell of every eukaryotic org anism. The predominant hypothesis is that dissociation of the alpha-su bunit from the G beta gamma-subunit complex necessarily accompanies th e activation of these proteins, and that the alpha-subunit is primaril y responsible for regulating the response of effector molecules. Howev er, there is increasing evidence that both the alpha-subunit and the b eta gamma-subunit complex function in regulating effector activity. Fu rthermore, data for some G proteins suggest that they function as acti vated heterotrimers rather than as dissociated subunits. (C) 1997 Else vier Science Inc.