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The structure of the G protein heterotrimer Gi alpha 1 beta 1 gamma 2.


Wall MAM A , Coleman DE D E , Lee E E , IƱiguez-Lluhi JA J A , Posner BA B A , Gilman AG A G , Sprang SR S R . Cell. 1995 12 15; 83(6). 1047-58


The crystallographic structure of the G protein heterotrimer Gi alpha 1(GDP)beta 1 gamma 2 (at 2.3 A) reveals two nonoverlapping regions of contact between alpha and beta, an extended interface between beta and nearly all of gamma, and limited interaction of alpha with gamma. The major alpha/beta interface covers switch II of alpha, and GTP-induced rearrangement of switch II causes subunit dissociation during signaling. Alterations in GDP binding in the heterotrimer (compared with alpha-GDP) explain stabilization of the inactive conformation of alpha by beta gamma. Repeated WD motifs in beta form a circularized sevenfold beta propeller. The conserved cores of these motifs are a scaffold for display of their more variable linkers on the exterior face of each propeller blade.