[Structure and function of heterotrimeric G-proteins].
In mammals, G-protein alpha, beta, gamma polypeptides are encoded by at least 16, 4 and 7 genes, respectively. G alpha-subunits bind and hydrolyze GTP and have the sites for bacterial toxin-catalyzed ADP-ribosylation. A structural model of G alpha-subunits can be defined on the basis of similarities between G alpha and other members of the GTP-binding proteins. The resulting G alpha model specifies the spatial relationship among the guanine nucleotide binding site, the binding site of the G beta gamma-subunit complex, likely regions of effector and receptor interaction, and sites of cholera or pertussis toxin-induced modification. The architecture of the G alpha core is the same as that of p21ras. Experimental evidence from immunological, molecular genetic and biochemical studies support the G alpha model. The G alpha-subunits alone were previously thought to act on the effector enzymes; However, recent evidence indicates that the G beta gamma-dimer also plays an important part in effector activation.
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
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Hoshino
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Katada
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation
D019204:GTP-Binding Proteins