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Science. 1997 Jan 17;275(5298):381-4.

Receptor and betagamma binding sites in the alpha subunit of the retinal G protein transducin.

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Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143-0450, USA.

Erratum in

  • Science 1997 Apr 18;276(5311):341.


Transmembrane receptors for hormones, neurotransmitters, light, and odorants mediate their cellular effects by activating heterotrimeric guanine nucleotide-binding proteins (G proteins). Crystal structures have revealed contact surfaces between G protein subunits, but not the surfaces or molecular mechanism through which Galphabetagamma responds to activation by transmembrane receptors. Such a surface was identified from the results of testing 100 mutant alpha subunits of the retinal G protein transducin for their ability to interact with rhodopsin. Sites at which alanine substitutions impaired this interaction mapped to two distinct Galpha surfaces: a betagamma-binding surface and a putative receptor-interacting surface. On the basis of these results a mechanism for receptor-catalyzed exchange of guanosine diphosphate for guanosine triphosphate is proposed.

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