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

Science. 1997 Jan 17;275(5298):381-4. doi: 10.1126/science.275.5298.381.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aluminum Compounds / pharmacology
  • Animals
  • Binding Sites
  • COS Cells
  • Fluorides / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Guanosine Diphosphate / metabolism
  • Models, Molecular
  • Mutation
  • Phenotype
  • Protein Conformation*
  • Retinaldehyde / pharmacology
  • Rhodopsin / metabolism*
  • Rhodopsin / pharmacology
  • Rod Cell Outer Segment / metabolism
  • Transducin / chemistry*
  • Transducin / metabolism


  • Aluminum Compounds
  • Guanosine Diphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Rhodopsin
  • Transducin
  • Fluorides
  • Retinaldehyde
  • aluminum fluoride