Rhodopsin activation blocked by metal-ion-binding sites linking transmembrane helices C and F

Nature. 1996 Sep 26;383(6598):347-50. doi: 10.1038/383347a0.


A large superfamily of receptors containing seven transmembrane (TM) helices transmits hormonal and sensory signals across the plasma membrane to heterotrimeric G proteins at the cytoplasmic face of the membrane. To investigate how G-protein-coupled receptors work at the molecular level, we have engineered metal-ion-binding sites between TM helices to restrain activation-induced conformational change in specific locations. In rhodopsin, the photoreceptor of retinal rod cells, we substituted histidine residues for natural amino acids at the cytoplasmic ends of the TM helices C and F. The resulting mutant proteins were able to activate the visual G protein transducin in the absence but not in the presence of metal ions. These results indicate that the TM helices C and F are in close proximity and suggest that movements of these helices relative to one another are required for transducin activation. Thus a change in the orientations of TM helices C and F is likely to be a key element in the mechanism for coupling binding of ligands (or isomerization of retinal) to the activation of G-protein-coupled receptors.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cattle
  • Cell Line
  • Cell Membrane / metabolism
  • Cytoplasm / metabolism
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Histidine / genetics
  • Histidine / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Conformation
  • Protein Structure, Secondary
  • Receptors, Cell Surface / metabolism*
  • Rhodopsin / antagonists & inhibitors
  • Rhodopsin / chemistry
  • Rhodopsin / genetics
  • Rhodopsin / metabolism*
  • Spectrophotometry, Ultraviolet
  • Transducin / metabolism*
  • Zinc / metabolism*


  • Receptors, Cell Surface
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Histidine
  • Rhodopsin
  • Transducin
  • Zinc