Transducin activation by rhodopsin without a covalent bond to the 11-cis-retinal chromophore

Science. 1991 Feb 1;251(4993):558-60. doi: 10.1126/science.1990431.

Abstract

Rhodopsin and the visual pigments are a distinct group within the family of G-protein-linked receptors in that they have a covalently bound ligand, the 11-cis-retinal chromophore, whereas all of the other receptors bind their agonists through noncovalent interactions. The retinal chromophore in rhodopsin is bound by means of a protonated Schiff base linkage to the epsilon-amino group of Lys-296. Two rhodopsin mutants have been constructed, K296G and K296A, in which the covalent linkage to the chromophore is removed. Both mutants form a pigment with an absorption spectrum close to that of the wild type when reconstituted with the Schiff base of an n-alkylamine and 11-cis-retinal. In addition, the pigment formed from K296G and the n-propylamine Schiff base of 11-cis-retinal was found to activate transducin in a light-dependent manner, with 30 to 40% of the specific activity measured for the wild-type protein. It appears that the covalent bond is not essential for binding of the chromophore or for catalytic activation of transducin.

Publication types

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

MeSH terms

  • Binding Sites
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Kinetics
  • Mutagenesis, Site-Directed
  • Protein Binding
  • Retinaldehyde / metabolism*
  • Rhodopsin / genetics
  • Rhodopsin / metabolism*
  • Rhodopsin / radiation effects
  • Schiff Bases
  • Spectrophotometry
  • Transducin / metabolism*
  • Transducin / radiation effects

Substances

  • Schiff Bases
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Rhodopsin
  • Transducin
  • Retinaldehyde