Enhancement of opsin activity by all-trans-retinal

Exp Eye Res. 1998 May;66(5):599-603. doi: 10.1006/exer.1997.0453.


The rod cell photoreceptor apoprotein, opsin, activates the G-protein, transducin, although at a much reduced level than light-activated rhodopsin. The ability of all-trans-retinal to enhance opsin apoprotein activity was investigated using a guanyl nucleotide exchange assay on transducin. All-trans-retinal enhanced opsin activity in a concentration-dependent manner. At high concentrations of all-trans-retinal, the activity of the all-trans-retinal-opsin complex was comparable to that from an equimolar amount of metarhodopsin(II). However, in contrast to metarhodopsin(II), the active all-trans-retinalopsin complex did not require a stable Schiff base linkage between opsin and all-trans-retinal. The lack of a stable Schiff base and differences in activity at high pH imply that opsin and all-trans-retinal form a complex that is distinct from metarhodopsin(II). The ability of all-trans-retinal to stimulate the transduction cascade may be a source of post-bleach noise in photoreceptors.

Publication types

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

MeSH terms

  • Animals
  • Cattle
  • Dose-Response Relationship, Drug
  • Hydrogen-Ion Concentration
  • Protein Denaturation
  • Retinaldehyde / pharmacology*
  • Rhodopsin / analogs & derivatives
  • Rhodopsin / metabolism
  • Rod Cell Outer Segment / metabolism*
  • Rod Opsins / metabolism*
  • Schiff Bases / metabolism
  • Transducin / metabolism
  • Vision, Ocular


  • Rod Opsins
  • Schiff Bases
  • metarhodopsins
  • Rhodopsin
  • Transducin
  • Retinaldehyde