Spontaneous activation of visual pigments in relation to openness/closedness of chromophore-binding pocket

Elife. 2017 Feb 10;6:e18492. doi: 10.7554/eLife.18492.


Visual pigments can be spontaneously activated by internal thermal energy, generating noise that interferes with real-light detection. Recently, we developed a physicochemical theory that successfully predicts the rate of spontaneous activity of representative rod and cone pigments from their peak-absorption wavelength (λmax), with pigments having longer λmax being noisier. Interestingly, cone pigments may generally be ~25 fold noisier than rod pigments of the same λmax, possibly ascribed to an 'open' chromophore-binding pocket in cone pigments defined by the capability of chromophore-exchange in darkness. Here, we show in mice that the λmax-dependence of pigment noise could be extended even to a mutant pigment, E122Q-rhodopsin. Moreover, although E122Q-rhodopsin shows some cone-pigment-like characteristics, its noise remained quantitatively predictable by the 'non-open' nature of its chromophore-binding pocket as in wild-type rhodopsin. The openness/closedness of the chromophore-binding pocket is potentially a useful indicator of whether a pigment is intended for detecting dim or bright light.

Keywords: mouse; neuroscience; retinal photoreceptors; spontaneous excitation; vision; visual pigment.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Chemical Phenomena
  • Mice
  • Retinal Cone Photoreceptor Cells / physiology*
  • Retinal Pigments / chemistry*
  • Retinal Pigments / metabolism*
  • Retinal Rod Photoreceptor Cells / physiology*


  • Retinal Pigments