Overexpression of rhodopsin alters the structure and photoresponse of rod photoreceptors

Biophys J. 2009 Feb;96(3):939-50. doi: 10.1016/j.bpj.2008.10.016.


Rhodopsins are densely packed in rod outer-segment membranes to maximize photon absorption, but this arrangement interferes with transducin activation by restricting the mobility of both proteins. We attempted to explore this phenomenon in transgenic mice that overexpressed rhodopsin in their rods. Photon capture was improved, and, for a given number of photoisomerizations, bright-flash responses rose more gradually with a reduction in amplification--but not because rhodopsins were more tightly packed in the membrane. Instead, rods increased their outer-segment diameters, accommodating the extra rhodopsins without changing the rhodopsin packing density. Because the expression of other phototransduction proteins did not increase, transducin and its effector phosphodiesterase were distributed over a larger surface area. That feature, as well as an increase in cytosolic volume, was responsible for delaying the onset of the photoresponse and for attenuating its amplification.

Publication types

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

MeSH terms

  • Absorption
  • Animals
  • Cattle
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism
  • Fatty Acids / analysis
  • Gene Expression
  • Light*
  • Mice
  • Mice, Transgenic
  • Retinal Rod Photoreceptor Cells / chemistry*
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Retinal Rod Photoreceptor Cells / radiation effects
  • Rhodopsin / biosynthesis
  • Rhodopsin / genetics*
  • Rhodopsin / metabolism*
  • Rod Opsins / genetics


  • Fatty Acids
  • Rod Opsins
  • Rhodopsin