How rods respond to single photons: Key adaptations of a G-protein cascade that enable vision at the physical limit of perception.
Rod photoreceptors are among the most sensitive light detectors in nature. They achieve their remarkable sensitivity across a wide variety of species through a number of essential adaptations: a specialized cellular geometry, a G-protein cascade with an unusually stable receptor molecule, a low-noise transduction mechanism, a nearly perfect effector enzyme, and highly evolved mechanisms of feedback control and receptor deactivation. Practically any change in protein expression, enzyme activity, or feedback control can be shown to impair photon detection, either by decreasing sensitivity or signal-to-noise ratio, or by reducing temporal resolution. Comparison of mammals to amphibians suggests that rod outer-segment morphology and the molecules and mechanism of transduction may have evolved together to optimize light sensitivity in darkness, which culminates in the extraordinary ability of these cells to respond to single photons at the ultimate limit of visual perception.
IBENS, Group of Computational Biology and Applied Mathematics, École Normale Supérieure, Paris, France.|INSERM U1024, Paris, France.
Jürgen
J
Reingruber
IBENS, Group of Computational Biology and Applied Mathematics, École Normale Supérieure, Paris, France.|Department of Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK.
David
D
Holcman
Department of Integrative Biology and Physiology, Terasaki Life Sciences, University of California, Los Angeles, CA, USA.|Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, CA, USA.
Gordon L
GL
Fain
D000222:Adaptation, Physiological; D000818:Animals; D002024:Bufo marinus / Q000502:physiology*; D006152:Cyclic GMP / Q000096:biosynthesis / Q000378:metabolism; D008027:Light; D008322:Mammals; D051379:Mice; D017785:Photons; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology
D012243:Rhodopsin; D006152:Cyclic GMP
G-protein receptor; phosphodiesterase; photoreceptors; retina; rhodopsin; rods; vision