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How rods respond to single photons: Key adaptations of a G‐protein cascade that enable vision at the physical limit of perception
Author(s) -
Reingruber Jürgen,
Holcman David,
Fain Gordon L.
Publication year - 2015
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.201500081
Subject(s) - cascade , transduction (biophysics) , biophysics , effector , photon , sensitivity (control systems) , noise (video) , negative feedback , rod , signal transduction , biology , biological system , signal (programming language) , physics , optics , chemistry , microbiology and biotechnology , computer science , artificial intelligence , medicine , alternative medicine , engineering , chromatography , quantum mechanics , voltage , electronic engineering , pathology , image (mathematics) , programming language
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.