TY - JOUR
T1 - Breaking the covalent bond - A pigment property that contributes to desensitization in cones
AU - Kefalov, Vladimir J.
AU - Estevez, Maureen E.
AU - Kono, Massahiro
AU - Goletz, Patrice W.
AU - Crouch, Rosalie K.
AU - Cornwall, M. Carter
AU - Yau, King Wai
N1 - Funding Information:
This paper is dedicated to the memory of Edward (Ted) MacNichol, whose apparatus was used for some of the microspectrophotometric (MSP) experiments. We thank Dr. David Cameron for help in the collection and analysis of some early MSP data and Dr. Clint Makino for the use of his MSP instrument, Dr. Barbara Wiggert for a generous gift of IRBP, and Dr. John Crabb for the gift of the CRALBP expression vector. Members of the Yau laboratory have provided invaluable comments on the work and manuscript. Supported by NIH EY 06837 and the Ruth and Milton Steinbach Fund (K.-W.Y.), EY 01157 (M.C.C.), EY 04939 (R.K.C.), EY 13748 (M.K.), and an unrestricted grant to the Department of Ophthalmology, MUSC from Research to Prevent Blindness.
PY - 2005/6/16
Y1 - 2005/6/16
N2 - Retinal rod and cone pigments consist of an apoprotein, opsin, covalently linked to a chromophore, 11-cis retinal. Here we demonstrate that the formation of the covalent bond between opsin and 11-cis retinal is reversible in darkness in amphibian red cones, but essentially irreversible in red rods. This dissociation, apparently a general property of cone pigments, results in a surprisingly large amount of free opsin - about 10% of total opsin - in dark-adapted red cones. We attribute this significant level of free opsin to the low concentration of intracellular free 11-cis retinal, estimated to be only a tiny fraction (∼0.1 %) of the pigment content in red cones. With its constitutive transducin-stimulating activity, the free cone opsin produces an ∼2-fold desensitization in red cones, equivalent to that produced by a steady light causing 500 photoisomerizations s-1. Cone pigment dissociation therefore contributes to the sensitivity difference between rods and cones.
AB - Retinal rod and cone pigments consist of an apoprotein, opsin, covalently linked to a chromophore, 11-cis retinal. Here we demonstrate that the formation of the covalent bond between opsin and 11-cis retinal is reversible in darkness in amphibian red cones, but essentially irreversible in red rods. This dissociation, apparently a general property of cone pigments, results in a surprisingly large amount of free opsin - about 10% of total opsin - in dark-adapted red cones. We attribute this significant level of free opsin to the low concentration of intracellular free 11-cis retinal, estimated to be only a tiny fraction (∼0.1 %) of the pigment content in red cones. With its constitutive transducin-stimulating activity, the free cone opsin produces an ∼2-fold desensitization in red cones, equivalent to that produced by a steady light causing 500 photoisomerizations s-1. Cone pigment dissociation therefore contributes to the sensitivity difference between rods and cones.
UR - https://www.scopus.com/pages/publications/20444371505
U2 - 10.1016/j.neuron.2005.05.009
DO - 10.1016/j.neuron.2005.05.009
M3 - Article
C2 - 15953417
AN - SCOPUS:20444371505
SN - 0896-6273
VL - 46
SP - 879
EP - 890
JO - Neuron
JF - Neuron
IS - 6
ER -