To test the proteins for photoreactivity, we first measured the "dark" absorbance of the protein, e.g., the naive protein that has been incubated and regenerated with the chromophore (11-cis retinal
or all-trans retinal).
(14) In the normal functioning retina vitamin A is transported from Bruch's membrane to reach the retinal pigment epithelium (RPE) where it is converted to 11-cis retinal
and combines with the protein opsin which ultimately forms rhodopsin in the photoreceptor outer segments (see Figure 4, page 70).
Retinal epithelial (RPE) cells perform multiple functions to maintain retinal homeostasis, including preserving the blood-retinal barrier, nourishing retinal cells by secreting growth factors [1, 2], phagocytosis of shed photoreceptor outer segments [3, 4], and maintenance of the visual cycle by resynthesizing 11-cis retinal
Topics addressed include photoreceptor membrane conductance, how the retinal pigment epithelium (RPE) regenerates 11-cis retinal
, photoreceptor adaptation to various levels of illumination and the biochemical basis of this phenomenon as well as its psychophysical consequences, how the retina develops into its final structure, how signals are processed in the retinal synaptic layers, and how changes in the retina and RPE influence normal aging.
SWS2, P434 opsin was expressed in COS cells, and the pigment formed with the A1 chromophore, 11-cis retinal
, showed absorption [1.sub.max] of 434 nm.
It is caused by mutations in RDH5, encoding 11-cis-retinol dehydrogenase , and leads to impaired production of 11-cis retinal
, restricting the photopigment turnover and leading to reduced formation of lipofuscin .