Rhodopsin retinoid binding

The interphotoreceptor retinoid-binding protein (Borst et al., 1989) functions in the regeneration of rhodopsin in the mammalian visual cycle. It is exclusive to vertebrates yet contains a repeated structure that has been found singly in bacterial and plant tail-specific proteases (TSPc) (Silber et al., 1992) and the archaeal tricorn protease (Tamura et al., 1996). The eukaryotic homologs of TSPc are likely to be inactive as... 

Retinal antigens, such as S-antigen (arrestin), interphotoreceptor retinoid-binding protein (IRBP), rhodopsin, recoverin, and phosduscin, appear to hold uveitogenic properties. Immunization with these antigens or their fragments can induce... 

Pepperberg DR, Okajima TL, Wiggert B, Ripps H, Crouch RK, Chader GJ (1993) The role of interphotoreceptor retinoid-binding protein (IRBP) in the visual cycle of rhodopsin. Mol Neurobiol 7 61-84 Chen Y, Noy N (1994) Retinoid specificity of interphotoreceptor retinoid-binding protein. Biochemistry 33 10 658-10 665... 

Rhodopsin is a seven ot-helix trans-membrane protein and visual pigment of the vertebrate rod photoreceptor cells that mediate dim light vision. In this photoreceptor, retinal is the chromophore bound by opsin protein, covalently linked to Lys296 by a Schiff base linkage. Kpega et al.64 have studied NMR spectra of Schiff bases being derivatives of all-frans retinal and amino-p-cyclodextrins as a model of rhodopsin, where p-cyclodextrin plays a role of a binding pocket. On the basis of analysis of the chemical shift differences for the model compound in the presence and in the absence of adamantane carboxylate, it has been shown that the derivative of 3-amino-p-cyclodextrin forms dimer in water and retinoid is inserted into p-cyclodextrin cavity [31]. 

Opsin is the apoprotein of rhodopsin that can result from exposure of the protein to hght (termed bleached opsin) or from lack of the availability of the 11-ds retinal (termed virgin opsin) (Figure 127.4). There is, however, a physiological difference at these two forms of opsin. Bleached opsin is induced by light exposure of rhodopsin and is phosphorylated by rhodopsin kinase. Bleached opsin was shown to have residual activity that reduces visual sensitivity. On the other hand, the characteristics of opsin that has not previously bound 11-c/s retinal, because it was not available due to a disruption in the retinoid metaboHsm " and prior to its developmental occurrence, or because it was unable to bind the Hgand and form rhodopsin, are different from those of the opsin resulting from the photoactivation... 

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