Distribution of interstitial retinol-binding protein (IRBP) in the vertebrates.
Immunoblots of interphotoreceptor matrix preparations from 20 species belonging to six vertebrate classes were probed with antibodies against bovine interstitial retinol-binding protein (b-IRBP). Each preparation displayed an immunoreactive protein band. In the Osteichthyes, the apparent Mr of this band was 67,600 +/- 2,700 (mean +/- SD, n = 8). In two of the Osteichthyes, the band was resolved into a closely spaced doublet. Including previously published data for five mammals and one amphibian, species from the other classes (Chondrichthyes, one species; Amphibia, four species; Reptilia, one species; Aves, one species; Mammalia, nine species) had IRBPs with Mr that averaged 2.0 times that of the Osteichthyes, namely 134,200 +/- 8,600 (mean +/- SD, n = 17). Frog IRBP was very similar to mammalian IRBP in terms of its immunohistochemical distribution (determined with rabbit anti-frog IRBP antibodies), its molecular weight (sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel-filtration chromatography), retinol- and concanavalin A-binding ability, and because it was synthesized and secreted in vitro by the isolated retina but not by the pigmented layers of eye. Goldfish IRBP apparently binds exogenous (3H)-retinol but does not bind concanavalin A and has about half the Mr of frog IRBP. The occurrence of IRBP-like proteins cross-reacting with anti b-IRBP antibodies in the interphotoreceptor matrix of all six major vertebrate classes is consistent with the hypothesis that IRBP is an important element in the vertebrate visual cycle.
D000818:Animals; D002417:Cattle; D002645:Chickens; D005399:Fishes; D006054:Goldfish; D006168:Guinea Pigs; D006801:Humans; D005779:Immunodiffusion; D008027:Light; D009799:Ocular Physiological Phenomena; D010786:Photoreceptor Cells / Q000166:cytology; D011817:Rabbits; D011821:Raccoons; D011894:Rana pipiens; D012177:Retinol-Binding Proteins / Q000032:analysis*; D012453:Saimiri; D013045:Species Specificity; D014426:Turtles; D014562:Caudata
D012177:Retinol-Binding Proteins