The rhodopsin-retinochrome system in invertebrate photoreceptors

视觉的分子基础研究主要集中在视色素的光化学和包括光信号放大在内的光能传递过程中。除了这些问题之外，了解使视觉细胞的感光能力得以延续的背景也是令人着迷的。这样的问题实际上包括细胞内色素的再生和视网膜异构体的流动。对此，我们最近分离了一种视网膜结合蛋白（RALBP），并发现了一种新的再生类型，其特征在于RALBP和元色素之间的发色团相互交换。这表明，在视细胞中，视紫红质和视黄色素可能最终通过RALBP的介导交换各自的发色团，以再生视紫红质和视黄色素。 ...更多信息 S导致视紫红质的形成，11-顺式-视黄醇转移到视蛋白膜中。这些膜来源于横纹肌微绒毛和髓样小体，它们在细胞内的位置原本相距很远，因此，人们认为在这些结构之间会有某种合适的视网膜穿梭物。事实上，上述RALBP的分布仅限于视觉细胞内，如生化和免疫细胞化学检查所示。我们认为RALBP与后视黄色素之间的视网膜交换反应很可能在位于外节基底区和内节的髓样体上进行，而RALBP与后视紫红质之间的视网膜交换反应则在外节的横纹肌上进行。用离体的离体视杯观察RALBP在视细胞内的运动细节。结果，这两个交换反应通过RALBP的往返连接成一个，形成了视网膜的再循环系统。我们称之为视紫红质-视色素系统

Many studies of molecular bases in vision have been developed in the photochemistry of visual pigments and the light energy transduction including amplification of photosignals. In addition to these problems, it is also fascinating to understand the background which makes possible the continuation of photoreceptive capacity of visual cell. Such a problem virtually includes the regeneration of photopigments and the flow of retinal isomers within the cell. With regard to this, we recently isolated a retinal-binding protein (RALBP), and found a new type of the regeneration characterized by the mutual exchange of chromophores between RALBP and meta-pigment. This suggested a possibility that, in the visual cells, metarhodopsin and metaretinochrome may eventually interchange their own chromophores through the mediation of RALBP to regenerate rhodopsin and retinochrome.In earlier experiments with opsin and metaretinochrome membranes, we demonstrated that the close contact of both the membrane … More s resulted in the formation of rhodopsin, the 11-cis-retinal transferred into the opsin membranes. Such membranes derived from the rhabdomal microvilli and the myeloid bodies are originally situated so far away from each other within the cell that some suitable shuttle for retinal was expected to serve between those structures. In fact, the distribution of RALBP described above is restricted to within the visual cells, as suggested by biochemical and immunocytochemical examinations. We now think that most likely, the exchange reaction of retinal between RALBP and metaretinochrome proceeds on the myeloid bodies which locate in the basal regins of the outer segments as well as in the inner segments, while that between RALBP and metarhodopsin proceeds on the rhabdomeres in the outer segments. The details of the movement of RALBP in the visual cells were also examined by using isolated exycups. As the result, those two exchange reactions is joined into one by a round trip of RALBP to form the recycling system of retinal. We shall call it the rhodopsin-retinochrome system Less