The rhodopsin-retinochrome system in invertebrate photoreceptors

在视觉色素的光化学和光能转导（包括光信号的放大）等方面对视觉中的分子碱基进行了深入的研究。除了这些问题之外，了解视觉细胞的光感受能力得以延续的背景也是非常有趣的。这个问题实际上包括光色素的再生和视网膜异构体在细胞内的流动。为此，我们最近分离了一个视网膜结合蛋白（RALBP），发现了一种以RALBP和元色素之间的发色团相互交换为特征的新型再生。这表明，在视觉细胞中，后视紫红质和后视黄色素可能最终通过RALBP的调解交换各自的发色团，从而再生视紫红质和视黄色素。在早期的视蛋白和异视黄色素膜实验中，我们证明了两种膜的紧密接触会导致视紫红质的形成，11-顺式视网膜转移到视蛋白膜中。这种来自横纹肌微绒毛和髓小体的膜最初在细胞内彼此相距很远，因此在这些结构之间有一些适合视网膜的穿梭体。事实上，根据生化和免疫细胞化学检查，上述RALBP的分布仅限于视觉细胞内。我们现在认为，最有可能的是，视网膜的RALBP和metarhotinochrome之间的交换反应在位于外节段基底区和内节段的髓系体上进行，而RALBP和metarhodopsin之间的交换反应在外节段的横纹肌上进行。我们还用分离的试管检查了视觉细胞中RALBP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，形成视网膜的再循环系统。我们称之为视紫红-视黄色素系统

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