Jin Minghao, Li Songhua, Moghrabi Walid N, Sun Hui, Travis Gabriel H
Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, California 90095, USA.
Cell. 2005 Aug 12;122(3):449-59. doi: 10.1016/j.cell.2005.06.042.
The first event in light perception is absorption of a photon by an opsin pigment, which induces isomerization of its 11-cis-retinaldehyde chromophore. Restoration of light sensitivity to the bleached opsin requires chemical regeneration of 11-cis-retinaldehyde through an enzymatic pathway called the visual cycle. The isomerase, which converts an all-trans-retinyl ester to 11-cis-retinol, has never been identified. Here, we performed an unbiased cDNA expression screen to identify this isomerase. We discovered that the isomerase is a previously characterized protein called Rpe65. We confirmed our identification of the isomerase by demonstrating catalytic activity in mammalian and insect cells that express Rpe65. Mutations in the human RPE65 gene cause a blinding disease of infancy called Leber congenital amaurosis. Rpe65 with the Leber-associated C330Y and Y368H substitutions had no isomerase activity. Identification of Rpe65 as the isomerase explains the phenotypes in rpe65-/- knockout mice and in humans with Leber congenital amaurosis.
光感知的首个事件是视蛋白色素吸收一个光子，这会诱导其11-顺式视黄醛发色团发生异构化。恢复对漂白视蛋白的光敏感性需要通过一种称为视觉循环的酶促途径对11-顺式视黄醛进行化学再生。将全反式视黄酯转化为11-顺式视黄醇的异构酶从未被鉴定出来。在此，我们进行了一项无偏向性的cDNA表达筛选以鉴定这种异构酶。我们发现该异构酶是一种先前已被表征的名为Rpe65的蛋白质。我们通过在表达Rpe65的哺乳动物和昆虫细胞中证明其催化活性，证实了我们对该异构酶的鉴定。人类RPE65基因的突变会导致一种婴儿期致盲疾病，称为莱伯先天性黑蒙。具有与莱伯相关的C330Y和Y368H替换的Rpe65没有异构酶活性。将Rpe65鉴定为异构酶解释了rpe65-/-基因敲除小鼠以及患有莱伯先天性黑蒙的人类的表型。
