Luo Wenqin, Marsh-Armstrong Nicholas, Rattner Amir, Nathans Jeremy
Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Neurosci. 2004 Mar 17;24(11):2623-32. doi: 10.1523/JNEUROSCI.5302-03.2004.
Photoreceptor retinol dehydrogenase (prRDH) is a membrane-associated cytosolic protein that localizes to the outer segments (OS) of rods and cones. Here, we demonstrate that the C-terminal 16 amino acids of prRDH confer membrane association as well as cone and rod OS targeting on a linked green fluorescent protein. Membrane association in transfected 293 cells and in transgenic Xenopus photoreceptors is mediated by fatty acylation at one or more evolutionarily conserved cysteines within the prRDH C-terminal tail. In bovine OS, native prRDH is similarly acylated, and hydrolysis of this linkage releases the protein from the membrane. Efficient OS localization requires both membrane association and the prRDH sequence. (V/I)XPX at the extreme C terminus, which closely resembles the C-terminal sequence that targets opsin/rhodopsin to the OS. Taken together, these data imply that the C-terminal. (V/I)XPX sequence is a general OS localization signal that can function in the context of both integral and peripheral membrane proteins. This strategy for OS localization resembles those used for protein localization to mitochondria, peroxisomes, endosomes, and endoplasmic reticulum; in each case, a short N- or C-terminal sequence is shared among structurally diverse proteins that are targeted to the same subcellular destination.
光感受器视黄醇脱氢酶（prRDH）是一种与膜相关的胞质蛋白，定位于视杆细胞和视锥细胞的外段（OS）。在此，我们证明prRDH的C末端16个氨基酸赋予与膜的结合以及对连接的绿色荧光蛋白的视锥和视杆细胞外段靶向性。在转染的293细胞和转基因非洲爪蟾光感受器中的膜结合是由prRDH C末端尾巴内一个或多个进化保守的半胱氨酸处的脂肪酰化介导的。在牛的外段中，天然prRDH同样被酰化，这种连接的水解使蛋白质从膜上释放。有效的外段定位需要膜结合和prRDH序列。极端C末端的（缬氨酸/异亮氨酸）XPX，与将视蛋白/视紫红质靶向到外段的C末端序列非常相似。综上所述，这些数据表明C末端的（缬氨酸/异亮氨酸）XPX序列是一种通用的外段定位信号，可在整合膜蛋白和外周膜蛋白的背景下起作用。这种外段定位策略类似于用于蛋白质定位于线粒体、过氧化物酶体、内体和内质网的策略；在每种情况下，一个短的N末端或C末端序列在靶向相同亚细胞目的地的结构多样的蛋白质中共享。
