Goldfish cones secrete a two-repeat interphotoreceptor retinoid-binding protein.
Goldfish cones secrete a two-repeat interphotoreceptor retinoid-binding protein.
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金鱼视锥细胞分泌两次重复的光感受器间视黄醇结合蛋白。
DOI：
10.1007/bf00175823
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发表时间：
1995
影响因子：
3.9
通讯作者：
Gonzalez-Fernandez,F
中科院分区：
文献类型：
--
作者：
Wagenhorst,BB;Rajendran,RR;VanNiel,EE;Hessler,RB;Bukelman,A;Gonzalez-Fernandez,F
维生素A和脂肪酸对光感受器的结构、功能和发育至关重要。这些营养物质在色素上皮和神经视网膜之间的运输是由光感受器间类视黄酮结合蛋白（IRBP）介导的。IRBP是一种133 kda（人）糖脂蛋白，是分离这两个细胞层的细胞外基质的主要蛋白质成分。在两栖动物和哺乳动物中，IRBP由大约300个氨基酸的4个同源重复组成，形成2个视黄醇和4个脂肪酸结合位点。在这里，我们发现硬骨鱼中的IRBP是一种仅由两个重复组成的更简单的蛋白质。Western blot分析显示，金鱼IRBP的大小为高等脊椎动物IRBP的一半（70 kDa）。利用Brefeldin A进行的代谢标记研究、原位杂交研究和信号肽的存在表明，金鱼IRBP是由视锥光感受器分泌的。翻译的氨基酸序列计算分子量为66.7 kDa。初级结构只有两个同源重复序列，相似度为52.5%。人类和金鱼irbp的最后重复序列相似度为69.1%，其中疏水区域最相似。这些数据表明，在鳍鱼（放线鱼科）的进化过程中丢失了两个重复序列，或者在硬骨鱼（骨鱼科）和两栖动物的出现之间重复了IRBP基因。获得多重复结构可能反映了在有限空间内有效运输更高水平疏水分子的进化压力。祖先IRBP基因的四倍复制可能是高等脊椎动物光感受器进化过程中的一个重要事件。
Vitamin A and fatty acids are critical to photoreceptor structure, function, and development. The transport of these nutrients between the pigment epithelium and neural retina is mediated by interphotoreceptor retinoid-binding protein (IRBP). IRBP, a 133-kDa (human) glycolipoprotein, is the major protein component of the extracellular matrix separating these two cell layers. In amphibians and mammals, IRBP consists of four homologous repeats of about 300 amino acids which form two retinol and four fatty acid-binding sites. Here we show that IRBP in teleosts is a simpler protein composed of only two repeats. Western blot analysis shows that goldfish IRBP is half the size (70 kDa) of IRBP in higher vertebrates. Metabolic labeling studies employing Brefeldin A taken together with in situ hybridization studies and the presence of a signal peptide show that goldfish IRBP is secreted by the cone photoreceptors. The translated amino acid sequence has a calculated molecular weight of 66.7 kDa. The primary structure consists of only two homologous repeats with a similarity score of 52.5%. The last repeats of human and goldfish IRBPs are 69.1% similar with hydrophobic regions being the most similar. These data suggest that two repeats were lost during the evolution of the ray-finned fish (Actinopterygii), or that the IRBP gene duplicated between the emergence of bony fish (Osteichthyes) and amphibians. Acquisition of a multirepeat structure may reflect evolutionary pressure to efficiently transport higher levels of hydrophobic molecules within a finite space. Quadruplication of an ancestral IRBP gene may have been an important event in the evolution of photoreceptors in higher vertebrates.