MOLECULAR BIOLOGY OF OUTER RETINA-SPECIFIC PROTEINS

视网膜色素上皮（RPE）细胞和光感受器（PR）细胞是 功能和发展紧密结合。 我们 表征膜相关的65kD RPE特异性蛋白， 疏水的，并且取决于洗涤剂对其的增溶作用。 萃取 在细胞分级分离实验中，这种蛋白质存在于 微粒体沉淀。 获得了其氨基酸分析结果， 几种胰蛋白酶和胰凝乳蛋白酶肽的序列。 其氨基 终点站被封锁了。 我们已经克隆了这种蛋白的cDNA， 编码一种533个残基的蛋白质，与数据库中的任何其他蛋白质都不同。 光感受器间类维生素A结合蛋白（IRBP）参与 类维生素A的运输，RPE之间的功能关系， 我们已经亚克隆了DNA片段， 将牛IRBP的完整重复序列插入细菌表达载体中。 的 检测所得表达蛋白片段的类视色素， 绑定功能。其中一个片段，包括中央 两次重复结合视黄醇 这一发现表明，所有四个重复 的IRBP不是类视色素结合活性所必需的。 的结合 似乎定位于IRBP蛋白的中心区域。

Retinal pigment epithelial (RPE) cells and photoreceptor (PR) cells are functionally and developmentally closely integrated. We are characterizing a 65 kD RPE-specific protein that is membrane-associated, hydrophobic, and dependent upon detergent solubilization for its extraction. In cell fractionation experiments this protein is found in the microsomal pellet. We have obtained its amino acid analysis and the sequences of several tryptic and chymotryptic peptides. Its amino terminus is blocked. We have cloned cDNA for this protein, which encodes a 533-residue protein unlike any others in the data base. The interphotoreceptor retinoid-binding protein (IRBP) is involved in the transport of retinoids, a functional relationship between the RPE and the PR. We have subcloned DNA fragments corresponding to integral repeats of bovine IRBP into a bacterial expression vector. The resultant expressed protein fragments were tested for their retinoid- binding functions. One of the fragments, which comprises the central two repeats, bound retinol. This finding indicates that all four repeats of IRBP are not required for retinoid-binding activity. The binding appears to be localized to the central region of the IRBP protein.