Chen Y, Saari J C, Noy N
Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853.
Biochemistry. 1993 Oct 26;32(42):11311-8. doi: 10.1021/bi00093a007.
Interphotoreceptor retinoid-binding protein (IRBP), a predominant protein in the interphotoreceptor matrix of the retina, has been implicated in transfer of retinoids between retinal pigment epithelium and photoreceptor cells. The interactions of IRBP with all-trans-retinol have been studied by three fluorescence-based methods and by measurements of binding of 3[H]-labeled all-trans-retinol to this protein. It was found that IRBP contains two sites with similar but not identical affinities for all-trans-retinol. The dissociation constant of the all-trans-retinol-IRBP complex at the first site was 0.1 microM, which is about 10-fold lower than previously reported values. The second site had about 2.5-fold lower affinity for all-trans-retinol as compared to the first site. Long-chain fatty acids were found in this study to displace all-trans-retinol from the stronger retinol-binding site on IRBP. Displacement of all-trans-retinol was used to study the interactions of fatty acids with this protein. It was found that docosahexaenoic acid (DHA C22:6n-3), an essential fatty acid which plays an important role in vision, had the highest apparent affinity for the site probed on IRBP of all the fatty acids studied.
光感受器间类视黄醇结合蛋白（IRBP）是视网膜光感受器间基质中的一种主要蛋白质，它与视网膜色素上皮细胞和光感受器细胞之间类视黄醇的转运有关。通过三种基于荧光的方法以及测量[3H]标记的全反式视黄醇与该蛋白质的结合，研究了IRBP与全反式视黄醇的相互作用。发现IRBP含有两个对全反式视黄醇具有相似但不相同亲和力的位点。全反式视黄醇 - IRBP复合物在第一个位点的解离常数为0.1 microM，比先前报道的值低约10倍。与第一个位点相比，第二个位点对全反式视黄醇的亲和力低约2.5倍。在本研究中发现长链脂肪酸可将全反式视黄醇从IRBP上较强的视黄醇结合位点置换出来。利用全反式视黄醇的置换来研究脂肪酸与该蛋白质的相互作用。结果发现，二十二碳六烯酸（DHA C22:6n-3）是一种在视觉中起重要作用的必需脂肪酸，在所研究的所有脂肪酸中，它对IRBP上被探测的位点具有最高的表观亲和力。
