Takahashi T, Paliwal V K, Ebadi M
Department of Pharmacology, University of Nebraska College of Medicine, 42nd Street and Dewey Avenue, Omaha, NE 68105, U.S.A.
Neurochem Int. 1988;13(4):525-30. doi: 10.1016/0197-0186(88)90084-8.
The mammalian retinas contain the highest concentrations of Zn in any known living tissues. Metallothionein is a low-molecular-weight, cysteine-rich metal-binding protein which occurs ubiquitously in nature and which has been recently identified in mammalian brains with a high affinity to bind Zn. In order to study the metabolism of Zn further, we have measured its subcellular distribution in the bovine retina and have found the distribution to be nonuniform, with the outer rod segments and the pellet 1 fraction, known to be highly enriched in photoreceptor cell synaptosomes, containing the highest amounts of 0.230 +/- 0.040 and 0.119 +/- 0.04 ? Zn/mg protein, respectively. In addition, the bovine retina contains a low-molecular-weight metallothionein-like protein which exhibits an elution volume (V(c)/V(0)) of 1.9 on gel permeation chromatography and which produces only one isoform on reverse-phase high performance liquid chromatography with a retention time of 16.67 min. The precise function of this metallothioneinlike protein, which may be related to the transport and compartmentation of Zn in the retina, remains to be elucidated.
在所有已知的活组织中，哺乳动物的视网膜含锌量最高。金属硫蛋白是一种低分子量、富含半胱氨酸的金属结合蛋白，它在自然界中普遍存在，最近在哺乳动物大脑中被发现，对锌具有高亲和力。为了进一步研究锌的代谢，我们测量了锌在牛视网膜中的亚细胞分布，发现其分布不均匀，在已知富含光感受器细胞突触体的外视杆段和沉淀1组分中，锌含量最高，分别为0.230±0.040和0.119±0.04μg锌/毫克蛋白。此外，牛视网膜含有一种低分子量的类金属硫蛋白，在凝胶渗透色谱上其洗脱体积（V(c)/V(0)）为1.9，在反相高效液相色谱上只产生一种异构体，保留时间为16.67分钟。这种类金属硫蛋白的确切功能可能与视网膜中锌的运输和区室化有关，仍有待阐明。
