The mitochondrial ornithine transporter - Bacterial expression, reconstitution, functional characterization, and tissue distribution of two human isoforms
The mitochondrial ornithine transporter - Bacterial expression, reconstitution, functional characterization, and tissue distribution of two human isoforms
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DOI：
10.1074/jbc.m302317200
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发表时间：
2003-08-29
影响因子：
4.8
通讯作者：
Walker, JE
中科院分区：
文献类型：
--
作者：
Fiermonte, G;Dolce, V;Walker, JE
人鸟氨酸载体的两种同种型，ORC 1和ORC 2，已经通过在细菌中蛋白质的过表达和通过研究重组到脂质体中的纯化蛋白质的转运特性而鉴定。两者都通过交换和单向机制转运鸟氨酸、赖氨酸、精氨酸和瓜氨酸的L-异构体，并且它们被相同的抑制剂灭活。ORC 2具有比ORC 1更宽的特异性，L-和D-组氨酸、L-高精氨酸以及鸟氨酸、赖氨酸和鸟氨酸的D-异构体都是底物。这两种蛋白质都在广泛的人体组织中表达，但ORC 1是主要形式。两种亚型的最高表达水平都在肝脏中。还制备了与人类疾病高鸟氨酸血症-高氨血症-高瓜氨酸尿症相关的五种突变形式的ORC 1。突变消除了蛋白质的运输特性。在患有高鸟氨酸血症-高氨血症-高瓜氨酸尿症的患者中，同种型ORC 2是未修饰的，并且其存在部分地补偿了ORC 1缺陷。
Two isoforms of the human ornithine carrier, ORC1 and ORC2, have been identified by overexpression of the proteins in bacteria and by study of the transport properties of the purified proteins reconstituted into liposomes. Both transport L-isomers of ornithine, lysine, arginine, and citrulline by exchange and by unidirectional mechanisms, and they are inactivated by the same inhibitors. ORC2 has a broader specificity than ORC1, and L- and D-histidine, L-homoarginine, and D-isomers of ornithine, lysine, and ornithine are all substrates. Both proteins are expressed in a wide range of human tissues, but ORC1 is the predominant form. The highest levels of expression of both isoforms are in the liver. Five mutant forms of ORC1 associated with the human disease hyperornithinemia-hyperammonemia- homocitrullinuria were also made. The mutations abolish the transport properties of the protein. In patients with hyperornithinemia-hyperammonemia-homocitrullinuria, isoform ORC2 is unmodified, and its presence compensates partially for defective ORC1.