Identification of the mitochondrial glutamate transporter - Bacterial expression, reconstitution, functional characterization, and tissue distribution of two human isoforms
Identification of the mitochondrial glutamate transporter - Bacterial expression, reconstitution, functional characterization, and tissue distribution of two human isoforms
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DOI：
10.1074/jbc.m201572200
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发表时间：
2002-05-31
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;Palmieri, L;Walker, JE
线粒体载体是线粒体内膜中的转运蛋白家族。它们穿梭底物、代谢物和辅因子通过这层膜，并将细胞质功能与基质中的其他功能连接起来。谷氨酸与H+共转运（或交换为OH-），但没有蛋白质与这种活性相关。两个人类表达序列标签编码具有63%同一性的323和315个氨基酸的蛋白质，其与谷氨酸盐-谷氨酸盐载体（载体家族的成员）相关。它们在大肠杆菌中过表达并重组为磷脂囊泡。它们的运输特性表明，这两种蛋白质是过去在整个线粒体中描述的谷氨酸/H+同向转运体的同种型。亚型1在所有组织中的表达水平高于亚型2，但脑除外，脑中两种亚型的表达水平相当。两种亚型的表达水平和动力学参数的差异表明，亚型2与所有组织的基本要求相匹配，特别是在氨基酸降解方面，而亚型1变得可操作以适应与特定代谢功能如尿素生成相关的更高需求。
The mitochondrial carriers are a family of transport proteins in the inner membranes of mitochondria. They shuttle substrates, metabolites, and cofactors through this membrane and connect cytoplasm functions with others in the matrix. Glutamate is co-transported with H+ (or exchanged for OH-), but no protein has ever been associated with this activity. Two human expressed sequence tags encode proteins of 323 and 315 amino acids with 63% identity that are related to the aspartate-glutamate carrier, a member of the carrier family. They have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties demonstrate that the two proteins are isoforms of the glutamate/H+ symporter described in the past in whole mitochondria. Isoform 1 is expressed at higher levels than isoform 2 in all the tissues except in brain, where the two isoforms are expressed at comparable levels. The differences in expression levels and kinetic parameters of the two isoforms suggest that isoform 2 matches the basic requirement of all tissues especially with respect to amino acid degradation, and isoform 1 becomes operative to accommodate higher demands associated with specific metabolic functions such as ureogenesis.