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首页> 外文期刊>American Journal of Physiology >Identification and characterization of a novel family of membrane magnesium transporters, MMgTl and MMgT2
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Identification and characterization of a novel family of membrane magnesium transporters, MMgTl and MMgT2

机译：新型膜镁转运蛋白MMgT1和MMgT2的鉴定和表征

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First published December 5, 2007; doi:10.1152/ajpcell.00238.2007.-Magnesium is an essential metal, but few selective transporters have been identified at the molecular level. Microarray analysis was used to identify two similar transcripts that are upregulated with low extracellular Mg~(2+). The corresponding cDNAs encode proteins of 131 and 123 amino acids with two predicted transmembrane domains. The two separate gene products comprise the family that we have termed "membrane Mg~(2+) transporters" (MMgTs), because the proteins reside in the membrane and mediate Mg~(2+) transport. When expressed in Kenopus laevis oocytes, MMgTl and MMgT2 mediate Mg~(2+) transport as determined with two-electrode voltage-clamp analysis and fluorescence measurements. Transport is saturable Mg~(2+) uptake with Michaelis constants of 1.47 +- 0.17 and 0.58 +- 0.07 mM, respectively. Real-time RT-PCR demonstrated that MMgT mRNAs are present in a wide variety of cells. Subcellular localization with immunohistochemistry determined that the MMgTl-hemagglutinin (HA) and MMgT2-V5 fusion proteins reside in the Golgi complex and post-Golgi vesicles, including the early endosomes in COS-7 cells transfected with the respective tagged constructs. Interestingly, MMgTl-HA and MMgT2-V5 were found in separate populations of post-Golgi vesicles. MMgTl and MMgT2 mRNA increased by about threefold, respectively, in kidney epithelial cells cultured in low-magnesium media relative to normal media and in the kidney cortex of mice maintained on low-magnesium diets compared with those animals consuming normal diets. With the increase in transcripts, there was an apparent increase in MMgTl and MMgT2 protein in the Golgi and post-Golgi vesicles. These experiments suggest that MMgT proteins may provide regulated pathways for Mg~(2+) transport in the Golgi and post-Golgi organelles of epithelium-derived cells.
机译：首次发布于2007年12月5日; doi：10.1152 / ajpcell.00238.2007.-镁是必不可少的金属，但在分子水平上几乎没有发现选择性转运蛋白。微阵列分析用于鉴定两个相似的转录本，这些转录本的细胞外Mg〜（2+）低。相应的cDNAs编码131和123个氨基酸的蛋白质，并带有两个预测的跨膜结构域。这两个独立的基因产物组成了我们称为“膜Mg〜（2+）转运蛋白”（MMgTs）的家族，因为蛋白质驻留在膜中并介导Mg〜（2+）转运。当在金缕鱼卵母细胞中表达时，MMgT1和MMgT2介导Mg〜（2+）转运，如通过两电极电压钳分析和荧光测量所确定。迁移是饱和的Mg〜（2+）吸收，其Michaelis常数分别为1.47±0.17和0.58±0.07 mM。实时RT-PCR证明MMgT mRNA存在于多种细胞中。免疫组织化学的亚细胞定位确定MMgT1-血凝素（HA）和MMgT2-V5融合蛋白存在于高尔基复合体和高尔基体后囊泡中，包括用相应标记构建体转染的COS-7细胞中的早期内体。有趣的是，在高尔基后小泡的不同群体中发现了MMgT1-HA和MMgT2-V5。相对于正常培养基，在低镁饮食中维持的小鼠的肾上皮细胞中和在低镁饮食中维持的小鼠的肾皮质中，MMgT1和MMgT2 mRNA分别增加约三倍。随着转录物的增加，高尔基体和高尔基体后囊泡中的MMgT1和MMgT2蛋白明显增加。这些实验表明，MMgT蛋白可能为上皮来源的细胞的高尔基体和高尔基体后细胞器中的Mg〜（2+）转运提供调控的途径。

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