Identification and metabolic role of the mitochondrial aspartate-glutamate transporter in Saccharomyces cerevisiae
Identification and metabolic role of the mitochondrial aspartate-glutamate transporter in Saccharomyces cerevisiae
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DOI：
10.1046/j.1365-2958.2003.03742.x
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发表时间：
2003-11-01
影响因子：
3.6
通讯作者：
Satrústegui, J
中科院分区：
文献类型：
--
作者：
Cavero, S;Vozza, A;Satrústegui, J
哺乳动物细胞中的苹果酸-天冬氨酸NADH穿梭需要线粒体谷氨酸-谷氨酸载体（AGC）的活性。最近，我们在人类中发现了两种AGC亚型，aralar 1和citrin，它们受线粒体内膜外表面钙离子的调节。我们现在已经确定Agc 1 p作为人类AGC的酵母对应物。相应的基因在细菌和酵母线粒体中过表达，蛋白质在脂质体中重组，根据其转运特性鉴定为谷氨酸-谷氨酸转运蛋白。此外，缺乏Agc 1 p的酵母细胞无法在乙酸和油酸上生长，并且缬氨酸，鸟氨酸和瓜氨酸的水平降低;相反，它们在乙醇上生长。人AGC亚型的表达可以取代Agc 1 p的功能。然而，与其人类直系同源物不同，酵母Agc 1 p催化谷氨酸盐-谷氨酸盐交换和底物单端口活动。我们得出结论，Agc 1 p在酿酒酵母中执行两个代谢作用。一方面，它作为单向转运蛋白为线粒体提供谷氨酸，用于氮代谢和鸟氨酸合成。另一方面，Agc 1 p作为谷氨酸盐-谷氨酸盐交换剂，在苹果酸盐-天冬氨酸盐NADH穿梭中起作用，这对于以乙酸盐和脂肪酸作为碳源的酵母生长至关重要。这些结果为酵母中存在苹果酸-天冬氨酸NADH穿梭提供了强有力的证据。
The malate-aspartate NADH shuttle in mammalian cells requires the activity of the mitochondrial aspartate-glutamate carrier (AGC). Recently, we identified in man two AGC isoforms, aralar1 and citrin, which are regulated by calcium on the external face of the inner mitochondrial membrane. We have now identified Agc1p as the yeast counterpart of the human AGC. The corresponding gene was overexpressed in bacteria and yeast mitochondria, and the protein was reconstituted in liposomes where it was identified as an aspartate-glutamate transporter from its transport properties. Furthermore, yeast cells lacking Agc1p were unable to grow on acetate and oleic acid, and had reduced levels of valine, ornithine and citrulline; in contrast they grew on ethanol. Expression of the human AGC isoforms can replace the function of Agc1p. However, unlike its human orthologues, yeast Agc1p catalyses both aspartate-glutamate exchange and substrate uniport activities. We conclude that Agc1p performs two metabolic roles in Saccharomyces cerevisiae. On the one hand, it functions as a uniporter to supply the mitochondria with glutamate for nitrogen metabolism and ornithine synthesis. On the other, the Agc1p, as an aspartate-glutamate exchanger, plays a role within the malate-aspartate NADH shuttle which is critical for the growth of yeast on acetate and fatty acids as carbon sources. These results provide strong evidence of the existence of a malate-aspartate NADH shuttle in yeast.