AgtA, the Dicarboxylic Amino Acid Transporter of Aspergillus nidulans, Is Concertedly Down-Regulated by Exquisite Sensitivity to Nitrogen Metabolite Repression and Ammonium-Elicited Endocytosis
AgtA, the Dicarboxylic Amino Acid Transporter of Aspergillus nidulans, Is Concertedly Down-Regulated by Exquisite Sensitivity to Nitrogen Metabolite Repression and Ammonium-Elicited Endocytosis
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DOI：
10.1128/ec.00270-08
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发表时间：
2009-03-01
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影响因子：
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通讯作者：
Sophianopoulou, Vicky
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作者：
Apostolaki, Angeliki;Erpapazoglou, Zoi;Sophianopoulou, Vicky
我们确定了agtA，一个基因，编码特定的二羧酸氨基酸转运蛋白构巢曲霉。该基因的缺失导致天冬氨酸作为氮源的利用和天冬氨酸吸收的损失，而不完全废除谷氨酸的利用。动力学常数表明，AgtA是一种高亲和力的二羧酸氨基酸转运蛋白，并与先前确定的同源转运蛋白活性一致。该基因对氮代谢物阻遏极其敏感，依赖于AreA的表达，并且似乎独立于特异性诱导。我们发现，定位在质膜上的AgtA需要的ShrA蛋白和铵引起的结果在内化和AgtA的液泡，随后降解的目标，一个积极的过程。因此，氮代谢物阻遏和铵促进的液泡降解作用一致下调二羧酸的运输活性。
We identified agtA, a gene that encodes the specific dicarboxylic amino acid transporter of Aspergillus nidulans. The deletion of the gene resulted in loss of utilization of aspartate as a nitrogen source and of aspartate uptake, while not completely abolishing glutamate utilization. Kinetic constants showed that AgtA is a high-affinity dicarboxylic amino acid transporter and are in agreement with those determined for a cognate transporter activity identified previously. The gene is extremely sensitive to nitrogen metabolite repression, depends on AreA for its expression, and is seemingly independent from specific induction. We showed that the localization of AgtA in the plasma membrane necessitates the ShrA protein and that an active process elicited by ammonium results in internalization and targeting of AgtA to the vacuole, followed by degradation. Thus, nitrogen metabolite repression and ammonium-promoted vacuolar degradation act in concert to downregulate dicarboxylic amino acid transport activity.