Fischer W N, Kwart M, Hummel S, Frommer W B
Institut für Genbiologische Forschung, Berlin, Germany.
J Biol Chem. 1995 Jul 7;270(27):16315-20. doi: 10.1074/jbc.270.27.16315.
Three amino acid transporter genes (AAP3-5) were isolated from Arabidopsis by complementation of a yeast mutant defective in histidine uptake. Transport is driven against a concentration gradient and sensitive to protonophores. Analysis of the substrate specificity demonstrates that the carriers have a broad substrate specificity covering the major transport forms of reduced nitrogen, i.e. glutamine and glutamate. The transporters have similar affinities for glutamate, glutamine, and alanine but differ with respect to valine, phenylalanine, histidine, arginine, and lysine. AAP3 and AAP5 efficiently transport arginine and lysine and are involved in basic amino acid transport. The predicted polypeptides of 53 kDa are highly hydrophobic with 12 putative membrane-spanning regions and show significant homologies to Arabidopsis amino acid transporters AAP1 and AAP2. Each of the genes has a different organ-specific expression in the plant. AAP3 is exclusively expressed in roots and AAP4 mainly in source leaves, stems, and flowers, whereas AAP5 is found in all tissues. The specific distribution in the plant and the different substrate specificities of AAP transporters may indicate that tissues differ both qualitatively and quantitatively regarding import or export of amino acids.
通过对组氨酸摄取缺陷的酵母突变体进行互补，从拟南芥中分离出三个氨基酸转运蛋白基因（AAP3 - 5）。转运过程是逆浓度梯度进行的，并且对质子载体敏感。底物特异性分析表明，这些载体具有广泛的底物特异性，涵盖了还原态氮的主要转运形式，即谷氨酰胺和谷氨酸。这些转运蛋白对谷氨酸、谷氨酰胺和丙氨酸具有相似的亲和力，但在缬氨酸、苯丙氨酸、组氨酸、精氨酸和赖氨酸方面存在差异。AAP3和AAP5能有效转运精氨酸和赖氨酸，并参与碱性氨基酸的转运。预测的53 kDa多肽具有高度疏水性，有12个假定的跨膜区域，与拟南芥氨基酸转运蛋白AAP1和AAP2具有显著同源性。每个基因在植物中都有不同的器官特异性表达。AAP3仅在根中表达，AAP4主要在源叶、茎和花中表达，而AAP5在所有组织中都有表达。AAP转运蛋白在植物中的特定分布和不同的底物特异性可能表明，不同组织在氨基酸的输入或输出方面在质和量上都存在差异。
