Liu W, Liang R, Ramamoorthy S, Fei Y J, Ganapathy M E, Hediger M A, Ganapathy V, Leibach F H
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912, USA.
Biochim Biophys Acta. 1995 May 4;1235(2):461-6. doi: 10.1016/0005-2736(95)80036-f.
Mammalian kidney is known to express a transport system specific for small peptides and pharmacologically active aminocephalosporins. This system is energized by a transmembrane electrochemical H+ gradient. Recently, a H(+)-coupled peptide transporter has been cloned from rabbit and human intestine (Fei et al. (1994) Nature 368, 563-566; Liang et al., J. Biol. Chem., in press). Functional studies have established that the renal peptide transport system is similar but not identical to its intestinal counterpart. Therefore, in an attempt to isolate the renal H+/peptide cotransporter cDNA, we screened a human kidney cDNA library with a probe derived from the rabbit intestinal H+/peptide cotransporter cDNA. This has resulted in the isolation of a positive clone with a 2190 bp long open reading frame. The predicted protein consists of 729 amino acids. Hydropathy analysis of the amino acid sequence indicates the presence of twelve putative transmembrane domains. The primary structure of this protein exhibits 50% identity and 70% similarity to the human intestinal H+/peptide cotransporter. Functional expression of the kidney cDNA in HeLa cells results in the induction of a H(+)-coupled transport system specific for small peptides and aminocephalosporins. Reverse transcription-coupled polymerase chain reaction demonstrates that the cloned transporter is expressed in human kidney but not in human intestine. This transporter, henceforth called PEPT 2, represents a new member in the growing family of H(+)-coupled transport systems in the mammalian plasma membrane.
已知哺乳动物肾脏表达一种对小肽和具有药理活性的氨基头孢菌素具有特异性的转运系统。该系统由跨膜电化学H⁺梯度供能。最近，已从兔和人肠道中克隆出一种H⁺偶联肽转运体（Fei等人，(1994)《自然》368, 563 - 566；Liang等人，《生物化学杂志》，即将发表）。功能研究表明，肾脏肽转运系统与其肠道对应物相似但并不相同。因此，为了分离肾脏H⁺/肽共转运体cDNA，我们用源自兔肠道H⁺/肽共转运体cDNA的探针筛选了人肾脏cDNA文库。这导致分离出一个具有2190 bp长开放阅读框的阳性克隆。预测的蛋白质由729个氨基酸组成。对氨基酸序列的亲水性分析表明存在12个假定的跨膜结构域。该蛋白质的一级结构与人类肠道H⁺/肽共转运体具有50%的同一性和70%的相似性。肾脏cDNA在HeLa细胞中的功能表达导致诱导出一种对小肽和氨基头孢菌素有特异性的H⁺偶联转运系统。逆转录 - 聚合酶链反应表明，克隆的转运体在人肾脏中表达，但在人肠道中不表达。这种转运体，此后称为PEPT 2，代表了哺乳动物质膜中不断增加的H⁺偶联转运系统家族中的一个新成员。
