Daniel Hannelore, Rubio-Aliaga Isabel
Molecular Nutrition Unit, Technical University of Munich, D-85350 Freising-Weihenstephan, Germany.
Am J Physiol Renal Physiol. 2003 May;284(5):F885-92. doi: 10.1152/ajprenal.00123.2002.
The brush-border membrane of renal epithelial cells contains PEPT1 and PEPT2 proteins that are rheogenic carriers for short-chain peptides. The carrier proteins display a distinct surface expression pattern along the proximal tubule, suggesting that initially di- and tripeptides, either filtered or released by surface-bound hydrolases from larger oligopeptides, are taken up by the low-affinity but high-capacity PEPT1 transporter and then by PEPT2, which possesses a higher affinity but lower transport capacity. Both carriers transport essentially all possible di- and tripeptides and numerous structurally related drugs. A unique feature of the mammalian peptide transporters is the capability of proton-dependent electrogenic cotransport of all substrates, regardless of their charge, that is achieved by variable coupling in proton movement along with the substrate down the transmembrane potential difference. This review focuses on the postcloning research efforts to understand the molecular physiology of peptide transport processes in renal tubules and summarizes available data on the underlying genes, protein structures, and transporter function as derived from studies in heterologous expression systems.
肾上皮细胞的刷状缘膜含有PEPT1和PEPT2蛋白，它们是短链肽的生电载体。这些载体蛋白沿近端小管呈现出独特的表面表达模式，这表明最初由表面结合的水解酶从较大的寡肽中滤过或释放的二肽和三肽，先被低亲和力但高容量的PEPT1转运体摄取，然后被亲和力较高但转运能力较低的PEPT2摄取。这两种载体基本上能转运所有可能的二肽和三肽以及许多结构相关的药物。哺乳动物肽转运体的一个独特特征是能够对所有底物进行质子依赖性生电共转运，无论其电荷如何，这是通过质子运动与底物沿着跨膜电位差的可变偶联来实现的。本综述重点关注克隆后为了解肾小管中肽转运过程的分子生理学所做的研究工作，并总结了来自异源表达系统研究的关于相关基因、蛋白质结构和转运体功能的现有数据。
