Soleimani M, Bizal G L
Department of Medicine, Indiana University, Indianapolis, USA.
Kidney Int. 1996 Dec;50(6):1914-21. doi: 10.1038/ki.1996.513.
Based on the transport activities and inhibitor sensitivities, different functional modes of anion exchangers have been identified in the kidney proximal tubule including chloride/formate, chloride/oxalate, chloride/hydroxyl, and chloride/bicarbonate exchange. There is little information on the molecular structure and properties of the protein(s) involved in these processes. Previously, using stilbene affinity matrix and Pac Q chromatography, we partially purified a protein with anion exchange properties in brush border membranes (BBM) isolated from rabbit kidney proximal tubules. This protein has a molecular weight of 162 kDa. When reconstituted into liposomes, the fraction containing the 162 kDa protein demonstrated Cl-/Cl- exchange activity. In the current experiments, the 162 kDa protein was purified to homogeneity using a combination of affinity, ion exchange, and size exclusion chromatography. This protein has binding affinity for known inhibitors of anion exchangers. When reconstituted in liposomes, the 162 kDa protein showed anion exchange activity as assayed by 36Cl-/Cl- exchange. Functional studies in liposomes reconstituted with the purified 162 kDa protein in revealed that this protein mediates the transport of Cl-/formate and Cl-/HCO3-. The Cl-/formate and Cl-/HCO3- exchange activities in the reconstituted liposomes were inhibited in the presence of DIDS and furosemide, two known inhibitors of renal anion exchangers. We conclude that Cl-/formate exchange and and Cl-/HCO3- exchange in kidney proximal tubules are mediated via the same protein. This protein is distinct from the known anion exchanger proteins (AE1, AE2, and AE3) and may represent another isoform from this family of transporters.
基于转运活性和抑制剂敏感性，已在肾近端小管中鉴定出阴离子交换体的不同功能模式，包括氯/甲酸根、氯/草酸根、氯/氢氧根和氯/碳酸氢根交换。关于参与这些过程的蛋白质的分子结构和特性，目前所知甚少。此前，我们利用芪亲和基质和Pac Q色谱法，从兔肾近端小管分离的刷状缘膜（BBM）中部分纯化了一种具有阴离子交换特性的蛋白质。该蛋白质的分子量为162 kDa。当重组成脂质体时，含有162 kDa蛋白质的组分表现出Cl⁻/Cl⁻交换活性。在当前实验中，通过亲和、离子交换和尺寸排阻色谱法相结合，将162 kDa蛋白质纯化至同质。该蛋白质对已知的阴离子交换体抑制剂具有结合亲和力。当重组成脂质体时，162 kDa蛋白质通过³⁶Cl⁻/Cl⁻交换测定显示出阴离子交换活性。用纯化的162 kDa蛋白质重组成的脂质体的功能研究表明，该蛋白质介导Cl⁻/甲酸根和Cl⁻/HCO₃⁻的转运。在存在二异丁基氨磺酰（DIDS）和呋塞米（两种已知的肾阴离子交换体抑制剂）的情况下，重组成的脂质体中的Cl⁻/甲酸根和Cl⁻/HCO₃⁻交换活性受到抑制。我们得出结论，肾近端小管中的Cl⁻/甲酸根交换和Cl⁻/HCO₃⁻交换是由同一种蛋白质介导的。该蛋白质不同于已知的阴离子交换体蛋白（AE1、AE2和AE3），可能代表该转运体家族的另一种异构体。
