Knöpfel Martin, Smith Craig, Solioz Marc
Department of Clinical Pharmacology, University of Berne, 3010 Berne, Switzerland.
Biochem Biophys Res Commun. 2005 May 13;330(3):645-52. doi: 10.1016/j.bbrc.2005.03.023.
The divalent metal ion transporter DMT1 is localized in the brush border membrane (BBM) of the upper small intestine and has been shown to be able to transport Mn2+, Fe2+, Co2+, Ni2+, and Cu2+. Belgrade rats have a glycine-to-arginine (G185R) mutation in DMT1, which affects its function. We investigated copper transport with BBM vesicles of Belgrade rats loaded with calcein, which exhibits fluorescence quenching by various metal ions. Transport of copper was disrupted in unenergized BBM vesicle of b/b Belgrade rats, as had been described for iron transport, while +/b vesicles exhibited normal transport by DMT1. When either b/b or +/b vesicles were loaded with ATP and magnesium, similar high-affinity accumulation of copper was observed in both types of vesicles. Thus, brush border membranes possess an ATP-driven, high-affinity copper transport system which could serve as the primary route for copper uptake by the intestine.
二价金属离子转运蛋白1(DMT1)定位于十二指肠的刷状缘膜(BBM),并且已证实其能够转运Mn2+、Fe2+、Co2+、Ni2+和Cu2+。贝尔格莱德大鼠的DMT1存在甘氨酸到精氨酸(G185R)的突变,这影响了其功能。我们用装载了钙黄绿素的贝尔格莱德大鼠的BBM囊泡研究了铜的转运,钙黄绿素会被各种金属离子淬灭荧光。正如铁转运的情况那样,b/b贝尔格莱德大鼠的无能量BBM囊泡中的铜转运受到破坏,而+/b囊泡通过DMT1表现出正常转运。当b/b或+/b囊泡装载ATP和镁时,在两种类型的囊泡中均观察到相似的高亲和力铜积累。因此,刷状缘膜拥有一个ATP驱动的高亲和力铜转运系统,该系统可作为肠道摄取铜的主要途径。