CTR1 also known as COPT1, SLC31A1 is a high-affinity copper transporter found in the cell membrane.CTR1 functions as a homotrimer to effect the uptake of dietary copper. A series of methionine-rich repeats and other residues are conserved among CTR1 genes across taxa, and are thought to be important for copper transport. In mammalian cells, CTR1 is localized to the plasma membrane and intracellular vesicles. Research studies suggest that the CTR1 copper transporter also mediates uptake of the anticancer drug cisplatin in yeast and mammals and that decreased CTR1 can result in the development of cisplatin resistance. Treatment of cancer cells with cisplatin can result in reduced CTR1 expression, which reduces cisplatin accumulation within cells and leads to cisplatin resistance in some human cancer cells.