图1. 拟南芥COPT的亚细胞定位与Cu的转运(改自Rodríguez et al., 1999; Balandin and Castresana, 2002; Wintz et al., 2003; Yruela, 2009; Garcia et al., 2014)
Cu²⁺可以被ZIP蛋白吸收或被FRO还原为Cu⁺, Cu⁺通过COPT1、COPT2和COPT6蛋白转运进入细胞质。在细胞内, COPT5定位于液泡膜和液泡前体膜, 将液泡和液泡前体中的Cu⁺转运到细胞质基质中。推测COPT3定位于内质网膜, 并将内质网中的Cu⁺转运到细胞质基质中。HMA6和HMA1分别定位于叶绿体外膜和内膜, 分别负责将Cu⁺和Cu²⁺转运到叶绿体基质。HMA8定位于类囊体膜上, 可将叶绿体基质的Cu⁺转运到类囊体腔中。HMA7能够转运Cu⁺通过高尔基体膜, 参与乙烯反应。HMA5定位于细胞膜, 介导Cu⁺的外排。

Figure 1. Subcellular localization of COPT and copper traffic in Arabidopsis (modified from Rodríguez et al., 1999; Balandin and Castresana, 2002; Wintz et al., 2003; Yruela, 2009; Garcia et al., 2014)
Cu²⁺can be uptaken by ZIP proteins or reduced to Cu⁺ by FRO and enters into the cytosol through the COPT1, COPT2 and COPT6 transporters. In the cell, COPT5 localizes in the tonoplast and vacuolar precursor membranes and transports Cu⁺ to the cytosol. It is speculated that COPT3 localizes to the ER membrane and transports Cu⁺ to the cytosol. HMA6 and HMA1 are localized in the membranes of the chloroplast and responsible for transporting Cu⁺ and Cu²⁺ to the cytosol, respectively. HMA8 is located in the thylakoid membrane and transports the Cu⁺ of the stroma into the thylakoid cavity. HMA7 transports Cu⁺ through the golgi membrane and participating in the ethylene reaction. HMA5 localizes in the cell membrane and mediates the efflux of Cu⁺.