Department of Biological Sciences, The University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA.
Biometals. 2019 Aug;32(4):695-705. doi: 10.1007/s10534-019-00206-3. Epub 2019 Jul 10.
Copper-zinc superoxide dismutase (Sod1) is a critical antioxidant enzyme that rids the cell of reactive oxygen through the redox cycling of a catalytic copper ion provided by its copper chaperone (Ccs). Ccs must first acquire this copper ion, directly or indirectly, from the influx copper transporter, Ctr1. The three proteins of this transport pathway ensure careful trafficking of copper ions from cell entry to target delivery, but the intricacies remain undefined. Biochemical examination of each step in the pathway determined that the activation of the target (Sod1) regulates the Ccs·Ctr1 interaction. Ccs stably interacts with the cytosolic C-terminal tail of Ctr1 (Ctr1c) in a copper-dependent manner. This interaction becomes tripartite upon the addition of an engineered immature form of Sod1 creating a stable Cu(I)-Ctr1c·Ccs·Sod1 heterotrimer in solution. This heterotrimer can also be made by the addition of a preformed Sod1·Ccs heterodimer to Cu(I)-Ctr1c, suggestive of multiple routes to the same destination. Only complete Sod1 activation (i.e. active site copper delivery and intra-subunit disulfide bond formation) breaks the Sod1·Ccs·Ctr1c complex. The results provide a new and extended view of the Sod1 activation pathway(s) originating at cellular copper import.
铜锌超氧化物歧化酶（Sod1）是一种关键的抗氧化酶，通过其铜伴侣（Ccs）提供的催化铜离子的氧化还原循环，清除细胞中的活性氧。Ccs 必须首先直接或间接地从流入铜转运体 Ctr1 中获取这种铜离子。该运输途径的三种蛋白质确保了铜离子从细胞进入到靶标的精心运输，但细节仍未定义。对该途径中每一步的生化检查表明，靶标（Sod1）的激活调节 Ccs·Ctr1 相互作用。Ccs 以铜依赖性方式与 Ctr1 的细胞质 C 末端尾巴（Ctr1c）稳定相互作用。在添加工程化的不成熟形式的 Sod1 后，这种相互作用变为三部分，在溶液中形成稳定的 Cu（I）-Ctr1c·Ccs·Sod1 杂三聚体。通过将预先形成的 Sod1·Ccs 异二聚体添加到 Cu（I）-Ctr1c 中，也可以制成这种杂三聚体，表明存在多种到达同一目的地的途径。只有完全的 Sod1 激活（即活性部位铜的传递和亚单位中二硫键的形成）才能打破 Sod1·Ccs·Ctr1c 复合物。结果提供了一个新的和扩展的 Sod1 激活途径（多个）的观点，该途径起源于细胞内铜的输入。
