Zhou H, Thiele D J
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
J Biol Chem. 2001 Jun 8;276(23):20529-35. doi: 10.1074/jbc.M102004200. Epub 2001 Mar 26.
Copper is an essential nutrient that serves as a co-factor for enzymes involved in critical cellular processes including energy generation, peptide hormone maturation, oxidative stress protection, and iron homeostasis. Although genes have been identified from yeast and mammals encoding a homologous subunit of a plasma membrane high affinity copper transporter, the presence of additional subunits that function as part of a copper transport complex has not been reported. We observed that ctr4(+), a previously identified copper transport protein from the fission yeast Schizosaccharomyces pombe, fails to complement bakers' yeast cells defective in high affinity copper transport and fails to be targeted to the plasma membrane. However, selection for S. pombe genes, which, when co-expressed with Ctr4, confer high affinity copper transport to S. cerevisiae cells resulted in the identification of ctr5(+). Both Ctr4 and Ctr5 are integral membrane proteins, are co-regulated by copper levels and the copper-sensing transcription factor Cuf1, physically associate in vivo, are interdependent for secretion to the plasma membrane, and are each essential for high affinity copper transport. These studies in S. pombe identify Ctr4 and Ctr5 as components of a novel eukaryotic heteromeric plasma membrane complex that is essential for high affinity copper transport.
铜是一种必需营养素，作为参与关键细胞过程的酶的辅助因子，这些过程包括能量生成、肽激素成熟、氧化应激保护和铁稳态。尽管已经从酵母和哺乳动物中鉴定出编码质膜高亲和力铜转运蛋白同源亚基的基因，但尚未报道作为铜转运复合体一部分发挥作用的其他亚基的存在。我们观察到，ctr4(+)是先前从粟酒裂殖酵母中鉴定出的一种铜转运蛋白，它不能补充高亲和力铜转运缺陷的面包酵母细胞，也不能靶向质膜。然而，筛选与Ctr4共表达时能赋予酿酒酵母细胞高亲和力铜转运能力的粟酒裂殖酵母基因，结果鉴定出了ctr5(+)。Ctr4和Ctr5都是整合膜蛋白，受铜水平和铜感应转录因子Cuf1共同调控，在体内物理结合，分泌到质膜相互依赖，且对高亲和力铜转运均必不可少。在粟酒裂殖酵母中的这些研究将Ctr4和Ctr5鉴定为一种新型真核异源质膜复合体的组成部分，该复合体对高亲和力铜转运至关重要。
