衣藻在锌(Zn)有限的培养基中的生长导致铜(Cu)稳态的破坏,相对于其典型的铜配额,导致铜过度积累高达40倍。我们证明衣藻通过平衡铜进出口来控制其铜配额,在缺乏锌的细胞中被破坏,从而建立了铜和锌稳态之间的机械联系。转录组学,蛋白质组学和元素谱分析表明,锌限制衣藻细胞上调编码参与硫(S)同化的“第一反应者”蛋白质的基因子集,因此积累更多的细胞内S,结合到L-半胱氨酸中,γ-谷氨酰半胱氨酸和高半胱氨酸。最突出的是,在没有锌的情况下,游离的L-半胱氨酸增加了80倍,相当于2.8×109个分子/细胞。有趣的是,经典的含S金属结合配体,如谷胱甘肽和植物螯合素不会增加。X射线荧光显微镜显示与Cu共定位的锌限制细胞中S积累的焦点,磷和钙,与酸钙中的Cu-硫醇络合物一致,Cu(I)积累位点。值得注意的是,以前缺乏铜的细胞不会积累S或Cys,将半胱氨酸合成与Cu积累因果关系。我们建议半胱氨酸是体内Cu(I)配体,也许是祖先,缓冲细胞溶质铜。
Growth of Chlamydomonas reinhardtii in zinc (Zn) limited medium leads to disruption of copper (Cu) homeostasis, resulting in up to 40-fold Cu over-accumulation relative to its typical Cu quota. We show that Chlamydomonas controls its Cu quota by balancing Cu import and export, which is disrupted in a Zn deficient cell, thus establishing a mechanistic connection between Cu and Zn homeostasis. Transcriptomics, proteomics and elemental profiling revealed that Zn-limited Chlamydomonas cells up-regulate a subset of genes encoding \"first responder\" proteins involved in sulfur (S) assimilation and consequently accumulate more intracellular S, which is incorporated into L-cysteine, γ-glutamylcysteine, and homocysteine. Most prominently, in the absence of Zn, free L-cysteine is increased ∼80-fold, corresponding to ∼2.8 × 109 molecules/cell. Interestingly, classic S-containing metal binding ligands like glutathione and phytochelatins do not increase. X-ray fluorescence microscopy showed foci of S accumulation in Zn-limited cells that co-localize with Cu, phosphorus and calcium, consistent with Cu-thiol complexes in the acidocalcisome, the site of Cu(I) accumulation. Notably, cells that have been previously starved for Cu do not accumulate S or Cys, causally connecting cysteine synthesis with Cu accumulation. We suggest that cysteine is an in vivo Cu(I) ligand, perhaps ancestral, that buffers cytosolic Cu.