Ito Hiroyasu, Inouhe Masahiro, Tohoyama Hiroshi, Joho Masanori
Department of Biology, Faculty of Science, Ehime University, Matsuyama, Ehime, 790-8577, Japan.
Biometals. 2007 Oct;20(5):773-80. doi: 10.1007/s10534-006-9040-0. Epub 2006 Nov 18.
We discovered that a mutant strain of the dimorphic yeast Yarrowia lipolytica could grow in the yeast form in high concentrations of copper sulfate. The amount of metal accumulated by Y. lipolytica increased with increasing copper concentrations in the medium. Washing with 100 mM EDTA released at least 60% of the total metal from the cells, but about 20-25 micromol/g DW persisted, which represented about 30% of the soluble fraction of cultured cells. The soluble fraction (mainly cytosol) contained only about 10% of the total metal content within cells cultured in medium supplemented with 6 mM copper. We suggest that although a high copper concentration induces an efflux mechanism, the released copper becomes entrapped in the periplasm and in other parts of the cell wall. Washing with EDTA liberated not only copper ions, but also melanin, a brown pigment that can bind metal and which located at the cell wall. These findings indicated that melanin participates in the mechanism of metal accumulation. Culture in medium supplemented with copper obviously enhanced the activities of Cu, Zn-SOD, but not of Mn-SOD.
我们发现，双态酵母解脂耶氏酵母的一个突变菌株能够在高浓度硫酸铜中以酵母形式生长。解脂耶氏酵母积累的金属量随着培养基中铜浓度的增加而增加。用100 mM乙二胺四乙酸（EDTA）洗涤可从细胞中释放至少60%的总金属，但仍有约20 - 25微摩尔/克干重的金属残留，这约占培养细胞可溶部分的30%。在添加6 mM铜的培养基中培养的细胞，其可溶部分（主要是细胞质）仅含有细胞内总金属含量的约10%。我们认为，尽管高铜浓度诱导了一种外排机制，但释放出的铜会被困在周质和细胞壁的其他部分。用EDTA洗涤不仅释放了铜离子，还释放了黑色素，一种可结合金属且位于细胞壁的棕色色素。这些发现表明黑色素参与了金属积累机制。在添加铜的培养基中培养明显增强了铜锌超氧化物歧化酶（Cu, Zn - SOD）的活性，但对锰超氧化物歧化酶（Mn - SOD）的活性没有影响。
