Coblenz A, Wolf K
Institut für Biologie IV (Mikrobiologie), Rheinisch-Westfälische Technische Hochschule Aachen, FRG.
FEMS Microbiol Rev. 1994 Aug;14(4):303-8. doi: 10.1111/j.1574-6976.1994.tb00103.x.
Plants and the fission yeast Schizosaccharomyces pombe synthesize small cadmium-binding peptides, called phytochelatins, in response to cadmium. Derived from glutathione (GSH: gamma-Glu-Cys-Gly), they have the general structure (gamma-Glu-Cys)nGly, where n is 2-11. In order to study the biosynthesis of phytochelatins, we used the mutagen N-methyl-N'-nitro-N nitrosoguanidine (MNNG) to select mutants with a lowered GSH content. GSH-deficient mutants show a Cd-sensitive phenotype, whereas resistance to Cu is only slightly influenced. These Cd-sensitive mutants contain 2-15% of the wild-type GSH level. For three mutants a lowered activity of gamma-glutamylcysteine synthetase was measured. One of the mutants was transformed to Cd-resistance and the complementing fragment was analyzed further. The complementing fragment hybridized with chromosome III. In the transformants, GSH content was restored up to wild-type levels, whereas the activity of gamma-glutamylcysteine synthetase was significantly increased compared with the wild-type. Possible mechanisms for Cd-resistance in the transformants are discussed.
植物和裂殖酵母粟酒裂殖酵母会响应镉合成一种名为植物螯合肽的小镉结合肽。它们由谷胱甘肽（GSH：γ-谷氨酰-半胱氨酰-甘氨酸）衍生而来，具有一般结构（γ-谷氨酰-半胱氨酰）n甘氨酸，其中n为2至11。为了研究植物螯合肽的生物合成，我们使用诱变剂N-甲基-N'-硝基-N-亚硝基胍（MNNG）来筛选谷胱甘肽含量降低的突变体。谷胱甘肽缺陷型突变体表现出对镉敏感的表型，而对铜的抗性仅受到轻微影响。这些对镉敏感的突变体的谷胱甘肽水平为野生型的2%至15%。对于三个突变体，测定了γ-谷氨酰半胱氨酸合成酶的活性降低。其中一个突变体被转化为对镉具有抗性，并对互补片段进行了进一步分析。互补片段与第三条染色体杂交。在转化体中，谷胱甘肽含量恢复到野生型水平，而γ-谷氨酰半胱氨酸合成酶的活性与野生型相比显著增加。讨论了转化体中对镉抗性的可能机制。
