Conklin D S, McMaster J A, Culbertson M R, Kung C
Laboratory of Molecular Biology, University of Wisconsin, Madison 53706.
Mol Cell Biol. 1992 Sep;12(9):3678-88. doi: 10.1128/mcb.12.9.3678-3688.1992.
The COT1 gene of Saccharomyces cerevisiae has been isolated as a dosage-dependent suppressor of cobalt toxicity. Overexpression of the COT1 gene confers increased tolerance to cobalt and rhodium ions but not other divalent cations. Strains containing null alleles of COT1 are viable yet more sensitive to cobalt than are wild-type strains. Transcription of COT1 responds minimally to the extracellular cobalt concentration. Addition of cobalt ions to growth media results in a twofold increase in COT1 mRNA abundance. The gene encodes a 48-kDa protein which is found in mitochondrial membrane fractions of cells. The protein contains six possible membrane-spanning domains and several potential metal-binding amino acid residues. The COT1 protein shares 60% identity with the ZRC1 gene product, which confers resistance to zinc and cadmium ions. Cobalt transport studies indicate that the COT1 product is involved in the uptake of cobalt ions yet is not solely responsible for it. The increased tolerance of strains containing multiple copies of the COT1 gene is probably due to increased compartmentalization or sequestration of the ion within mitochondria.
酿酒酵母的COT1基因已作为钴毒性的剂量依赖性抑制因子被分离出来。COT1基因的过表达赋予了对钴离子和铑离子更强的耐受性，但对其他二价阳离子则不然。含有COT1无效等位基因的菌株是存活的，但比野生型菌株对钴更敏感。COT1的转录对细胞外钴浓度的反应很小。向生长培养基中添加钴离子会导致COT1 mRNA丰度增加两倍。该基因编码一种48 kDa的蛋白质，这种蛋白质存在于细胞的线粒体膜组分中。该蛋白质含有六个可能的跨膜结构域和几个潜在的金属结合氨基酸残基。COT1蛋白与赋予对锌离子和镉离子抗性的ZRC1基因产物具有60%的同一性。钴转运研究表明，COT1产物参与钴离子的摄取，但并非唯一负责摄取的因素。含有多个COT1基因拷贝的菌株耐受性增强可能是由于离子在线粒体内的分隔或隔离增加所致。
