Abstract
The effect of metallothionein expression on the metal resistance and removal by recombinant Saccharomyces cerevisiae containing the plasmid pJW9 was investigated. The recombinant strain S. cerevisiae BZ-pJ was constructed by transforming the host strain S. cerevisiae BZ3l-1-7Ba with the gene coding for a metal-binding protein, metallothionein. Introduction of the MT gene yielded an increase in the minimum inhibitory concentration (MIC) of copper more than three times compared with the host strain. The minimum inhibitory concentrations of $Cr^{2+}, Znr^{2+} and Pb^{2+}, $ were not different for the two strains. The recombinant yeast grown in a medium containing 8mM CuSO4 was able to remove copper with a capacity of 18.9mg $Cu^{2+}$/g dry cell. In a mixture of copper and zinc, the presence of copper relieved the toxic effects caused by zinc, resulting in an enhancement of the final cell density and the specific growth rate of the recombinant yeast. The capability to remove copper by the recombinant yeast was linearly proportional to the copper concentrations in the medium. The efficiency of copper removal was rather constant regardless of the initial copper concentrations. The specific removal of zinc was dependent on the zinc concentrations in media, though, and such dependence was not so pronounced as the concentration of copper.
금속결합 단백질인 metallothionein (MT) 유전자 의 발현이 효모의 중금속 내성과 제거 특성에 미치는 영향을 살펴보았다 MT유전자로 형질전환된 재조합 효모는 숙주세포에 비해서 $Cu^{2+}$내성이 3배 이상 증가하였으나, $Cr^{2+}, Pb^{2+}, Znr^{2+}$에 대한 내성은 숙주세포와 별차이가 없었다. 재조합효모는 8mM $CuSP_4$를 함유하며 포도당을 탄소원으로 한 배지에서 18.9mg $Cu^{2+}$/g dry cell로 $Cu^{2+}$를 제거하였다. $Cu^{2+} 와 Zn^{2+}$의 훈합배지에서 $Cu^{2+}$가 존재함으로써 $Zn^{2+}$이 효모에 미치는 독성을 완하시켜 효모의 생육 속도와 최종균체농도를 증가시켰다. 재조합효모의 $Cu^{2+}$ 제거량은 배지중 $Cu^{2+}$농도에 비례하였다. $Cu^{2+}$ 농도가 2배, 3배 증가할 때 균체 g당 $Cu^{2+}$제거량은 각각 2.3배, 3.1배 증가하였다. 그러나 $Cu^{2+}$제거효 율은 $Cu^{2+}$농도와 무관하게 거의 얼정한 값인 57% 를 보였다. $Zn^{2+}$제거량은 $Zn^{2+}$농도에 비례하나 증가율은 $Cu^{2+}$간에 비하여 매우 낮았다.