Journal of Life Science (생명과학회지)

Korean Society of Life Science (한국생명과학회)
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Heterologous Expression of Fission Yeast Heavy Metal Transporter, SpHMT-1, Confer Tolerance to Cadmium in Cytosolic Phytochelatin-Deficient Saccharomyces cerevisiae

분열효모 SpHMT1을 세포질 파이토킬레이트를 생성하지 않는 효모에서 발현으로 인한 카드뮴에 대한 저항성 증가

  • Lee, Sang-Man (Division of Applied Biology and Chemistry, School of Applied Biosciences, College of Agriculture and Life Sciences, Kyungpook National University)
  • 이상만 (경북대학교 응용생명과학부)
  • Published : 2009.12.30
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Abstract

Phytochelatins (PCs) are small polypeptides synthesized by PC synthase (PCS). They are present in various living organisms including plants, fission yeast, and some animals. The presumed function of PCs is the sequestration of cytosolic toxic heavy metals like cadmium (Cd) into the vacuoles via vacuolar membrane localized heavy metal tolerance factor 1 (HMT-1). HMT-1 was first identified in fission yeast (SpHMT-1), and later in Caenorhabdtis (CeHMT-1). Recently, its homolog has also been found in PC-deficient Drosophila (DmHMT-1), and this homolog has been shown to be involved in Cd detoxification, as confirmed by the heterologous expression of DmHMT-1 in fission yeast. Therefore, the dependence of HMT-1 on PC in Cd detoxification should be re-evaluated. I heterologously expressed SpHMT-1 in cytosolic PC-deficient yeast, Saccharomycea cerevisiae, to understand the dependence of HMT-1 on PC. Yeast cells expressing SpHMT-1 showed increased tolerance to Cd compared with control cells. This result indicates that SpHMT-1 is not strictly correlated with PC production on its function. Moreover, yeast cells expressing SpHMT-1 showed increased tolerance to exogenously applied glutathione (GSH) compared with control cells, and the tolerance to Cd was further increased by exogenously applied GSH, while tolerance in control cells was not. These results indicate that the function of SpHMT-1 in Cd detoxification does not depend on PCs only, and suggest that SpHMT-1 may sequester cytosolic GSH-Cd complexes into the vacuole.

파이토킬레이트(PC)는 PCS에 의해 생성되는 작은 폴리펩타이드로서 여러 생물에서 발견되고 있다. PC의 역할은 카드뮴과 같은 중금속을 세포질에서 결합하며 이는 액포막에 존재하는 HMT에 의해서 액포 안으로 이동된다. HMT1은 분열효모에서 처음으로 알려졌으며 이후 선충, 초파리 등에서도 발견되었으며 세포 내 역할은 카드뮴 같은 중금속 해독에 관여를 하고 있다. 하지만 액포가 존재하지 않고 PC를 생성하지 않는 초파리에서의 HMT1의 발견은 그 동안 알려진 HMT1의 역할을 재 조명하게 된다. 따라서 PC를 생성하지 못하는 출아효모에 PC를 생성하는 분열효모 유래 SpHMT1을 발현시켜 카드뮴에 대한 저항성을 분석하였다. SpHMT1을 발현하는 출아효모는 카드뮴에 대한 저항성이 현저하게 증가되었고 이는 SpHMT1이 PC가 존재하지 않는 조건에서도 카드뮴에 대한 해독작용을 하는 것을 암시한다. 또한 SpHMT1을 발현하는 출아효모는 GSH에 대한 저항성을 보였고 카드뮴에 대한 저항성도 GHS에 의해서 더 증가되는 결과를 보였다. 이러한 결과는 HMT1이 PC와 결합된 카드뮴을 액포안으로 이동시키는 가능성보다 GSH와 결합된 카드뮴을 액포 안으로 이동시켜 카드뮴에 대한 해독작용을 한다는 것을 암시한다.

Keywords

References

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