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標題: 高鹽甲烷太古生物分子伴護系統與壓力反應
Molecular Chaperone and Stress Response in Halophilic Methanogenic Archaea
作者: 賴美津
關鍵字: 太古生物;生物科學類;高鹽甲烷太古生物;分子伴護蛋白;化學伴護因子;壓力反應;基礎研究
隨著地球暖化的越趨明顯,氣候越來越極端,我們生存的環境也逐漸惡化,地球上生物需面對更嚴苛的極端生存考驗。了解古老生長在極端環境下的太古生物如何適應極端壓力的基因與策略並加以應用,應可幫助我們適應與存活。生物遭遇環境中溫度、壓力、酸鹼值、滲透壓、及氧化逆境時,細胞內的蛋白質構形可能改變或聚集而失去功能,普遍存在於細菌與真核生物中的分子伴護系統(Molecular chaperone),可協助矯正蛋白質的錯誤構形及拆開已形成的聚集蛋白,使蛋白恢復正確的構形及功能。因此分子伴護蛋白的演化與功能,對生物細胞在面對環境逆境的適應與存活機制上,扮演非常重要的角色。分子伴護蛋白系統在細菌與真核生物的探討非常多,但是在太古生物這方面的研究非常稀少。我們在探討高鹽甲烷太古生物對鹽逆境適應表現基因時,發現高鹽甲烷太古生物的分子伴護蛋白ClpB與GroEL/GroES基因,並證實這些基因會受鹽與溫度壓力誘導表現,且相容質betaine具有化學伴護因子功能會影響分子伴護蛋白的表現與活性。相容質betaine除了具有鹽與滲透壓保護因子的功能之外,對高低溫逆境亦有保護功能,且可以維持逆境下分子伴護蛋白的構形,與分子伴護蛋白共同作用可以提高變形蛋白恢復活性的比例,扮演化學伴護因子的功能。高鹽甲烷太古生物M. portucalensis FDF1具有betaine運輸與自體生合成特性,可做為探討細胞面對壓力時,分子伴護蛋白與化學伴護因子關係的模式生物。在此三年研究計畫其間,我們希望能藉由能運輸與自體生合成相容質betaine的高鹽甲烷太古生物,深入了解太古生物的分子伴護系統(ClpB/GroEL/GroES/DnaK/DnaJ/GrpE)的基因與蛋白特性、分子伴護系統對鹽與溫度逆境適應反應,及化學伴護因子betaine與分子伴護系統表現的競合關係。進一步希望能將高鹽太古生物的分子伴護系統的基因與蛋白,應用於細菌與原核生物,以協助這些生命對壓力的適應範圍更寬廣。

Molecular chaperones are ubiquitous and widely discussed in Bacteria and Eukarya. They assist proteins in achieving proper folding and reactivate the aggregated proteins damaged by stress. Archaea as Extremophiles are able to thrive in the harshest environmental conditions on this planet. And it is true that archaeal proteins are unique in remaining properly folded and functional under the extremes of salinity, temperature, and other adverse physical conditions that would normally lead to protein denaturation, loss of solubility, and aggregation. Although it was believed that molecular chaperones should be participated in the adaptation of archaeal cells to survive in the extreme environment, few and limited investigations has been initiated.We have identified and reported the first ClpB in Archaea while we investigated the differential salt stress expressed genes in halophilic methanogenic archaea- Methanohalo- philus portucalensis FDF1. We further demonstrated that ClpB/GroEL/GroES genes are cluster together and induced by temperature and salt stresses. M. portucalensis could transport and de no novo synthesize betaine as osmolyte to balance the osmotic pressure and protect cellular proteins while cell under salt and osmotic stresses. Our Northern experiments showed that, under salt and temperature stresses, the addition of betaine modulated the gene expression levels of molecular chaperone ClpB/GroEL/GroES which indicated glycine betaine may function as chemical chaperone to protect the proteins.In order to reveal the molecular chaperones system (ClpB/GroEL/GroES/DnaK/ DnaJ/GrpE) and its interplay with chemical chaperone under stress conditions. In this proposal, we plan to study all possible molecular chaperones in the betaine de novo synthesizing halophilic methanogen Methanohalophilus portucalensis FDF1. We will screen and analysis the genes and proteins function of ClpB/GroEL/GroES/DnaK/DnaJ/GrpE from M. portucalensis, study their chaperone function under salt, temperature and oxidative stresses and investigate the interplay between molecular chaperones and chemical chaperone betaine under each stress conditions. The knowledge in how do archaeal cells maintain their cellular function under extreme environmental challenge should benefit we human being a beamy light to fight for the global warming.
其他識別: NSC100-2311-B005-005
Appears in Collections:生命科學系所

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