在克雷白氏菌中，AcoK是調控aco基因群的轉錄因子。AcoK屬於LuxR家族中結合ATP的大調控因子群，且與MalT蛋白質具高度相似性。為進一步了解AcoK作用原理，我們建立了acoABCD或acoK基因啟動區與luxAB基因的報導系統並量測其表現。acoABCD基因啟動區的活性在對數生長期時非常低，並在早期靜止期才又回升。被認定為誘導物的乙醯甲基甲醇可刺激啟動區的表現，而葡萄糖則表現抑制現象。相反的，AcoK蛋白質對本身的基因並不具有自我調控能力。其他的乙醯甲基甲醇代謝物如2, 3-丁二醇與乙醛，以及其他糖類包括半乳糖，乳糖和甘油對acoABCD及acoK啟動區的表現能力並無明顯影響，而在210分鐘時，麥芽糖則可刺激acoK啟動區的表現。此外，啟動區的活性在鹼性pH值時會增加。在這些調控區的分析中，我們也找到一些區域與調控acoK及acoABCD基因表現有關的區域。為了解AcoK的功能，採用了針對特定區域與截型的突變方法。其中第一結合ATP結構區對活化acoABCD啟動區是必須的。同時，這活化機制也需要位於第416位置的天門冬胺酸(Asp)。總結來說，我們在此研究中測試了許多包括乙醯甲基甲醇，葡萄糖，乳糖，與pH值等影響acoABCD與acoK基因啟動區的因子及AcoK蛋白質結構區的作用，這些結果明顯增進我們對乙醯甲基甲醇基因的轉錄機制的了解。

AcoK is a transcription regulator of aco operon in Klebsiella pneumoniae. It belongs to large ATP binding regulators of the LuxR family and shows high homology with MalT. In order to understand how AcoK regulates its target genes, the promoter region of either acoABCD or acoK was fused with the reporter gene luxAB and its expression was measured. The activity of Paco was very low during logarithmic growth and it started to increase after entering early stationary phase. Acetoin was shown to function as an inducer for the expression of aco genes, whereas glucose exhibited a repression effect. The result is in contrast to the expression of acoK, which is not autoregulated. The catabolites of acetoin metabolism such as 2,3-butanediol and acetaldehyde as well as other carbohydrates including galactose, lactose, and glycerol did not affect the expression of Paco and PacoK, whereas maltose stimulates the expression of PacoK at 210 min. The activity of Paco appeared to be high at alkaline pH0. Regions required for the function of Paco and PacoK were also identified. Finally, site-directed mutagenesis and deletion analysis were performed to investigate the function of AcoK. The ATP-binding domain I was shown to be essential for the ability of AcoK to activate Paco. The Asp residue located at 416th amino acid was also found to be critical for Paco activity. In conclusion, we have identified several factors that affect Paco and PacoK, and domains in AcoK that are critical for its activity. The result provides important insight on the transcription mechanism of aco genes.

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