大肠杆菌的IspH蛋白:研究铁硫集群的实施和催化
Tobias Gräwert1, Johannes Kaiser, Ferdinand Zepeck
1Contribution from the Lehrstuhl für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
Journal of the American Chemical Society
|October 8, 2004
概括
过度表达铁硫集群基因显著提高了大肠杆菌IspH酶活性,这对于异类生物合成至关重要. 这种增强需要特定的黄素度,并揭示了IspH蛋白内关键的 [3Fe-4S](+) 集群.
科学领域:
- 生物化学 生物化学
- 分子生物学分子生物学
- 微生物学 微生物学
背景情况:
- 非甲酸途径对于许多生物体的异烯酸生物合成至关重要,包括大肠杆菌.
- 该IspH酶催化了这一途径的关键步骤,将1-基-2-甲基-2-E-丁二酸转化为异丁二酸 (IPP) 和二甲基酸二酸 (DMAPP).
研究的目的:
- 为了增强来自大肠杆菌的IspH酶的催化活性.
- 调查铁硫集群和特定的半氨酸残留物在IspH功能中的作用.
主要方法:
- 在表达ispH.的工程大肠杆菌菌株中,isc操作子 (铁硫集群组件) 的过度表达.
- 对IspH蛋白进行无氧净化.
- 用不同度的黄素和黄素减少酶进行酶活性测定.
- 电子偏磁共振 (EPR) 谱学和光学吸收性用于描述铁硫团的特征.
- 保存的氨酸残留物的局部导向突变发生.
主要成果:
- 过度表达iscoperon增加了至少200倍的IspH催化活性.
- 需要的最大活性为40μM的黄素和12μM的黄素减少酶.
- EPR和光学吸收证实了IspH蛋白中的 [3Fe-4S](+) 集群.
- 任何三种保存的氨酸残留物 (在位置12,96和197) 的任何一种突变都大大降低了催化活性 (超过7万倍).
结论:
- 铁硫集群组装机械显著增强了IspH酶的活性.
- 由保存的氨酸残留物协调的A [3Fe-4S](+) 集群对于异烯酸生物合成中的IspH催化功能至关重要.
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