电子推进:改变Lactococcus lactis中二氧化酸脱酶1B中电子的催化分布的变体
Corine O Smith1, Richa Khatiwada1, Pengfei Li1
1Loyola University Chicago, Department of Chemistry and Biochemistry, 1068 W Sheridan Rd, Chicago, Illinois 60660, United States.
氨酸脱酶1B (DHOD1B) 酶使用黄素辅因子进行电子转移. 变体揭示了影响Lactococcus lactis DHOD1B电子分布和催化活性的关键残留物.
科学领域:
- 生物化学 生化学
- 酶学 是一种酶学.
- 蛋白质科学 蛋白质科学
背景情况:
- 双酸脱酶1B (DHOD1B) 是一种利用与黄素辅因子 (FAD和FMN) 有活性半位点的黄蛋白.
- 半位点之间的电子转移至关重要,并由铁硫中心介导.
- 乳球球菌乳糖DHOD1B (LlDHOD1B) 呈现一种内部电子分布平衡,涉及flavin bisemiquinone状态.
研究的目的:
- 调查LllDHOD1B.内部电子传输通路中的特定残留物的作用.
- 阐明关键氨基酸对弗拉辅因子功能的静电和催化作用.
- 了解基质结合如何影响辅助因子的氧化还原特性.
主要方法:
- 用局部定向的突变生成来创建LllDHOD1B (K48M,E221Q,C135A) 的变种形式.
- 使用光谱和电化学方法分析了黄素状态和氧化还原潜力.
- 测量了酶动力学以评估催化活性和基质减少率.
主要成果:
- 该K48M变体显示,阳离子半氨酸位于FMN,而lysine 48对FMN的pKa和降解潜力产生静电影响.
- E221Q变体证明了Glutamate 221在调节NADH化物转移和酸盐减少率方面的作用,减少了比塞米农的积累.
- 该C135A变种阻断了酸盐的降解,使得在酸盐结合时FMN降解潜力的+70 mV转移能够确定.
结论:
- 特定的残留物,如氨酸48,氨酸221和氨酸135,在LllDHOD1B的电子转移机制和催化效率中发挥着关键作用.
- 静电相互作用和接近弗拉辅因子是弗拉氧化还原特性和酶活性的关键决定因素.
- 了解这些机制可以了解黄蛋白功能和潜在的治疗点.
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