来自大肠杆菌的细胞染色体bd-I中的质子转移涉及CydBB中的Asp-105
M Janczak1, J Vilhjálmsdóttir1, P Ädelroth1
1Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
Biochimica et biophysica acta. Bioenergetics
|July 15, 2024
概括
细菌细胞染色体bd氧化酶对于病原体的生存至关重要. 这项研究揭示了一种依赖pH值的质子转移机制,与CydB子单元中的特定残留物有关,这对于氧气减少至关重要.
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:
- 细胞染色体bd氧化酶是必要的细菌末端氧化酶,特别是在低氧条件下.
- 这些酶对于许多病原体的生存至关重要,使它们成为潜在的抗菌药物点.
- 最大的子单元CydA含有三个关键的氧化还原因子:血红素b558,血红素b595和活性部位血红素d.
研究的目的:
- 调查大肠杆菌细胞染色体bd-I.中的氧 (O2) 减少机制.
- 阐明催化循环期间质子转移的动力学和途径.
- 确定特定子单位和残留物在质子转移中的作用.
主要方法:
- 利用流闪技术研究快速的酶反应.
- 采用位点定向突变发生法来改变CydB子单元中的特定氨基酸残留物.
- 分析过氧化物 (P) 到铁 (F) 过渡的pH依赖性动力学.
主要成果:
- F过渡速率是pH依赖的,最大活性在10^4s^-1左右,在pH较高时下降.
- 这种pH的依赖性表明,通过从pKa大约为9.7.7的残留物中的内部质子转移来限制速率.
- 在CydB中Asp58B和Asp105B的突变发生显著影响了催化周转,使它们参与了质子转移. 具体来说,Asp105B对于PF过渡至关重要.
结论:
- 涉及CydB的特定质子转移途径,特别是Asp105B,对于大肠杆菌细胞染色体bd-I的功能至关重要.
- 该研究确定了参与质子转移的高pKa残留物,并讨论了其在cytochrome bd超级家族中的保存.
- 了解这种机制可以了解细菌呼吸和抗菌药物开发的潜在目标.
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