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Published on: December 18, 2010
在细胞染色体c6家族中调节血红素还原潜力
Jonathan A R Worrall1, Beatrix G Schlarb-Ridley, Torsten Reda
1Department of Biochemistry, University of Cambridge, Cambridge, UK. jw510@mole.bio.cam.ac.uk
Journal of the American Chemical Society
|July 13, 2007
概括
细胞染色体c6A,与细胞染色体c6不同,由于Val残留物,具有较低的血中点潜力. 这种差异可能促进了细胞染色体c6A在光合作用中的独特功能的演变.
科学领域:
- 生物化学 生物化学
- 光合作用研究研究光合作用.
- 蛋白质结构-功能分析
背景情况:
- 细胞染色体c6A是一种在绿藻和植物中发现的独特的ditio-cytochrome.
- 它与细胞染色体c6具有结构上的相似性,但在光系统I中不能执行相同的电子传递功能.
- 细胞染色体c6A的血红中点潜力明显低于细胞染色体c6.
研究的目的:
- 与细胞染色体c6.6.相比,研究细胞染色体c6A中低血中点潜力的分子基础.
- 了解细胞染色体c6A和细胞染色体c6.6之间的进化差异.
主要方法:
- 使用X射线晶体学来确定Phormidium laminosum中的cytochromec6的结构,并将其与cytochromec6A进行比较.
- 蛋白膜电压测量用于测量野生类型和突变蛋白质的血中点潜力.
- 结构分析的重点是血红素口袋的差异,特别是Gln51 (细胞色素c6) 和Val52 (细胞色素c6A) 的残留物.
主要成果:
- 发现的一个关键差异是,在细胞染色体c6中,用细胞染色体c6A中的Val取代了保存的Gln残留物.
- 这些残留物的交换显著改变了血红素中点潜力:c6A (V52Q突变) 的+109mV和c6 (Q51V突变) 的-100mV.
- V52Q突变体的X射线结晶学显示,Gln残留物采用了一种使氧化血形式不稳定的配置.
结论:
- 在血口袋中用Val替换Gln被提出为一个关键的进化步骤,推动了细胞染色体c6A的功能分歧.
- 这种氨基酸变化降低了血红素中点潜力,可能会抑制细胞染色体b6f复合体的减少.
- 这种改变的潜能有助于在光合作用生物中为细胞染色体c6A建立新的,独特的功能.
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