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首页> 外文期刊>The FEBS journal >Role of the surface charges D72 and K8 in the function and structural stability of the cytochrome c(6) from Nostoc sp PCC 7119
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Role of the surface charges D72 and K8 in the function and structural stability of the cytochrome c(6) from Nostoc sp PCC 7119

机译：表面电荷D72和K8在Nostoc sp PCC 7119的细胞色素c（6）的功能和结构稳定性中的作用

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摘要

We investigated the role of electrostatic charges at positions D72 and K8 in the function and structural stability of cytochrome c(6) from Nostoc sp. PCC 7119 (cyt c(6)). A series of mutant forms was generated to span the possible combinations of charge neutralization (by mutation to alanine) and charge inversion (by mutation to lysine and aspartate, respectively) in these positions. All forms of cyt c(6) were functionally characterized by laser flash absorption spectroscopy, and their stability was probed by urea-induced folding equilibrium relaxation experiments and differential scanning calorimetry. Neutralization or inversion of the positive charge at position K8 reduced the efficiency of electron transfer to photosystem I. This effect could not be reversed by compensating for the change in global charge that had been introduced by the mutation, indicating a specific role for K8 in the formation of the electron transfer complex between cyt c(6) and photosystem I. Replacement of D72 by asparagine or lysine increased the efficiency of electron transfer to photosystem I, but destabilized the protein. D72 apparently participates in electrostatic interactions that stabilize the structure of cyt c(6). The destabilizing effect was reduced when aspartate was replaced by the small amino acid alanine. Complementing the mutation D72A with a charge neutralization or inversion at position K8 led to mutant forms of cyt c(6) that were more stable than the wild-type under all tested conditions.
机译：我们调查了静电荷在位置D72和K8在功能和结构稳定性的细胞色素c（6）来自Nostoc sp的作用。 PCC 7119（cyt c（6））。生成了一系列突变形式，以涵盖这些位置中电荷中和（通过突变为丙氨酸）和电荷反转（分别通过突变为赖氨酸和天冬氨酸）的可能组合。 cyt c（6）的所有形式均通过激光闪光吸收光谱法进行了功能表征，并通过尿素诱导的折叠平衡弛豫实验和差示扫描量热法探讨了其稳定性。 K8位置正电荷的中和或反转会降低电子转移至光系统I的效率。无法通过补偿突变引起的整体电荷变化来抵消这种影响，这表明K8在K8分子中的特定作用。 cyt c（6）与光系统I之间的电子转移复合物的形成。用天冬酰胺或赖氨酸替代D72可提高电子转移至光系统I的效率，但会使蛋白质不稳定。 D72显然参与静电相互作用，稳定了cyt c（6）的结构。当天冬氨酸被小氨基酸丙氨酸代替时，去稳定作用降低。在位置K8处通过电荷中和或反转来补充突变D72A，导致在所有测试条件下均比野生型更稳定的cyt c（6）突变形式。

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