...
首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Thermodynamic equilibrium between blue and green copper sites and the role of the protein in controlling function
【24h】

Thermodynamic equilibrium between blue and green copper sites and the role of the protein in controlling function

机译:蓝色和绿色铜位点之间的热力学平衡以及蛋白质在控制功能中的作用

获取原文
获取原文并翻译 | 示例
           

摘要

A combination of spectroscopies and density functional theory calculations indicate that there are large temperature-dependent absorption spectral changes present in green nitrite reductases (NiRs) due to a thermodynamic equilibrium between a green and a blue type 1 (T1) copper site. The axial methionine (Met) ligand is unconstrained in the oxidized NiRs, which results in an enthalpi-cally favored (△H≈ 4.6 kcal/mol) Met-bound green copper site at low temperatures, and an entropically favored (T△S≈ 4.5 kcal/mol, at room temperature) Met-elongated blue copper site at elevated temperatures. In contrast to the NiRs, the classic blue copper sites in plastocyanin and azurin show no temperature-dependent behavior, indicating that a single species is present at all temperatures. For these blue copper proteins, the polypeptide matrix opposes the gain in entropy that would be associated with the loss of the weak axial Met ligand at physiological temperatures by constraining its coordination to copper. The potential energy surfaces of Met binding indicate that it stabilizes the oxidized state more than the reduced state. This provides a mechanism to tune down the reduction potential of blue copper sites by >200 mV.
机译:光谱学和密度泛函理论计算的结合表明,由于绿色和蓝色1型(T1)铜位点之间的热力学平衡,绿色亚硝酸盐还原酶(NiRs)中存在依赖于温度的大吸收光谱变化。轴向甲硫氨酸(Met)配体在氧化的NiRs中不受约束,这导致在低温下产生焓受青睐的(△H≈4.6 kcal / mol)Met结合的绿铜位点,并得到受熵青睐的(T△S≈室温下为4.5 kcal / mol)在升高的温度下会被拉长的蓝铜。与NiR相比,质蓝蛋白和天青蛋白中的经典蓝铜位点没有温度依赖性,这表明在所有温度下都存在单个物种。对于这些蓝色的铜蛋白,多肽基质通过限制其与铜的配位而反对熵的增加,而熵的增加与生理温度下弱轴向Met配体的损失有关。 Met结合的势能表面表明它比还原态更稳定氧化态。这提供了一种将蓝铜位的还原电位调低> 200 mV的机制。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号