...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >Fourier Transform Infrared Detection of a Polarizable Proton Trapped between Photooxidized Tyrosine YZ and a Coupled Histidine in Photosystem II: Relevance to the Proton Transfer Mechanism of Water Oxidation
【24h】

Fourier Transform Infrared Detection of a Polarizable Proton Trapped between Photooxidized Tyrosine YZ and a Coupled Histidine in Photosystem II: Relevance to the Proton Transfer Mechanism of Water Oxidation

机译：光系统中光氧化酪氨酸YZ和组氨酸偶合之间极化的质子的傅里叶变换红外检测II：与水氧化质子转移机制的相关性

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The redox-active tyrosine YZ (D1-Tyr161) in photosystem II (PSII) functions as an immediate electron acceptor of the Mn_4Ca cluster, which is the catalytic center of photosynthetic water oxidation. YZ is also located in the hydrogen bond network that connects the Mn_4Ca cluster to the lumen and hence is possibly related to the proton transfer process during water oxidation. To understand the role of YZ in the water oxidation mechanism, we have studied the hydrogen bonding interactions of YZ and its photooxidized neutral radical Y_Z~? together with the interaction of the coupled His residue, D1-His190, using light-induced Fourier transform infrared (FTIR) difference spectroscopy. The Y_Z~?-minus-YZ FTIR difference spectrum of Mn-depleted PSII core complexes exhibited a broad positive feature around 2800 cm~(?1), which was absent in the corresponding spectrum of another redox-active tyrosine YD (D2-Tyr160). Analyses by 15N and H/D substitutions, examination of the pH dependence, and density functional theory and quantum mechanics/molecular mechanics (QM/MM) calculations showed that this band arises from the N?H stretching vibration of the protonated cation of D1-His190 forming a charge-assisted strong hydrogen bond with Y_Z~?. This result provides strong evidence that the proton released from YZ upon its oxidation is trapped in D1-His190 and a positive charge remains on this His. The broad feature of the ～2800 cm~(?1) band reflects a large proton polarizability in the hydrogen bond between Y_Z~? and HisH~+. QM/MM calculations further showed that upon YZ oxidation the hydrogen bond network is rearranged and one water molecule moves toward D1-His190. From these data, a novel proton transfer mechanism via Y_Z~?-HisH~+ is proposed, in which hopping of the polarizable proton of HisH~+ to this water triggers the transfer of the proton from substrate water to the luminal side. This proton transfer mechanism could be functional in the S_2 → S_3 transition, which requires proton release before electron transfer because of an excess positive charge on the Mn_4Ca cluster.
机译：光系统II（PSII）中具有氧化还原活性的酪氨酸YZ（D1-Tyr161）充当Mn_4Ca团簇的直接电子受体，Mn_4Ca团簇是光合水氧化的催化中心。 YZ也位于将Mn_4Ca团簇连接至内腔的氢键网络中，因此可能与水氧化过程中的质子转移过程有关。为了了解YZ在水氧化机理中的作用，我们研究了YZ及其光氧化的中性自由基Y_Z〜？的氢键相互作用。以及使用光诱导傅立叶变换红外（FTIR）差光谱技术分析偶联的His残基D1-His190的相互作用。 Mn耗尽的PSII核配合物的Y_Z〜？-YZ FTIR差异光谱在2800 cm〜（？1）附近表现出宽广的正特征，而另一种氧化还原活性酪氨酸YD（D2-Tyr160 ）。通过15N和H / D取代，对pH依赖性的检查以及密度泛函理论和量子力学/分子力学（QM / MM）计算的分析表明，该谱带是由D1-质子化阳离子的N？H拉伸振动引起的His190与Y_Z〜？形成电荷辅助的强氢键。该结果提供了有力的证据，证明了从YZ释放出来的质子在氧化后被困在D1-His190中，并且在此His上保留了正电荷。 〜2800 cm〜（？1）谱带的宽广特征反映了Y_Z〜？之间的氢键中质子极化性强。和HisH〜+。 QM / MM计算进一步表明，YZ氧化后，氢键网络重新排列，一个水分子向D1-His190移动。根据这些数据，提出了一种经由Y_Z〜β-HisH〜+的新型质子转移机制，其中，HisH〜+的极化质子向该水的跃迁触发了质子从底物水向腔内侧的转移。这种质子传递机制可能在S_2→S_3跃迁中起作用，由于Mn_4Ca团簇上的正电荷过多，因此需要在电子传递之前释放质子。

著录项

相似文献

  • 外文文献
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