Kβ Valence to Core X-ray Emission Studies of Cu(I) Binding Proteins with Mixed Methionine - Histidine Coordination. Relevance to the Reactivity of the M- and H-sites of Peptidylglycine Monooxygenase.
Kβ Valence to Core X-ray Emission Studies of Cu(I) Binding Proteins with Mixed Methionine - Histidine Coordination. Relevance to the Reactivity of the M- and H-sites of Peptidylglycine Monooxygenase.
复制标题
Kβ 价与混合蛋氨酸-组氨酸协调的 Cu(I) 结合蛋白的核心 X 射线发射研究。
DOI：
10.1021/acs.inorgchem.5b02842
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发表时间：
2016
影响因子：
4.6
通讯作者：
Blackburn,NinianJ
中科院分区：
文献类型：
--
作者：
Martin-Diaconescu,Vlad;Chacón,KellyN;Delgado-Jaime,MarioUlises;Sokaras,Dimosthenis;Weng,Tsu-Chien;DeBeer,Serena;Blackburn,NinianJ
生物系统使用铜作为许多金属蛋白的氧化还原中心，其中金属的作用是在其+1和+2氧化态之间循环。这种化学需要氧化还原电位在可以稳定Cu（I）和Cu（II）状态的范围内，并且通常涉及蛋白质衍生的配体集合，其涉及混合的组氨酸-甲硫氨酸配位，其平衡两种氧化态的偏好。另一方面，转运蛋白利用Cu（I）状态的铜，并且通常含有主要由亲铜残基甲硫氨酸组成的位点。允许酶和转运蛋白平衡其氧化还原需求的电子因素是复杂的，并且由于缺乏Cu（I）状态的光谱探针而常常是难以捉摸的。在这里，我们提出了新的应用X-射线发射光谱铜蛋白通过一系列的混合His-Met铜位点的配体集之间的His 3和Met 3limits的变化，在一个系统的方式进行研究。这些位点来源于野生型肽基甘氨酸单加氧酶（PHM）、复制其两个铜位点（CuM-位点和CuH-位点）中的每一个的两个单位点变体以及转运蛋白CusF和CusB。在Met 3和His 3限度下，在Kβ2，5区观察到明显差异。CusB（Met 3）在8978.4 eV处具有明显的峰，在8975.6 eV处具有宽肩，而CuH（His 3）具有两个良好分辨的特征：在8974.8 eV处的更强特征和在8977.2 eV处的第二特征。混合配位球CusF（Met 2 His）和PHM CuM变体（Met 1His 2）具有非常相似的光谱，由8975.2和8977.8 eV的两个特征组成。DFT计算的光谱的分析表明，在8978 eV附近的较高的能量峰的强度介导的混合的配体为基础的轨道到Cu d10歧管，与S从Met提供更多的强度，通过促进增加Cu p-d混合。此外，WT PHM与CO（一种氧类似物）的反应产生了M位点CO络合物，其显示出独特的XES光谱，该光谱可以通过包括Cu（I）和CO配体之间的相互作用来计算再现。该研究表明，价核（VtC）区域不仅可以作为探针的配体形态，但也提供了深入了解的配位几何形状，以类似于XAS前边缘的方式，并可能是足够敏感的外源配体的配位是有用的反应机制的研究。
Biological systems use copper as a redox center in many metalloproteins, where the role of the metal is to cycle between its +1 and +2 oxidation states. This chemistry requires the redox potential to be in a range that can stabilize both Cu(I) and Cu(II) states and often involves protein-derived ligand sets involving mixed histidine–methionine coordination that balance the preferences of both oxidation states. Transport proteins, on the other hand, utilize copper in the Cu(I) state and often contain sites comprised predominately of the cuprophilic residue methionine. The electronic factors that allow enzymes and transporters to balance their redox requirements are complex and are often elusive due to the dearth of spectroscopic probes of the Cu(I) state. Here we present the novel application of X-ray emission spectroscopy to copper proteins via a study of a series of mixed His-Met copper sites where the ligand set varies in a systematic way between the His3and Met3limits. The sites are derived from the wild-type peptidylglycine monooxygenase (PHM), two single-site variants which replicate each of its two copper sites (CuM-site and CuH-site), and the transporters CusF and CusB. Clear differences are observed in the Kβ2,5region at the Met3and His3limits. CusB (Met3) has a distinct peak at 8978.4 eV with a broad shoulder at 8975.6 eV, whereas CuH(His3) has two well-resolved features: a more intense feature at 8974.8 eV and a second at 8977.2 eV. The mixed coordination sphere CusF (Met2His) and the PHM CuMvariant (Met1His2) have very similar spectra consisting of two features at 8975.2 and 8977.8 eV. An analysis of DFT calculated spectra indicate that the intensity of the higher energy peak near 8978 eV is mediated by mixing of ligand-based orbitals into the Cu d10manifold, with S from Met providing more intensity by facilitating increased Cu p–d mixing. Furthermore, reaction of WT PHM with CO (an oxygen analogue) produced the M site CO complex, which showed a unique XES spectrum that could be computationally reproduced by including interactions between Cu(I) and the CO ligand. The study suggests that the valence-to-core (VtC) region can not only serve as a probe of ligand speciation but also offer insight into the coordination geometry, in a fashion similar to XAS pre-edges, and may be sufficiently sensitive to the coordination of exogenous ligands to be useful in the study of reaction mechanisms.