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首页> 外文期刊>Biochemistry >Spectroscopic and saturation magnetization properties of the manganese- and cobalt-substituted Fur (ferric uptake regulation) protein from Escherichia coli.
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Spectroscopic and saturation magnetization properties of the manganese- and cobalt-substituted Fur (ferric uptake regulation) protein from Escherichia coli.

机译：大肠杆菌中被锰和钴取代的Fur（铁吸收调节）蛋白的光谱和饱和磁化特性。

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摘要

The Fur apoprotein has been purified and reconstituted with Co2+ and Mn2+ ions. These samples have been analyzed by UV-visible, EPR, and 1H NMR spectroscopies, by XAS, and by magnetization measurements. The apo-Fur protein is able to bind one metal dication (Co2+ or Mn2+) per monomer. A saturation magnetization study confirms the presence of a high-spin metal dication [Mn(II) S = 5/2 and Co(II) S = 3/2]. The two metal ions per Fur dimer are not in magnetic interaction (J < 0.1 cm-1 ). The UV-visible spectrum of the cobalt-substituted form (Co-Fur) presents two main bands at 660 nm and 540(br) nm with epsilon540 nm = 65 M-1 cm-1. The EPR spectrum gives the following g values: gx = 5.0(5), gy = 4.0(2), and gz = 2. 3(1), which are in accordance with a nearly axial (E/D < 0.11) site. The value of 55 cm-1 for the splitting (Delta) between the ground and the first excited state has been derived from an EPR saturation study and is in agreement with magnetization data. The EXAFS data of Co-Fur indicate a metal environment comprising five nitrogen/oxygen atoms at 2.11 A, the absence of sulfur, and the presence of histidines as ligands. 1H NMR of Co-Fur in H2O and D2O shows at least two exchangeable signals coming from histidine NH protons and shows the signature of carboxylate group(s). The combined spectroscopic data allow us to propose that the main metal site of Fur in Co-Fur contains at least two histidines, at least one aspartate or glutamate, and no cysteine as ligands and is in an axially distorted octahedral environment.
机译：毛脱辅基蛋白已经纯化，并用Co2 +和Mn2 +离子重建。这些样品已通过UV-可见光，EPR和1H NMR光谱，XAS和磁化测量进行了分析。载脂蛋白-Fur蛋白能够与每个单体结合一种金属离子（Co2 +或Mn2 +）。饱和磁化强度研究证实了高自旋金属指示剂的存在[Mn（II）S = 5/2和Co（II）S = 3/2]。每个Fur二聚体中的两个金属离子没有磁性相互作用（J <0.1 cm-1）。钴取代形式（Co-Fur）的紫外-可见光谱在660 nm和540（br）nm处出现两个主要谱带，ε540 nm = 65 M-1 cm-1。 EPR光谱给出以下g值：gx = 5.0（5），gy = 4.0（2）和gz =2。3（1），它们符合近乎轴向（E / D <0.11）的位置。从EPR饱和度研究得出了地面与第一激发态之间的分裂（Δ）的55 cm-1值，该值与磁化数据一致。 Co-Fur的EXAFS数据表明，金属环境包含2.11 A处的五个氮/氧原子，不存在硫和存在作为配体的组氨酸。 Co-Fur在H2O和D2O中的1H NMR显示至少两个来自组氨酸NH质子的可交换信号，并显示一个或多个羧酸根基团的签名。合并的光谱数据允许我们提出，Co-Fur中Fur的主要金属位点包含至少两个组氨酸，至少一个天冬氨酸或谷氨酸，并且没有半胱氨酸作为配体，并且处于轴向扭曲的八面体环境中。

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