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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Manganese and cobalt binding in a multi-histidinic fragment
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Manganese and cobalt binding in a multi-histidinic fragment

机译：多组织片段中的锰和钴结合

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摘要

The binding of Mn(ii) and Co(ii) ions to a multi-histidinic peptide, the three repeats (T_1R_2S_3R_4S_5H_6T_7S_8E_9G_(10))_3 portion of Cap43 protein, has been studied. Potentiometric measurements have been used to investigate the protonation equilibria and stoichiometry of the species obtained in a wide range of pH and at a 1:1 ligand-to-metal molar ratio. NMR, UV-visible and EPR spectroscopy techniques have been used to investigate the role of multi-histidinic and glutamate sites in coordinating metal ions. ~1H-~1H TOCSY, ~1H-~(13)C HSQC multidimensional NMR techniques were performed to understand the details of metal binding sites and the conformational behaviour of the peptide. The effects of the peptide titration with the two metals have been followed by paramagnetic selective line-broadening in the 1D NMR spectra and the signals' disappearance in the 2D ~1H-~(13)C HSQC and ~1H-~1H TOCSY. Both ions showed common binding donor atoms: the main manganese and cobalt binding centre of the peptide fragment is associated with histidine and glutamate residues. The specific perturbation of NMR resonances indicated that the coordination involves imidazole N_ε of histidine and carboxyl γ-O of glutamate residue. All the three imidazole N_ε of His_6, His_(16) and His_(26), as well as carboxyl γ-O of Glu_9, Glu_(19) and Glu_(29), in an octahedral arrangement are involved in the coordination in the physiological pH range. The involvement of hydroxyl γ-O from the threonine (or serine) side chain can also be observed. Manganese and cobalt complexation induces important structural changes within the C-terminal portion of the ligand, constraining it to leave its disordered conformation. A model of the structure of manganese and cobalt species can be obtained from our data.
机译：已经研究了Cap43蛋白的三个重复序列（T_1R_2S_3R_4S_5H_6T_7S_8E_9G_（10））_ 3部分中的Mn（ii）和Co（ii）离子与多组蛋白肽的结合。电位测量已用于研究在宽pH范围和1：1配体与金属的摩尔比下获得的物质的质子平衡和化学计量。 NMR，UV可见光谱和EPR光谱技术已用于研究多组氨酸和谷氨酸位点在配位金属离子中的作用。进行了〜1H-〜1H TOCSY，〜1H-〜（13）C HSQC多维NMR技术，以了解金属结合位点的详细信息和肽的构象行为。在用两种金属进行肽滴定后，在1D NMR谱中顺磁性选择性线扩大，在2D〜1H-〜（13）C HSQC和〜1H-〜1H TOCSY中信号消失。两种离子均显示出共同的结合供体原子：肽片段的主要锰和钴结合中心与组氨酸和谷氨酸残基相关。 NMR共振的特定扰动表明配位涉及组氨酸的咪唑N_ε和谷氨酸残基的羧基γ-O。 His_6，His_（16）和His_（26）的所有三个咪唑N_ε以及Glu_9，Glu_（19）和Glu_（29）的羧基γ-O都参与八面体排列pH范围。还可以观察到苏氨酸（或丝氨酸）侧链中羟基γ-O的参与。锰和钴的络合会在配体的C端部分引起重要的结构变化，从而使其离开无序构象。锰和钴物种的结构模型可以从我们的数据中获得。

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