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Selective metal binding by Vanabin2 from the vanadium-rich ascidian, Ascidia sydneiensis samea

机译:Vanabin2对富钒海鞘沙地黄沙门氏菌的选择性金属结合

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Vanadium-binding proteins, or Vanabins, have recently been isolated from the vanadium-rich ascidian, Ascidia sydneiensis samea. Recent reports indicate that Vanabin2 binds twenty V(IV) ions at pH 7.5, and that it has a novel bow-shaped conformation. However, the role of Vanabin2 in vanadium accumulation by the ascidian has not yet been determined. In the present study, the effects of acidic pH on selective metal binding to Vanabin2 and on the secondary structure of Vanabin2 were examined. Vanabin2 selectively bound to V(IV), Fe(III), and Cu(II) ions under acidic conditions. In contrast, Co(II), Ni(II), and Zn(II) ions were bound at pH 6.5 but not at pH 4.5. Changes in pH had no detectable effect on the secondary structure of Vanabin2 under acidic conditions, as determined by circular dichroism spectroscopy, and little variation in the dissociation constant for V(IV) ions was observed in the pH range 4.5-7.5, suggesting that the binding state of the ligands is not affected by acidification. Taken together, these results suggest that the reason for metal ion dissociation upon acidification is attributable not to a change in secondary structure but, rather, that it is caused by protonation of the amino acid ligands that complex with V(IV) ions. (c) 2006 Elsevier B.V. All rights reserved.
机译:钒结合蛋白或Vanabins,最近已从富含钒的海藻sydneiensis samea中分离出来。最近的报道表明,Vanabin2在pH 7.5时结合二十个V(IV)离子,并且它具有新颖的弓形构象。但是,尚未确定Vanabin2在海藻中钒积累中的作用。在本研究中,研究了酸性pH对选择性金属与Vanabin2结合以及Vanabin2二级结构的影响。 Vanabin2在酸性条件下选择性结合V(IV),Fe(III)和Cu(II)离子。相反,Co(II),Ni(II)和Zn(II)离子在pH 6.5而不是pH 4.5结合。 pH值的变化对酸性条件下Vanabin2的二级结构没有可检测到的影响(通过圆二色光谱法测定),并且在4.5-7.5的pH范围内,V(IV)离子的离解常数几乎没有变化,这表明配体的结合状态不受酸化的影响。综上所述,这些结果表明,酸化时金属离子解离的原因并非归因于二级结构的改变,而是归因于与V(IV)离子络合的氨基酸配体的质子化。 (c)2006 Elsevier B.V.保留所有权利。

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