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首页> 外文期刊>Biochemistry >Autoreduction of Ferryl Myoglobin: Discrimination among the Three Tyrosine and Two Tryptophan Residues as Electron Donors.
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Autoreduction of Ferryl Myoglobin: Discrimination among the Three Tyrosine and Two Tryptophan Residues as Electron Donors.

机译：Ferryl肌红蛋白的自动还原：区分三个酪氨酸和两个色氨酸残基作为电子供体。

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摘要

Ferric myoglobin undergoes a two-electron oxidation in its reaction with H(2)O(2). One oxidation equivalent is used to oxidize Fe(III) to the Fe(IV) ferryl species, while the second is associated with a protein radical but is rapidly dissipated. The ferryl species is then slowly reduced back to the ferric state by unknown mechanisms. To clarify this process, the formation and stability of the ferryl forms of the Tyr --> Phe and Trp --> Phe mutants of recombinant sperm whale myoglobin (SwMb) were investigated. Kinetic studies showed that all the mutants react normally with H(2)O(2) to give the ferryl species. However, the rapid phase of ferryl autoreduction typical of wild-type SwMb was absent in the triple Tyr --> Phe mutant and considerably reduced in the Y103F and Y151F mutants, strongly implicating these two residues as intramolecular electron donors. Replacement of Tyr146, Trp7, or Trp14 did not significantly alter the autoreduction, indicating that these residues do not contribute to ferryl reduction despite the fact that Tyr146 is closer to the iron than Tyr151 or Tyr103. Furthermore, analysis of the fast phase of autoreduction in the dimer versus recovered monomer of the Tyr --> Phe mutant K102Q/Y103F/Y146F indicates that the Tyr151-Tyr151 cross-link is a particularly effective electron donor. The presence of an additional, slow phase of reduction in the triple Tyr --> Phe mutant indicates that alternative but normally minor electron-transfer pathways exist in SwMb. These results demonstrate that internal electron transfer is governed as much by the tyrosine pK(a) and oxidation potential as by its distance from the electron accepting iron atom.
机译：铁肌红蛋白在与H（2）O（2）的反应中经历两电子氧化。一种氧化当量用于将Fe（III）氧化为Fe（IV）的Ferryl物种，而另一种则与蛋白质自由基结合，但会迅速消散。然后，通过未知机制，将ferryl物种缓慢还原成三价铁态。为了阐明这一过程，研究了重组抹香鲸肌红蛋白（SwMb）的Tyr-> Phe和Trp-> Phe突变体的ferryl形式的形成和稳定性。动力学研究表明，所有的突变体都可以正常地与H（2）O（2）反应，从而生成ferryl。但是，野生型SwMb典型的Ferryl自动还原的快速阶段在三重Tyr-> Phe突变体中不存在，而在Y103F和Y151F突变体中则大大减少，这强烈暗示了这两个残基为分子内电子供体。替换Tyr146，Trp7或Trp14不会显着改变自还原反应，这表明尽管Tyr146比Tyr151或Tyr103更接近铁，但这些残基也无助于降低小环。此外，对Tyr-> Phe突变体K102Q / Y103F / Y146F的二聚体相对于回收的单体的自动还原快速相的分析表明，Tyr151-Tyr151交联是一种特别有效的电子供体。在三重Tyr-> Phe突变体中还存在一个缓慢的还原相，这表明SwMb中存在替代但通常较小的电子转移途径。这些结果表明内部电子转移受酪氨酸pK（a）和氧化电势的影响与其与电子接受铁原子的距离一样多。

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