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首页> 外文期刊>Biochemistry >Spectroscopic Definition of the Biferrous and Biferric Sites in de Novo Designed Four-Helix Bundle DFsc Peptides: Implications for O2 Reactivity of Binuclear Non-Heme Iron Enzymes
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Spectroscopic Definition of the Biferrous and Biferric Sites in de Novo Designed Four-Helix Bundle DFsc Peptides: Implications for O2 Reactivity of Binuclear Non-Heme Iron Enzymes

机译：de Novo设计的四螺旋束DFsc肽中的亚铁和双歧位点的光谱学定义：对双核非血红素铁酶的O2反应性的影响

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摘要

DFsc is a single chain de novo designed four-helix bundle peptide that mimics the core protein fold and primary ligand set of various binuclear non-heme iron enzymes. DFsc and the E11D, Y51L, and Y18F single amino acid variants have been studied using a combination of near-IR circular dichroism (CD), magnetic circular dichroism (MCD), variable temperature variable field MCD (VTVH MCD), and X-ray absorption (XAS) spectroscopies. The biferrous sites are all weakly antiferromagnetically coupled with μ-1,3 carboxylate bridges and one 4-coordinate and one 5-coordinate Fe, very similar to the active site of class I ribonucleotide reductase (R2) providing open coordination positions on both irons for dioxygen to bridge. From perturbations of the MCD and VTVH MCD the iron proximal to Y51 can be assigned as the 4-coordinate center, and XAS results show that Y51 is not bound to this iron in the reduced state. The two open coordination positions on one iron in the biferrous state would become occupied by dioxygen and Y51 along the O2 reaction coordinate. Subsequent binding of Y51 functions as an internal spectral probe of the O2 reaction and as a proton source that would promote loss of H2O2. Coordination by a ligand that functions as a proton source could be a structural mechanism used by natural binuclear iron enzymes to drive their reactions past peroxo biferric level intermediates.
机译：DFsc是单链从头设计的四螺旋束多肽，可模拟各种双核非血红素铁酶的核心蛋白折叠和主要配体组。已使用近红外圆二色性（CD），磁圆二色​​性（MCD），可变温度可变场MCD（VTVH MCD）和X射线的组合研究了DFsc和E11D，Y51L和Y18F单氨基酸变体吸收（XAS）光谱学。双亚铁位点均与μ-1,3羧酸盐桥和一个4位配位和1个5位配位的Fe进行弱反铁磁耦合，非常类似于I类核糖核苷酸还原酶（R2）的活性位点，在两个铁上均提供了开放的配位位置双氧桥。根据MCD和VTVH MCD的扰动，可以将Y51附近的铁指定为4坐标中心，并且XAS结果表明Y51在还原状态下未绑定到该铁。一氧化二铁状态下一个铁上的两个开放配位位置将沿着O2反应坐标被双氧和Y51占据。 Y51的后续结合起O2反应的内部光谱探针的作用，并成为促进H2O2损失的质子源。由充当质子源的配体进行配位可能是天然双核铁酶用来推动其反应通过过氧双铁水平中间体的一种结构机制。

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