An O-Centered Structure of the Trinuclear Copper Center in the Cys500Ser/Glu506Gln Mutant of CueO and Structural Changes in Low to High X-Ray Dose Conditions
An O-Centered Structure of the Trinuclear Copper Center in the Cys500Ser/Glu506Gln Mutant of CueO and Structural Changes in Low to High X-Ray Dose Conditions
复制标题
DOI：
10.1002/anie.201107739
复制
发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Sakurai, Takeshi
中科院分区：
文献类型：
--
作者：
Komori, Hirofumi;Sugiyama, Ryosuke;Sakurai, Takeshi
CueO是一种参与大肠杆菌铜外排系统的多铜氧化酶（MCO）。[1，2] CueO中的I型铜（T1 Cu）介导了电子从基底转移到三核铜中心（TNC）的过程，TNC由II型铜位点（T2 Cu）和一对III型铜位点（T3 Cus（T3 aCu和T3 bCu））组成。最后的电子受体O2与TNC结合并被还原成两个水分子。[3-6]特别注意了MCO的O2还原机制，以避免形成或释放活性氧物种。只有末端氧化酶如细胞色素c氧化酶催化这一过程，除了MCO。因此，MCO有望作为阴极酶应用于生物燃料电池。在四电子O2还原过程中发现了两种反应中间体，称为中间体I（过氧化物中间体）和中间体II（天然中间体）（图1）。中间体I可以在MCO衍生物的反应过程中被捕获，例如：在T1 Cu中心的Hg取代的漆酶，[7]具有二价铜态的T1 Cu和亚铜态的T2 Cu和T3 Cus的混合价漆酶，[8] CueO，[9]胆红素氧化酶，[10]和Fet 3 p，[11]，其中T1 Cu位点由于Cys配体被Ser取代而空缺。由于中间体I不具有电子顺磁共振（EPR）信号（支持性信息中的图S1），[7-11]有人提出，过氧化物以μ-1，2-过氧基离子的形式与TNC结合，因此，三个铜离子中的一个保持亚铜状态。然而，支持过氧化物存在或TNC中铜中心氧化态的直接证据尚未发表。因此
CueO is a multicopoper oxidase (MCO) involved in the copper efflux system of Escherichia coli.[1, 2] The type I copper (T1Cu) in CueO mediates the process of electron transfer from the substrate to the trinuclear copper center (TNC) which is composed of a type II copper site (T2Cu) and a pair of type III copper sites (T3Cus (T3aCu and T3bCu)). O2, the final electron acceptor, binds to the TNC and is reduced to two water molecules.[3-6] Special attention has been paid on this O2 reduction mechanism of MCO to avoid to form or to release activated oxygen species. Only terminal oxidases such as cytochrome c oxidase catalyze this process except MCOs. Thus, MCOs have been expected to apply to biofuel cells as a cathodic enzyme. Two reaction intermediates in the four-electron O2 reduction process have been discovered and are known as, the intermediate I (peroxide intermediate) and intermediate II (native intermediate)(Figure 1). Intermediates I can be trapped during the course of reactions of the MCO derivatives such as: the Hg-substituted laccase at the T1Cu center,[7] the mixed valent laccase with T1Cu in the cupric state and T2Cu and T3Cus in the cuprous state,[8] CueO,[9] bilirubin oxidase,[10] and Fet3p,[11] in which the T1Cu site is vacant as a result of the replacement of the Cys ligand with Ser. Since the intermediate I does not have an electron paramagnetic resonance (EPR) signal (Figure S1 in Supporting Information),[7-11] it has been proposed that a peroxide species is bound to the TNC in a μ-1, 2-peroxofashion, and accordingly, one of the three copper ions remains in the cuprous state. However, direct evidence to support the presence of peroxide or the oxidation state of the copper centers in the TNC has not been published. Thus, it