An extended N-H bond, driven by a conserved second-order interaction, orients the flavin N5 orbital in cholesterol oxidase.
An extended N-H bond, driven by a conserved second-order interaction, orients the flavin N5 orbital in cholesterol oxidase.
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DOI：
10.1038/srep40517
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发表时间：
2017-01-18
影响因子：
4.6
通讯作者：
Vrielink A
中科院分区：
文献类型：
--
作者：
Golden E;Yu LJ;Meilleur F;Blakeley MP;Duff AP;Karton A;Vrielink A
黄素酶中黄素辅因子周围的蛋白质微环境是这类酶催化反应的效率和多样性的关键。氧化还原酶黄素酶的X-射线衍射结构揭示了促进催化的经常性特征，例如主链氮原子和黄素氧化还原中心（N5）之间的氢键。胆固醇氧化酶的中子衍射研究揭示了一个不寻常的延长的主链氮氢键距离定位的氢原子对黄素N5反应中心。调查的结构特征，可能会导致这种不寻常的发生揭示了一个带正电荷的赖氨酸侧链，保守在其他黄素介导的氧化还原酶，在第二个壳远离FAD辅因子的作用，通过与羰基氧原子的相互作用，以取代肽键。双杂化密度泛函理论计算证实，这种静电安排影响的N-H键长的黄素反应中心的区域。我们提出了一种新的二阶部分电荷相互作用网络，使N5的氢化物接收轨道的正确取向。黄素介导的氧化还原化学这些意见的影响进行了讨论。
The protein microenvironment surrounding the flavin cofactor in flavoenzymes is key to the efficiency and diversity of reactions catalysed by this class of enzymes. X-ray diffraction structures of oxidoreductase flavoenzymes have revealed recurrent features which facilitate catalysis, such as a hydrogen bond between a main chain nitrogen atom and the flavin redox center (N5). A neutron diffraction study of cholesterol oxidase has revealed an unusual elongated main chain nitrogen to hydrogen bond distance positioning the hydrogen atom towards the flavin N5 reactive center. Investigation of the structural features which could cause such an unusual occurrence revealed a positively charged lysine side chain, conserved in other flavin mediated oxidoreductases, in a second shell away from the FAD cofactor acting to polarize the peptide bond through interaction with the carbonyl oxygen atom. Double-hybrid density functional theory calculations confirm that this electrostatic arrangement affects the N-H bond length in the region of the flavin reactive center. We propose a novel second-order partial-charge interaction network which enables the correct orientation of the hydride receiving orbital of N5. The implications of these observations for flavin mediated redox chemistry are discussed.