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首页> 外文期刊>Biochemistry >Resonance Raman spectral properties of FMN of bovine heart NADH:ubiquinone oxidoreductase suggesting a mechanism for the prevention of spontaneous production of reactive oxygen species
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Resonance Raman spectral properties of FMN of bovine heart NADH:ubiquinone oxidoreductase suggesting a mechanism for the prevention of spontaneous production of reactive oxygen species

机译：牛心脏NADH：泛醌氧化还原酶的FMN的共振拉曼光谱性质表明了一种预防活性氧自发产生的机制

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摘要

A highly improved method for obtaining resonance Raman (RR) spectra provided spectra comparable to the best known flavoprotein spectra when the method was tested using bovine heart NADH:ubiquinone oxidoreductase (Complex I), a protein with a molecular mass of 1000 kDa, which causes the level of RR noise to be 1 order of magnitude higher than for most flavoproteins. The FMN RR band shift (1631/1633 cm~(-1)) and the increase in the magnitude of the band at 1252 cm-1 upon binding to Complex I suggest hydrogen bond formation involving one of the C-O groups [C(2)-O] of isoalloxazine to stabilize its quinoid form. This lowers the redox potential of FMN and the electron density of the O_2 binding site [a carbon atom, C(4a)] in the reduced form. Thus, spontaneous production of reactive oxygen species at the FMN site is prevented by minimizing the duration of the fully reduced state by accelerating the FMN oxidation and by weakening the O_2 affinity of C(4a). Other band shifts (1258/1252 cm-1 and 1161/1158 cm-1) suggest a significantly weaker hydrogen bond to the NH group [N(3)-H] of isoalloxazine. This result, together with the reported X-ray structure in which N(3)-H is surrounded by negatively charged surface without hydrogen bond formation, suggests that N(3)-H is weakly but significantly polarized. The polarized N(3)-H, adjacent to the C(2)-O group, stabilizes the polarized state of C(2)-O to strengthen the hydrogen bond to C(2)-O. This could fine-tune the hydrogen bond strength. Other results show a high-dielectric constant environment and weak hydrogen bonds to the isoalloxazine, suggesting adaptability for various functional controls.
机译：当使用牛心NADH：泛醌氧化还原酶（复合物I）（分子量为1000 kDa的蛋白质）进行测试时，一种获得共振拉曼（RR）光谱的经过高度改进的方法所提供的光谱与最著名的黄素蛋白质光谱相当。 RR噪声的水平比大多数黄素蛋白高1个数量级。 FMN RR带移（1631/1633 cm〜（-1））和与复合物I结合后1252 cm-1处带的强度增加表明氢键形成涉及一个CO基团[C（2） -O]的异四恶嗪稳定其醌型。这降低了FMN的氧化还原电位和还原形式的O_2结合位点[碳原子，C（4a）]的电子密度。因此，通过加速FMN的氧化并削弱C（4a）的O_2亲和力，可以最大限度地减少完全还原态的持续时间，从而防止FMN处活性氧的自发产生。其他的谱带位移（1258/1252 cm-1和1161/1158 cm-1）表明与异恶嗪的NH基团[N（3）-H]的氢键明显弱得多。该结果与已报道的X射线结构（其中N（3）-H被带负电荷的表面包围而没有氢键形成）表明N（3）-H弱但明显极化。与C（2）-O基团相邻的极化N（3）-H稳定了C（2）-O的极化态，从而增强了与C（2）-O的氢键。这可以微调氢键强度。其他结果表明，高介电常数环境和与异四恶嗪的氢键弱，表明对各种功能控件的适应性。

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