8-Oxoguanine-DNA N -glycosylase (OGG1) is a eukaryotic DNA repair enzyme responsible for the removal of 8-oxoguanine (oxoG), one of the most abundant oxidative DNA lesions. OGG1 catalyzes two successive reactions - N -gly-cosidic bond hydrolysis (glycosylase activity) and DNA strand cleavage on the 3’-side of the lesion by ß-elimination (lyase activity). The enzyme also exhibits lyase activity with substrates containing apurinic/apyrimidinic (AP) sites (deoxyribose moieties lacking the nucleobase). OGG1 is highly specific for the base opposite the lesion, efficiently excising oxoG and cleaving AP sites located opposite to C, but not opposite to A. The activity is also profoundly decreased by amino acid changes that sterically interfere with oxoG binding in the active site of the enzyme after the lesion is everted from the DNA duplex. Earlier, the molecular dynamics approach was used to study the conformational dynamics of such human OGG1 mutants in complexes with the oxoG:C-containing substrate DNA, and the population density of certain conformers of two OGG1 catalytic residues, Lys249 and Asp268, was suggested to determine the enzyme activity. Here, we report the study of molecular dynamics of human OGG1 bound to the oxoG:A-containing DNA and OGG1 mutants bound to the AP:C-con-taining DNA. We showed that the enzyme low activity is associated with a decrease in the populations of Lys249 and Asp268 properly configured for catalysis. The experimentally measured rate constants for the OGG1 mutants show a good agreement with the models. We conclude that the enzymatic activity of OGG1 is determined majorly by the population density of the catalytically competent conformations of the active site residues Lys249 and Asp268.

中文翻译：

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人 8-Oxoguanine-DNA 糖基化酶活性位点的催化构象

8-氧鸟嘌呤-DNA N-糖基化酶 (OGG1) 是一种真核 DNA 修复酶，负责去除 8-氧鸟嘌呤 (oxoG)，这是最丰富的氧化性 DNA 损伤之一。OGG1 催化两个连续的反应 - N-糖苷键水解（糖基化酶活性）和通过 β-消除（裂解酶活性）在病变 3' 侧进行 DNA 链切割。该酶还表现出对含有无嘌呤/无嘧啶 (AP) 位点（缺乏核碱基的脱氧核糖部分）的底物的裂解酶活性。OGG1 对病变对面的碱基具有高度特异性，可有效切除 oxoG 并切割位于 C 对面但不与 A 相对的 AP 位点。 氨基酸变化也显着降低了活性位点中的 oxoG 结合的氨基酸变化。损伤后的酶从 DNA 双链体中外翻。早些时候，分子动力学方法用于研究与含 oxoG:C 的底物 DNA 复合的此类人类 OGG1 突变体的构象动力学，并建议使用两个 OGG1 催化残基 Lys249 和 Asp268 的某些构象异构体的种群密度来确定酶活性。在这里，我们报告了人类 OGG1 与包含 oxoG:A 的 DNA 和 OGG1 突变体与包含 AP:C 的 DNA 结合的分子动力学的研究。我们发现酶的低活性与正确配置用于催化的 Lys249 和 Asp268 的数量减少有关。OGG1 突变体的实验测量速率常数显示出与模型的良好一致性。