The Helicase Activity of Hyperthermophilic Archaeal MCM is Enhanced at High Temperatures by Lysine Methylation.
The Helicase Activity of Hyperthermophilic Archaeal MCM is Enhanced at High Temperatures by Lysine Methylation.
复制标题
赖氨酸甲基化在高温下增强超嗜热古菌 MCM 的解旋酶活性
DOI：
10.3389/fmicb.2015.01247
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发表时间：
2015
影响因子：
5.2
通讯作者：
Cao Q
中科院分区：
文献类型：
--
作者：
Xia Y;Niu Y;Cui J;Fu Y;Chen XS;Lou H;Cao Q
赖氨酸甲基化和甲基转移酶广泛存在于生命的第三个领域，古细菌。然而，甲基化对古生菌蛋白的影响还有待确定。在这里，我们报道重组sisMCM，真核生物Mcm2-7复制解旋酶的古细菌同源物，在体外被aKMT4甲基化。质谱表明，这些赖氨酸残基的单甲基化发生在从超嗜热的岛硫虫细胞中纯化的内源性sisMCM蛋白中。甲基化刺激了迷你染色体维持（MCM）的解旋酶活性，特别是在超过70°C的温度下。甲基化的MCM在76 ~ 82℃的温度下热处理后，DNA解绕活性最佳，这与超嗜热菌Sulfolobus的典型生长温度密切相关。甲基化后，MCM解旋酶在80℃下的半衰期显著延长。甲基化位点位于可接近的蛋白质表面，可能通过改变疏水性和表面电荷来调节分子内和分子间的相互作用。此外，MCM的甲基化模拟突变体显示出与甲基化MCM相当的耐热解旋酶活性。这些数据提供的生化证据表明，翻译后修饰，如甲基化可能提高蛋白质在高温下的动力学稳定性。
Lysine methylation and methyltransferases are widespread in the third domain of life, archaea. Nevertheless, the effects of methylation on archaeal proteins wait to be defined. Here, we report that recombinant sisMCM, an archaeal homolog of Mcm2-7 eukaryotic replicative helicase, is methylated by aKMT4 in vitro. Mono-methylation of these lysine residues occurs coincidently in the endogenous sisMCM protein purified from the hyperthermophilic Sulfolobus islandicus cells as indicated by mass spectra. The helicase activity of mini-chromosome maintenance (MCM) is stimulated by methylation, particularly at temperatures over 70°C. The methylated MCM shows optimal DNA unwinding activity after heat-treatment between 76 and 82°C, which correlates well with the typical growth temperatures of hyperthermophilic Sulfolobus. After methylation, the half life of MCM helicase is dramatically extended at 80°C. The methylated sites are located on the accessible protein surface, which might modulate the intra- and inter- molecular interactions through changing the hydrophobicity and surface charge. Furthermore, the methylation-mimic mutants of MCM show heat resistance helicase activity comparable to the methylated MCM. These data provide the biochemical evidence that posttranslational modifications such as methylation may enhance kinetic stability of proteins under the elevated growth temperatures of hyperthermophilic archaea.