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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A double-hexamer archaeal minichromosome maintenance protein is an ATP-dependent DNA helicase
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A double-hexamer archaeal minichromosome maintenance protein is an ATP-dependent DNA helicase

机译：双六聚体古细菌微染色体维持蛋白是ATP依赖的DNA解旋酶

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摘要

The minichromosome maintenance (MCM) proteins are essential for DNA replication in eukaryotes. Thus far. all eukaryotes have been shown to contain six highly reIated MCMs that apparently function together in DNA replication. Sequencing of the entire genome of the thermophilic archaeon MethanobaCtrrium thermo- autotrophicum has allowed us to identify only a single MCM-like gene (ORF Mt1770). This gene is most similar to MCM4 in eukary- otic cells. Here we have expressed and purified the M. thermoau- totrophicum MCM protein. The purified protein forms a complex that has a molecular mass of rs850 kDa, consistent with formation of a double hexamer. The protein has an ATP-independent DNA- binding activity, a DNA-stimulated ATPase activity that discrimi- nates between single- and double-stranded DNA. and a strand- displacement (helicase) activity that can unwind up to 500 base pairs. The 3' to S' helicase activity requires both ATP hydrolysis and a functional nucleotide-binding site. Moreover. the double hex- amer form is the actve heticase. It is therefore likely that an MCM complex acts as the replicative DNA helicase in eukaryotes and archaea. The simplified replication machinery in archaea may provide a simplified model for assembly of the machinery required for initiation of eukaryotic DNA replication.
机译：微型染色体维持（MCM）蛋白对于真核生物中DNA复制至关重要。迄今。已显示所有真核生物均包含六个高度相关的MCM，它们显然在DNA复制中共同起作用。嗜热古细菌MethanobaCtrrium thermo-autotrophicum的整个基因组的测序已使我们只能鉴定单个MCM样基因（ORF Mt1770）。该基因与真核细胞中的MCM4最相似。在这里，我们表达并纯化了嗜热毁丝霉MCM蛋白。纯化的蛋白质形成分子量为rs850 kDa的复合物，与双六聚体的形成一致。该蛋白质具有不依赖ATP的DNA结合活性，这种DNA刺激的ATPase活性可区分单链和双链DNA。链置换（解旋酶）活性最多可以解开500个碱基对。 3'至S'解旋酶活性需要ATP水解和功能性核苷酸结合位点。此外。双六聚体形式是actve脱氢酶。因此，MCM复合物很可能在真核生物和古细菌中充当复制性DNA解旋酶。古细菌中的简化的复制机制可以为组装真核DNA复制所需的机制提供简化的模型。

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