Crystal structure of a near-full-length archaeal MCM: Functional insights for an AAA plus hexameric helicase
Crystal structure of a near-full-length archaeal MCM: Functional insights for an AAA plus hexameric helicase
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DOI：
10.1073/pnas.0808037105
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发表时间：
2008-12-23
影响因子：
11.1
通讯作者：
Chen, Xiaojiang S.
中科院分区：
文献类型：
--
作者：
Brewster, Aaron S.;Wang, Ganggang;Chen, Xiaojiang S.
微小染色体维持蛋白（MCM）复合物是真核生物和微生物DNA复制所必需的复制解旋酶。而真核复合体由6个同源蛋白（MCM 2 -7）组成，古菌硫磺硫化叶菌只有1个MCM蛋白（ssoMCM），其中6个亚基形成一个homohexamer。在这里，我们报告一个4.35埃的晶体结构的近全长ssoMCM。该结构显示出一个细长的折叠，5个亚结构域被组织成2个大的N-和C-末端结构域。一个近全长ssoMCM六聚体的基础上产生的N-末端嗜热甲烷杆菌（mtMCM）六聚体的6倍对称性显示适合键合接触，包括周围的ATP口袋的接口的亚基间的距离。每个亚基的四个不寻常的β-发夹位于六聚体的中央通道内或侧通道周围。此外，六聚体很好地拟合到mtMCM的双六聚体EM图中。我们对亚基间界面和侧通道周围残基的突变分析表明了它们对六聚化和解旋酶功能的关键作用。这些结构和生化结果为进一步研究古菌和真核生物MCM复合物在DNA复制中的解旋酶机制提供了基础。
The minichromosome maintenance protein (MCM) complex is an essential replicative helicase for DNA replication in Archaea and Eukaryotes. Whereas the eukaryotic complex consists of 6 homologous proteins (MCM2-7), the archaeon Sulfolobus solfataricus has only 1 MCM protein (ssoMCM), 6 subunits of which form a homohexamer. Here, we report a 4.35-angstrom crystal structure of the near-full-length ssoMCM. The structure shows an elongated fold, with 5 subdomains that are organized into 2 large N- and C-terminal domains. A near-full-length ssoMCM hexamer generated based on the 6-fold symmetry of the N-terminal Methanothermobacter thermautotrophicus (mtMCM) hexamer shows intersubunit distances suitable for bonding contacts, including the interface around the ATP pocket. Four unusual beta-hairpins of each subunit are located inside the central channel or around the side channels in the hexamer. Additionally, the hexamer fits well into the double-hexamer EM map of mtMCM. Our mutational analysis of residues at the intersubunit interfaces and around the side channels demonstrates their critical roles for hexamerization and helicase function. These structural and biochemical results provide a basis for future study of the helicase mechanisms of the archaeal and eukaryotic MCM complexes in DNA replication.