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Nature. 2015 Aug 13;524(7564):186-91. doi: 10.1038/nature14685. Epub 2015 Jul 29.

Structure of the eukaryotic MCM complex at 3.8 Å.

Author information

1
Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
2
1] Division of Life Science, Hong Kong Universityof Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China [2] Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
3
1] Division of Life Science, Hong Kong Universityof Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China [2] Department of Molecular Biology and Genetics, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853, USA.

Abstract

DNA replication in eukaryotes is strictly regulated by several mechanisms. A central step in this replication is the assembly of the heterohexameric minichromosome maintenance (MCM2-7) helicase complex at replication origins during G1 phase as an inactive double hexamer. Here, using cryo-electron microscopy, we report a near-atomic structure of the MCM2-7 double hexamer purified from yeast G1 chromatin. Our structure shows that two single hexamers, arranged in a tilted and twisted fashion through interdigitated amino-terminal domain interactions, form a kinked central channel. Four constricted rings consisting of conserved interior β-hairpins from the two single hexamers create a narrow passageway that tightly fits duplex DNA. This narrow passageway, reinforced by the offset of the two single hexamers at the double hexamer interface, is flanked by two pairs of gate-forming subunits, MCM2 and MCM5. These unusual features of the twisted and tilted single hexamers suggest a concerted mechanism for the melting of origin DNA that requires structural deformation of the intervening DNA.

PMID:
26222030
DOI:
10.1038/nature14685
[Indexed for MEDLINE]

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