Pumps, paradoxes and ploughshares: Mechanism of the MCM2-7 DNA helicase

Tatsuro S. Takahashi, Dale B. Wigley, Johannes C. Walter

Research output: Contribution to journalArticlepeer-review

130 Citations (Scopus)


In eukaryotes, numerous lines of evidence have coalesced into a convincing case that the MCM2-7 complex - a heterohexameric ATPase - is the replicative DNA helicase. However, almost nothing is known about how this enzyme functions in a cellular context. Some models for the mechanism of the MCM2-7 helicase envision that it translocates along single-stranded DNA (ssDNA), whereas, more recently, it is has been suggested that it pumps double-stranded DNA (dsDNA) through its central channel. In particular, one model in which a double hexamer of MCM2-7 pumps dsDNA towards the hexamer interface and extrudes ssDNA laterally as a result of torsional strain is gaining popularity. Here, we discuss existing models and propose a new variation in which a single hexamer is the functional unit of the helicase. Duplex DNA is pumped into MCM2-7 and, as it emerges from the complex, a rigid protein that we term the 'ploughshare' splits the duplex.

Original languageEnglish
Pages (from-to)437-444
Number of pages8
JournalTrends in Biochemical Sciences
Issue number8
Publication statusPublished - Aug 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology


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