AI Article Synopsis
- The MCM complex from the archaeon Methanothermobacter thermautotrophicus serves as a model for studying the eukaryotic MCM2-7 helicase, using advanced electron microscopy to visualize its structure.
- The analysis revealed two different conformations of the MCM complex when treated with DNA and ADP.AlF(x), demonstrating surprising asymmetry and potential large conformational changes within the rings.
- A mechanistic model for helicase activity is suggested, involving ligand-controlled rotation of the AAA+ subunits, highlighting the importance of specific structural features for its function.
Article Abstract
The MCM complex from the archaeon Methanother-mobacter thermautotrophicus is a model for the eukaryotic MCM2-7 helicase. We present electron-microscopy single-particle reconstructions of a DNA treated M.thermautotrophicus MCM sample and a ADP.AlF(x) treated sample, respectively assembling as double hexamers and double heptamers. The electron-density maps display an unexpected asymmetry between the two rings, suggesting that large conformational changes can occur within the complex. The structure of the MCM N-terminal domain, as well as the AAA+ and the C-terminal HTH dom-ains of ZraR can be fitted into the reconstructions. Distinct configurations can be modelled for the AAA+ and the HTH domains, suggesting the nature of the conformational change within the complex. The pre-sensor 1 and the helix 2 insertions, important for the activity, can be located pointing towards the centre of the channel in the presence of DNA. We propose a mechanistic model for the helicase activity, based on a ligand-controlled rotation of the AAA+ subunits.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635305 | PMC |
| http://dx.doi.org/10.1093/nar/gkl708 | DOI Listing |
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