title: Structural basis of the Methanothermobacter thermautotrophicus MCM helicase activity.
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.
authors.affiliation: Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, SW7 2AZ, UK.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Costa
authors.forename: Tillmann
authors.initials: T
authors.lastname: Pape
authors.forename: Marin
authors.initials: M
authors.lastname: van Heel
authors.forename: Peter
authors.initials: P
authors.lastname: Brick
authors.forename: Ardan
authors.initials: A
authors.lastname: Patwardhan
authors.forename: Silvia
authors.initials: S
authors.lastname: Onesti
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D004247:DNA / Q000737:chemistry; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D017013:Methanobacteriaceae / Q000201:enzymology*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
chemical_list: D019843:Archaeal Proteins; D004247:DNA; D000251:Adenosine Triphosphatases; D004265:DNA Helicases