Structural basis of the Methanothermobacter thermautotrophicus MCM helicase activity.
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.
Costa
Alessandro
A
Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, SW7 2AZ, UK.
Pape
Tillmann
T
van Heel
Marin
M
Brick
Peter
P
Patwardhan
Ardan
A
Onesti
Silvia
S
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
D019843:Archaeal Proteins; D004247:DNA; D000251:Adenosine Triphosphatases; D004265:DNA Helicases