title: Structural polymorphism of Methanothermobacter thermautotrophicus MCM.
abstract: The minichromosome maintenance (MCM) proteins are essential for replication initiation and elongation in eukarya and archaea. There are six MCM proteins in eukaryotes, and MCM complexes are believed to unwind DNA during chromosomal DNA replication. However, the mechanism and structure of the MCM complexes are not known. Only one MCM is found in the archaeon Methanothermobacter thermautotrophicus (mtMCM), and this provides a simpler system for study. The crystal structure of a mtMCM N-terminal fragment has been solved, but surprisingly only subtle structural changes were seen between the wild-type protein and one having a mutation corresponding to the yeast MCM5 bob1 mutation. The bob1 mutation bypasses the phosphorylation required for activation of MCM in yeast. We have used electron microscopy and three-dimensional reconstruction to examine a number of different fragments of mtMCM, and can visualize a large conformational change within the N-terminal fragment. This offers new insight into the conformational dynamics of MCM and the phosphorylation-bypass phenotype in yeast.
authors.affiliation: Department of Biochemistry and Molecular Genetics, Box 800733, University Of Virginia Health Sciences Center, Charlottesville, VA 22908, USA.
authors.forename: Yen-Ju
authors.initials: YJ
authors.lastname: Chen
authors.forename: Xiong
authors.initials: X
authors.lastname: Yu
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kasiviswanathan
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Shin
authors.forename: Zvi
authors.initials: Z
authors.lastname: Kelman
authors.forename: Edward H
authors.initials: EH
authors.lastname: Egelman
mesh_terms: D018360:Crystallography, X-Ray; D017013:Methanobacteriaceae / Q000737:chemistry* / Q000235:genetics; D008854:Microscopy, Electron; D008958:Models, Molecular; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry; D010766:Phosphorylation; D011487:Protein Conformation; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D010446:Peptide Fragments; D014157:Transcription Factors