8p63 | pdb_00008p63
S. cerevisiae consensus-sCMGE on ssDNA after DNA replication initiation
Structural highlights
FunctionMCM3_YEAST Acts as component of the MCM2-7 complex (MCM complex) which is the putative replicative helicase essential for 'once per cell cycle' DNA replication initiation and elongation in eukaryotic cells. The active ATPase sites in the MCM2-7 ring are formed through the interaction surfaces of two neighboring subunits such that a critical structure of a conserved arginine finger motif is provided in trans relative to the ATP-binding site of the Walker A box of the adjacent subunit. The six ATPase active sites, however, are likely to contribute differentially to the complex helicase activity. Once loaded onto DNA, double hexamers can slide on dsDNA in the absence of ATPase activity. Necessary for cell growth.[1] [2] Publication Abstract from PubMedTo prevent detrimental chromosome re-replication, DNA loading of a double hexamer of the minichromosome maintenance (MCM) replicative helicase is temporally separated from DNA unwinding. Upon S-phase transition in yeast, DNA unwinding is achieved in two steps: limited opening of the double helix and topological separation of the two DNA strands. First, Cdc45, GINS and Polepsilon engage MCM to assemble a double CMGE with two partially separated hexamers that nucleate DNA melting. In the second step, triggered by Mcm10, two CMGEs separate completely, eject the lagging-strand template and cross paths. To understand Mcm10 during helicase activation, we used biochemical reconstitution with cryogenic electron microscopy. We found that Mcm10 splits the double CMGE by engaging the N-terminal homo-dimerization face of MCM. To eject the lagging strand, DNA unwinding is started from the N-terminal side of MCM while the hexamer channel becomes too narrow to harbor duplex DNA. Unwinding of a eukaryotic origin of replication visualized by cryo-EM.,Henrikus SS, Gross MH, Willhoft O, Puhringer T, Lewis JS, McClure AW, Greiwe JF, Palm G, Nans A, Diffley JFX, Costa A Nat Struct Mol Biol. 2024 May 17. doi: 10.1038/s41594-024-01280-z. PMID:38760633[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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