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 (By similarity). Required for the progression of S phase. ATP + H2O = ADP + H(+) + phosphate Component of the mcm2-7 complex. The complex forms a toroidal hexameric ring with the proposed subunit order mcm2-mcm6-mcm4-mcm7-mcm3-mcm5 (Probable). The heterodimers of mcm4/mcm6 and mcm3/mcm5 interact with mcm2 and mcm7. Interacts with sld3 and mcm10. Belongs to the MCM family.