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. Required for DNA replication and cell proliferation (By similarity). 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 (By similarity). Associated with the replication-specific DNA polymerase alpha (By similarity). Interacts with MCMBP. Interacts with ANKRD17 (By similarity). Interacts with MCM3AP; this interaction leads to MCM3 acetylation (By similarity). Component of the CMG helicase complex, composed of the MCM2-7 complex, the GINS complex and CDC45 (By similarity). Associated with chromatin before the formation of nuclei and detaches from it as DNA replication progresses. Acetylated by MCM3AP. Belongs to the MCM family.