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 S-phase checkpoint activation upon UV-induced damage. ATP + H2O = ADP + H(+) + phosphate Component of the MCM2-7 complex (PubMed:9305914, PubMed:16899510, PubMed:17296731). The complex forms a toroidal hexameric ring with the proposed subunit order MCM2-MCM6-MCM4-MCM7-MCM3-MCM5 (PubMed:9305914, PubMed:16899510, PubMed:17296731). Interacts with the ATR-ATRIP complex and with RAD17 (PubMed:15210935, PubMed:15538388). Interacts with TIPIN (PubMed:17116885). Interacts with MCMBP (PubMed:17296731). Interacts with ANKRD17 (PubMed:23711367). Component of the replisome complex composed of at least DONSON, MCM2, MCM7, PCNA and TICRR (PubMed:28191891). 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. O-glycosylated (O-GlcNAcylated), in a cell cycle-dependent manner. Ubiquitinated by traip when forks converge following formation of DNA interstrand cross-links. Short ubiquitin chains on MCM7 promote recruitment of DNA glycosylase NEIL3. If the interstrand cross-link cannot be cleaved by NEIL3, the ubiquitin chains continue to grow on MCM7, promoting the unloading of the CMG helicase complex by the VCP/p97 ATPase. Early fractionation of eukaryotic MCM proteins yielded a variety of dimeric, trimeric and tetrameric complexes with unclear biological significance. Specifically a MCM467 subcomplex is shown to have in vitro helicase activity which is inhibited by the MCM2 subunit. The MCM2-7 hexamer is the proposed physiological active complex. Belongs to the MCM family.