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. ATP + H2O = ADP + H(+) + phosphate Component of the MCM2-7 complex (PubMed:17296731, PubMed:16899510). The complex forms a toroidal hexameric ring with the proposed subunit order MCM2-MCM6-MCM4-MCM7-MCM3-MCM5 (PubMed:17296731, PubMed:16899510). Interacts with ANKRD17 (PubMed:23711367). Interacts with MCMBP (PubMed:17296731). Component of the CMG helicase complex, composed of the MCM2-7 complex, the GINS complex and CDC45 (By similarity). Interacts with TONSL; the interaction is direct (PubMed:26527279). Associated with chromatin before the formation of nuclei and detaches from it as DNA replication progresses. The disease is caused by variants affecting the gene represented in this entry. Early fractionation of eukaryotic MCM proteins yielded a variety of dimeric, trimeric and tetrameric complexes with unclear biological significance. The MCM2-7 hexamer is the proposed physiological active complex. Belongs to the MCM family.