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:16899510, PubMed:17296731, PubMed:9305914). The complex forms a toroidal hexameric ring with the proposed subunit order MCM2-MCM6-MCM4-MCM7-MCM3-MCM5 (PubMed:16899510, PubMed:17296731, PubMed:9305914). May interact with MCM10 (PubMed:11095689). Interacts with TIPIN (PubMed:17116885). Interacts with CDT1 (PubMed:20202939). Interacts with MCMBP (PubMed:17296731). Interacts with DDI2 (PubMed:29290612). Component of the CMG helicase complex, composed of the MCM2-7 complex, the GINS complex and CDC45 (By similarity). Binds to chromatin during G1 and detach from it during S phase. O-glycosylated (O-GlcNAcylated), in a cell cycle-dependent manner. Intronic variations in MCM6 upstream from the LCT gene are associated with adult-type hypolactasia [MIM:223100] leading to lactose intolerance, or with lactase persistance. Lactose intolerance is a normal physiological phenomenon caused by developmental down-regulation of lactase activity during childhood or early adulthood. A non-coding variation in MCM6 affects the transcriptional regulation of the LCT gene resulting in down-regulation of lactase activity. However, the majority of Northern Europeans and some African populations have the ability to maintain lactase activity and digest lactose throughout life (lactase persistence). 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.