a mini-chromosome maintenance protein, essential for the initiation of eukaryotic genome replication. The MCM hexameric protein complex is a key component of the pre-replication complex. The complex consisting of this protein and MCM2, 6 and 7 possesses DNA helicase activity. Phosphorylation by CDC2 reduces the DNA helicase activity and chromatin binding of the complex. Note: This description may include information from UniProtKB.