The CMG (Cdc45-MCM-GINS) complex is the eukaryotic replicative helicase, the enzyme that unwinds double-stranded DNA at replication forks. It is a macromolecular assembly of three replication factors: the Cdc45 protein, and the MCM and GINS complexes. All three components are essential for CMG function, with the MCM2-7 complex functioning as the molecular motor that harnesses the energy of ATP hydrolysis to catalyse strand separation. (Adapted from PMID:23412083.)