sentences:  Each hexameric Mcm2-7 ring first serves as the scaffold for the assembly of the replisome and then as the core of the catalytic CMG (Cdc45-MCM-GINS) helicase, which is a main component of the replisome.Each Mcm protein is highly related to all others, but unique sequences distinguishing each of the subunit types are conserved across eukaryotes.All eukaryotes have exactly six Mcm protein analogs that each fall into one of the existing classes (Mcm2-7), indicating that each Mcm protein has a unique and important function.