(S. pombe) is notably different from that of other eukaryotes; Cdc6 is replaced by the homologous Cdc18 protein. Sap1 is also included in the S. pombe pre-RC because it is required for Cdc18 binding. The pre-RC of Xenopus laevis (X. laevis) also has an additional protein, MCM9, which helps load the MCM heterohexamer onto the origin of replication. The structure of the ORC, MCM, as well as the intermediate ORC-Cdc6-Cdt1-Mcm2-7 (OCCM) complex has been resolved.

Recognition of the origin of replication