 A near-atomic resolution model of the entire ORC-Cdc6-Cdt1-Mcm2-7 (OCCM) complex with DNA was assembled from EM data in 2017.It is thought that the CDC6-Cdt1 complex uses ATP hydrolysis to thread DNA through the central hole of the MCM doughnut.Mutations in the binding motif of CDC6 strongly suggest that ATP binding and hydrolysis is essential for its function.