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. Author manuscript; available in PMC: 2022 May 13.
Published in final edited form as: DNA Repair (Amst). 2017 May 20;55:76–82. doi: 10.1016/j.dnarep.2017.05.005

Figure 1. Models of hexameric helicase activation and unwinding.

Figure 1.

A double hexamer MCM complex forms with the N-terminal domain (NTD) head to head at the origin of replication where single-stranded DNA selection and unwinding can proceed either with the A) NTD or B) C-terminal domain (CTD) leading the way. During active unwinding, the MCM helicase proceeds in the 3′-5′ direction on the translocating strand C) excluding single-stranded DNA from the central channel that can D) interact on the exterior surface to control the unwinding rate and efficiency. E) A modification of these models includes initial double-stranded DNA separation occurring within the central channel.