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. Author manuscript; available in PMC: 2021 Apr 1.
Published in final edited form as: Curr Opin Struct Biol. 2019 Nov 26;61:25–32. doi: 10.1016/j.sbi.2019.10.003

Figure 2.

Figure 2.

Structure of hexameric helicases. (a-f) Orthogonal views of hexameric helicase-DNA complexes of gp4 (a-b), E1 (c-d), and CMG (e-f). The N-terminal domains (NTD, or primase (Pri) domain in gp4) are shown as semi-transparent molecular surfaces, and the C-terminal helicase (Hel) domains are shown in cartoons. The subunits in gp4 and E1 are marked as A-F following the order from the 3′-to-5′ end of the DNA and colored in blue, light magenta, green, cyan, yellow, and red, respectively. The MCM subunits in CMG complexes followed the same color scheme while the MCM4 and MCM7 are in light blue and red to indicate that they are not involved in DNA binding. HelF subunits in gp4 and E1 as well as MCM4 and MCM7 in CMG are omitted in panels a, c, e, for clarity. The translocated position of HelF in gp4 are indicated by red outline or oval. The directions of helicase translocation are marked by grey arrows in panel a, c, e. (g) Superposition of DNAs in these helicase complexes with B-DNA (black and grey). (h) The hand-over-hand translocation mechanism of hexameric helicase base on gp4 helicase structures.