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. Author manuscript; available in PMC: 2018 Feb 6.
Published in final edited form as: Adv Exp Med Biol. 2017;1042:207–228. doi: 10.1007/978-981-10-6955-0_10

Fig. 10.5.

Fig. 10.5

CMG helicase alternates between tilted (extended) and untilted (compact) conformations. (a) Side view of CMG conformer I (extended) in which the CTD motor ring is tilted relative to the NTD ring. (b) Side view of the CMG in conformer II (compact) with an untilted CTD ring. In panels (a, b), the cryo-EM density map is shown as a semitransparent surface rendering, and the atomic model is shown in cartoon (EMD-6535, EMD-6536, PDB 3JC5, and 3JC7). (c) An oil rig-like pump jack DNA unwinding model. Panel (c) is reproduced in part from Figure 7 in Yuan et al. (2016) with permission. Note that the CTD-tier ring pushing on the dsDNA is only for the purpose of illustration. The pump jack model would still function as a translocase if CMG were oriented with the NTD-tier ring pushing on the dsDNA