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. Author manuscript; available in PMC: 2018 Mar 7.
Published in final edited form as: Cell. 2017 Jun 29;170(1):48–60.e11. doi: 10.1016/j.cell.2017.06.012

Figure 5. Nature of the seed sequence bubble unwound by TfuCascade.

Figure 5

A. B. Two different views of the TfuCascade/seed-bubble cryo-EM structure highlighting the bending at the PAM region, extent of the seed-bubble, and the paths of the target and non-target strands. Type 2 class is illustrated here to emphasize the path of the non-target strand. C. Function of Q-wedge, L3-loop and Cas7.4 K-vise in shaping the path of the seed-bubble. D. Inclusion of a post-seed-bubble dsDNA to model the entire DNA substrate in the TfuCascade/seed-bubble complex. DNA bending around the PAM region likely plays an important role in melting dsDNA into a seed-bubble. E. DNA substrate follows a distinct path in the seed-bubble and full R-loop states. Note the differences in directionality, curvature, and DNA bending angle. F. Alanine substitution in K-vise reduced the target DNA binding affinity of TfuCascade by ~5-fold.