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. Author manuscript; available in PMC: 2014 Oct 3.
Published in final edited form as: Science. 2014 Feb 6;343(6176):1247997. doi: 10.1126/science.1247997

Fig. 8. Model for RNA-induced conversion of Cas9 into a structurally activated DNA surveillance complex.

Fig. 8

Upon binding the crRNA:tracrRNA guide, the two structural lobes of Cas9 reorient such that the two nucleic acid binding clefts face each other. This generates a central DNA binding channel, which allows access to dsDNA. Target DNA binding in the central channel and PAM-dependent R-loop formation result in a further structural rearrangement. Here, the nuclease domain lobe undergoes further rotation relative to the α-helical lobe, fully enclosing the DNA target, and the two nuclease domains engage both DNA strands for cleavage.