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. Author manuscript; available in PMC: 2014 Sep 6.
Published in final edited form as: Nature. 2014 Jan 29;507(7490):62–67. doi: 10.1038/nature13011

Figure 4. PAM recognition regulates Cas9 nuclease activity.

Figure 4

a, Cleavage assay with single-stranded, double-stranded, and partially double-stranded substrates. b, Relative affinities and cleavage rates; (mean ± s.d.). c, Model for target search, recognition and cleavage by Cas9:RNA. The search initiates through random 3D collisions. Cas9:RNA rapidly dissociates from non-PAM DNA, but binds PAMs for longer times and samples adjacent DNA for guide RNA complementarity, giving rise to a heterogeneous population of intermediates. At correct targets, Cas9:RNA initiates formation of an RNA:DNA heteroduplex, and R-loop expansion propagates via sequential unwinding. The DNA is cleaved and Cas9:RNA remains bound to the cleaved products.