FIGURE 5.

A proposed mechanism of target DNA recognition and its cleavage by the CRISPR/Cas9 system. (A) Large conformational rearrangement occurs in Cas9 upon sgRNA loading to achieve a target‐recognition mode. Apo‐Cas9 consists of a PAM‐interacting cleft, largely disordered, that becomes prestructured for PAM sampling. (B) The guide RNA seed is preorganized for interrogation of adjacent DNA for guide RNA complementarity. (C) A coordinated multiple steps further activate Cas9, starting with PAM recognistion. (D) Local DNA melting, RNA strand invasion and (E) subsequent R‐loop formation. (F) A conformational change of the HNH domain allosterically regulates the RuC domain, ensuring concerted DNA cleavage. Abbreviations: CRISPR, clustered regularly interspaced short palindromic repeats; Rec, recognition; Nuc, nuclease; sgRNA, single‐guide RNA; PAM, protospacer adjacent motif